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Apollo 9

Apollo 9 (March 3–13, 1969) was the third human spaceflight in NASA's Apollo program. Flown in low Earth orbit, it was the second crewed Apollo mission that the United States launched via a Saturn V rocket, and was the first flight of the full Apollo spacecraft: the command and service module (CSM) with the Lunar Module (LM). The mission was flown to qualify the LM for lunar orbit operations in preparation for the first Moon landing by demonstrating its descent and ascent propulsion systems, showing that its crew could fly it independently, then rendezvous and dock with the CSM again, as would be required for the first crewed lunar landing. Other objectives of the flight included firing the LM descent engine to propel the spacecraft stack as a backup mode (as would be required on the Apollo 13 mission), and use of the portable life support system backpack outside the LM cabin.

The three-man crew consisted of Commander James McDivitt, Command Module Pilot David Scott, and Lunar Module Pilot Rusty Schweickart. During the ten-day mission, they tested systems and procedures critical to landing on the Moon, including the LM engines, backpack life support systems, navigation systems and docking maneuvers.

After launching on March 3, 1969, the crew performed the first crewed flight of a lunar module, the first docking and extraction of the same, one two-person spacewalk (EVA), and the second docking of two crewed spacecraft—two months after the Soviets performed a spacewalk crew transfer between Soyuz 4 and Soyuz 5. The mission concluded on March 13 and was a complete success. It proved the LM worthy of crewed spaceflight, setting the stage for the dress rehearsal for the lunar landing, Apollo 10, before the ultimate goal, landing on the Moon.

Mission background
In April 1966, McDivitt, Scott, and Schweickart were selected by Director of Flight Crew Operations Deke Slayton as the second Apollo crew. Their initial job was as backup to the first Apollo crew to be chosen, Gus Grissom, Ed White, and Roger Chaffee, for the first crewed Earth orbital test flight of the block I command and service module, designated AS-204. Delays in the block I CSM development pushed AS-204 into 1967. The revised plan had the McDivitt crew scheduled for the second crewed CSM, which was to rendezvous in Earth orbit with an uncrewed LM, launched separately. The third crewed mission, to be commanded by Frank Borman, was to be the first launch of a SaturnV with a crew.

On January 27, 1967, Grissom's crew was conducting a launch-pad test for their planned February 21 mission, which they named Apollo 1, when a fire broke out in the cabin, killing all three men. A complete safety review of the Apollo program followed. During this time Apollo 5 took place, an uncrewed launch to test the first lunar module (LM-1).

Under the new schedule, the first Apollo crewed mission to go into space would be Apollo 7, planned for October 1968. This mission, which was to test the block II command module, did not include a lunar module. In 1967, NASA had adopted a series of lettered missions leading up to the crewed lunar landing, the "G mission", completion of one being a prerequisite to the next. Apollo7 would be the "Cmission", but the "Dmission" required testing of the crewed lunar module, which was running behind schedule and endangering John F. Kennedy's goal of Americans walking on the Moon and returning safely to Earth by the end of the 1960s. McDivitt's crew had been announced by NASA in November 1967 as prime crew for the Dmission, lengthy testing of the command and lunar modules in Earth orbit.

Seeking to keep Kennedy's goal on schedule, in August 1968, Apollo Program Manager George M. Low proposed that if Apollo7 in October went well, Apollo8 would go to lunar orbit without a LM. Until then, Apollo8 was the Dmission with Apollo9 the "E mission", testing in medium Earth orbit. After NASA approved sending Apollo8 to the Moon, while making Apollo9 the Dmission, Slayton offered McDivitt the opportunity to stay with Apollo8 and thus go to lunar orbit. McDivitt turned it down on behalf of his crew, preferring to stay with the Dmission, now Apollo9.

Apollo7 went well, and the crews were switched. The crew swap also affected who would be the first astronauts to land on the Moon, for when the crews for Apollo8 and9 were swapped, so were the backup crews. Since the rule of thumb was for backup crews to fly as prime crew three missions later, this put Neil Armstrong's crew (Borman's backup) in position to make the first landing attempt on Apollo 11 instead of Pete Conrad's crew, who made the second landing on Apollo 12.

Crew and key Mission Control personnel
McDivitt was in the Air Force; selected as a member of the second group of astronauts in 1962, he was command pilot of Gemini 4 (1965). Scott, also Air Force, was selected in the third astronaut group in 1963 and flew alongside Neil Armstrong in Gemini 8, on which the first spacecraft docking was performed. Schweickart, a civilian who had served in the Air Force and Massachusetts Air National Guard, was selected as a Group3 astronaut but was not assigned to a Gemini mission and had no spaceflight experience.

The backup crew consisted of Pete Conrad as commander, Command Module Pilot Richard F. Gordon Jr., and Lunar Module Pilot Alan L. Bean. This crew flew as prime on Apollo 12 in November 1969. The support crew for Apollo9 consisted of Stuart A. Roosa, Jack R. Lousma, Edgar D. Mitchell and Alfred M. Worden. Lousma was not an original member of the Apollo9 support crew, but was assigned after Fred W. Haise Jr. was moved to the position of backup lunar module pilot on Apollo 8—several astronauts were shifted in the wake of Michael Collins being removed from the Apollo8 prime crew because of treatment for bone spurs.

The flight directors were Gene Kranz, first shift, Gerry Griffin, second shift and Pete Frank, third shift. Capsule communicators were Conrad, Gordon, Bean, Worden, Roosa and Ronald Evans.

Mission insignia

The circular patch shows a drawing of a Saturn V rocket with the letters USA on it. To its right, an Apollo CSM is shown next to a LM, with the CSM's nose pointed at the "front door" of the LM rather than at its top docking port. The CSM is trailing rocket fire in a circle. The crew's names are along the top edge of the circle, with APOLLO IX at the bottom. The "D" in McDivitt's name is filled with red to mark that this was the "Dmission" in the alphabetic sequence of Apollo missions. The patch was designed by Allen Stevens of Rockwell International.

Planning and training

Apollo 9's main purpose was to qualify the LM for crewed lunar flight, demonstrating, among other things, that it could perform the maneuvers in space that would be needed for a lunar landing, including docking with the CSM. Colin Burgess and Francis French, in their book about the Apollo Program, deemed McDivitt's crew among the best trained ever—they had worked together since January 1966, at first as backups for Apollo 1, and they always had the assignment of being the first to fly the LM. Flight Director Gene Kranz deemed the Apollo9 crew the best prepared for their mission, and felt Scott was an extremely knowledgeable CMP. Crew members underwent some 1,800 hours of mission-specific training, about seven hours for every hour they would spend in flight. Their training even started on the day before the Apollo1 fire, in the very first Block II spacecraft in which they were originally intended to fly. They took part in the vehicle checkouts for the CSM at North American Rockwell's facility in Downey, California, and for the LM at Grumman's plant in Bethpage, New York. They also participated in testing of the modules at the launch site.

Among the types of the training which the crew underwent were simulations of zero-G, both underwater and in the Vomit Comet. During these exercises, they practiced for the planned extravehicular activities (EVAs). They traveled to Cambridge, Massachusetts, for training on the Apollo Guidance Computer (AGC) at MIT. The crew studied the sky at the Morehead Planetarium and at the Griffith Planetarium, especially focusing on the 37 stars used by the AGC. They each spent more than 300 hours in the CM and LM simulators at Kennedy Space Center (KSC) and at Houston, some involving live participation by Mission Control. Additional time was spent in simulators in other locations.

The first mission to use the CSM, the LM and a SaturnV, Apollo9 allowed the launch preparations team at KSC its first opportunity to simulate the launch of a lunar landing mission. The LM arrived from Grumman in June 1968 and was subjected to extensive testing including in the altitude chamber, simulating space conditions. As this occurred, other technicians assembled the SaturnV inside the Vehicle Assembly Building (VAB). The CM and SM arrived in October, but even the experienced KSC team from North American had trouble joining them together. When the lander was done with the altitude chamber, the CSM took its place, letting the LM be available for installation of equipment such as rendezvous radar and antennas. There were no lengthy delays, and on January 3, 1969, the launch vehicle was taken out of the VAB and moved to Launch Complex 39A by crawler. Flight readiness reviews for the CM, the LM, and the SaturnV were held and passed in the following weeks.

Launch vehicle
The Saturn V (AS-504) used on Apollo9 was the fourth to be flown, the second to carry astronauts to space, and the first to bear a lunar module. Although similar in configuration to the SaturnV used on Apollo 8, several changes were made. The inner core of the F-1 engine chamber in the first (S-IC) stage was removed, thus saving weight and allowing for a slight increase in specific impulse. Weight was also saved by replacing the skins of the liquid oxygen tanks with lighter ones, and by providing lighter versions of other components. Efficiency was increased in the S-II second stage with uprated J-2 engines, and through a closed-loop propellant utilization system rather than Apollo 8's open-loop system. Of the 3250 lb weight reduction in the second stage, about half came from a 16 percent reduction in the thickness of the tank side walls.

Spacecraft, equipment and call signs

Apollo9 used CSM-104, the third Block II CSM to be flown with astronauts aboard. Apollo 8, lacking a lunar module, did not have docking equipment; Apollo9 flew the probe-and-drogue assembly used for docking along with other equipment added near the forward hatch of the CM; this allowed for rigid docking of the two craft, and for internal transfer between CM and LM. Had the switch in missions between Apollo8 and9 not occurred, the Earth-orbit mission would have flown CSM-103, which flew on Apollo 8.

The Earth-orbit mission was originally supposed to use LM-2 as its lunar module, but the crew found numerous flaws in it, many associated with it being the first flight-ready lunar module off Grumman's production line. The delay occasioned by the switch in missions allowed LM-3 to be available, a machine the crew found far superior. Neither LM-2 nor LM-3 could have been sent to the Moon as both were too heavy; Grumman's weight reduction program for the LMs only became fully effective with LM-5, designated for Apollo 11. Small cracks in LM-3's aluminum alloy structure due to stresses such as the insertion of a rivet proved an ongoing issue; Grumman's engineers continued working to fix them until the LM had to be mounted on the SaturnV in December 1968, where it was housed inside the Spacecraft-Lunar Module Adapter, numbered as SLA-11A. LM-2 never flew in space and is in the National Air and Space Museum.

The Apollo astronauts were provided with early versions of the Sony Walkman, portable cassette recorders intended to allow them to make observations during the mission. The Apollo9 crew was the first to be allowed to bring music mixtapes, one each, that could be played in that device. McDivitt and Scott preferred easy listening and country music; Schweickart's cassette tape of classical music went missing until the ninth day of the ten-day mission, when it was presented to him by Scott.

After the Gemini 3 craft was dubbed Molly Brown by Grissom, NASA forbade naming spacecraft. The fact that during the Apollo9 mission, the CSM and LM would separate and need different call signs caused the Apollo9 astronauts to push for a change. In simulations, they began to refer to the CSM as "Gumdrop", a name inspired by the CM's appearance while in the blue protective wrapping in which it was transported from the manufacturer, and the LM as "Spider", inspired by the LM's appearance with landing legs deployed. Personnel in NASA public relations thought the names were too informal, but the call signs ultimately gained official sanction. NASA required more formal call signs for future missions, starting with Apollo 11.

Life Support System backpack

The Extravehicular Mobility Unit (EMU) backpack flew for the first time on Apollo9, used by Schweickart during his EVA. This included the Portable Life Support System (PLSS), providing oxygen to the astronaut and water for the Liquid Cooling Garment (LCG), which helped prevent overheating during extravehicular activity. Also present was the Oxygen Purge System (OPS), the "bedroll" atop the backpack, which could provide oxygen for up to roughly an hour if the PLSS failed. A more advanced version of the EMU was used for the lunar landing on Apollo 11.

During his stand-up EVA, Scott did not wear a PLSS, but was connected to the CM's life support systems through an umbilical, utilizing a Pressure Control Valve (PCV). This device had been created in 1967 to allow for stand-up EVAs from the hatches of the LM or CM, or for brief ventures outside. It was later used by Scott for his lunar surface stand-up EVA on Apollo 15, and for the deep-space EVAs by the command module pilots of the final three Apollo flights.

First through fifth days (March 3–7)

Originally scheduled to launch on February 28, 1969, the liftoff of Apollo9 was postponed because all three astronauts had colds, and NASA did not want to risk that the mission might be affected. Around-the-clock labor shifts were required to keep the spacecraft in readiness; the delay cost $500,000. The rocket launched from KSC at 11:00:00 EST (16:00:00 GMT) on March 3. This was well within the launch window, which would have remained open for another three and a quarter hours. Present in the firing control room was Vice President Spiro Agnew on behalf of the new Nixon administration.

McDivitt reported a smooth ride during the launch, although there was some vibration and the astronauts were surprised to be pushed forward when the Saturn V's first stage stopped firing, before its second stage took over, when they were pushed back into their couches. Each of the first two stages slightly underperformed; a deficiency made up, more or less, by the S-IVB third stage. Once the third stage cut out at 00:11:04.7 into the mission, Apollo9 had entered a parking orbit of 102.3 by.

The crew began their first major orbital task with the separation of the CSM from the S-IVB at 02:41:16 into the mission, seeking to turn around and then dock with the LM, which was on the end of the S-IVB, after which the combined spacecraft would separate from the rocket. If it was not possible to make such a docking, the lunar landing could not take place. It was Scott's responsibility to fly the CSM, which he did to a successful docking, as the probe-and-drogue docking assembly worked properly. After McDivitt and Schweickart inspected the tunnel connecting the CM and LM, the assembled spacecraft separated from the S-IVB. The next task was to demonstrate that two docked spacecraft could be maneuvered by one engine. The five-second burn took place at 05:59.01.1 into the mission, accomplished with the SM's Service Propulsion System (SPS), after which Scott excitedly reported the LM was still in place. Thereafter, the S-IVB was fired again, and the stage was sent into solar orbit.

From 09:00:00 to 19:30:00, a sleep period was scheduled. The astronauts slept well, but complained of being woken by non-English transmissions. Scott theorized that they were possibly in Chinese. The highlight of the second day in orbit (March 4) was three SPS burns. The initial burn, at 22:12:04.1, lasted 110 seconds, and including swiveling or "gimbaling" the engine to test whether the autopilot could dampen the induced oscillations, which it did within five seconds. Two more SPS burns followed, lightening the SM's fuel load. The spacecraft and engine passed every test, sometimes proving more robust than expected. The performance of the CSM in remaining stable while the engine was being gimbaled would in 1972 help cause McDivitt, by then manager of the Apollo Spacecraft Program, to approve the continuation of Apollo 16 when its CSM was experiencing an unstable gimbal after separation from its LM in lunar orbit.

The flight plan for the third day in space was to have the commander and lunar module pilot enter the LM to check out its systems and use its descent engine to move the entire spacecraft. The descent engine was the backup to the SPS; the ability to use it in this manner would prove critical on Apollo 13. The flight plan was thrown into question when Schweickart, suffering from space adaptation sickness, vomited, while McDivitt felt queasy as well. They had been avoiding sudden physical motions, but the contortion-like maneuvers to don their space suits for the LM checkout caused them to feel ill. The experience would teach the doctors enough about the sickness to have the astronauts avoid it on the lunar landings, but at the time Schweickart feared his vomiting might endanger Kennedy's goal. They were well enough to continue with the day's plan, and entered the LM, thus transferring between vehicles for the first time in the US space program, and making the first ever transfer without needing to spacewalk, as Soviet cosmonauts had. The hatches were then closed, though the modules remained docked, showing that Spider communications and life support systems would work in isolation from those of Gumdrop. On command, the landing legs sprang into the position they would assume for landing on the Moon.

In the LM, Schweickart vomited again, causing McDivitt to request a private channel to the doctors in Houston. The first episode had not been reported to the ground because of its brief nature, and when the media learned what had happened to Schweickart, there were "repercussions and a spate of unfriendly stories". They finished the LM checkout, including the successful firing of the descent engine, and returned to Scott in Gumdrop. The burn lasted 367 seconds and simulated the throttle pattern to be used during the landing on the Moon. After they returned, a fifth firing of the SPS was made, designed to circularize Apollo9's orbit in preparation for the rendezvous. This took place at 54:26:12.3, raising the craft's orbit to 142 by.

The fourth day's program (March 6) was for Schweickart to exit the hatch on the LM and make his way along the outside of the spacecraft to the CM's hatch, where Scott would stand by to assist, demonstrating that this could be done in the event of an emergency. Schweickart was to wear the life support backpack, or PLSS, to be worn on the lunar surface EVAs. This was the only EVA scheduled before the lunar landing, and thus the only opportunity to test the PLSS in space. McDivitt initially canceled the EVA due to Schweickart's condition, but with the lunar module pilot feeling better, decided to allow him to exit the LM, and once he was there, to move around the LM's exterior using handholds. Scott stood in the CM's hatch; both men photographed each other and retrieved experiments from the exterior of their vehicles. Schweickart found moving around easier than it had been in simulations; both he and Scott were confident that Schweickart could have completed the exterior transfer if called upon to do so, but considered it unnecessary. During the EVA, Schweickart used the call sign "Red Rover", a nod to the color of his hair.

On March 7, the fifth day, came "the key event of the entire mission: the separation and rendezvous of the lunar module and the command module". The lunar module lacked the capability to return the astronauts to Earth; this was the first time space travelers had flown in a vehicle that could not take them home. McDivitt and Schweickart entered the LM early, having obtained permission to do so without wearing their helmets and gloves, making it easier to set up the LM. When Scott in Gumdrop pushed the button to release the LM, it initially hung on the latches at the end of the docking probe, but he hit the button again and Spider was released. After spending about 45 minutes near Gumdrop, Spider went into a slightly higher orbit, meaning that over time, the two craft would separate, with Gumdrop ahead. Over the next hours, McDivitt fired the LM's descent engine at several throttle settings; by the end of the day the LM was thoroughly test-flown. At a distance of 185 km, Spider fired to lower its orbit and thus begin to catch up with Gumdrop, a process that would take over two hours, and the descent stage was jettisoned.

The approach and rendezvous were conducted as near as possible to what was planned for the lunar missions. To demonstrate that rendezvous could be performed by either craft, Spider was the active party during the maneuver. McDivitt brought Spider close to Gumdrop, then maneuvered the LM to show each side to Scott, allowing him to inspect for any damage. Then, McDivitt docked the craft. Due to glare from the Sun, he had trouble doing this and Scott guided him in. During the later missions, the job of docking the two spacecraft in lunar orbit would fall to the command module pilot. After McDivitt and Schweickart returned to Gumdrop, Spider was jettisoned, its engine fired to fuel depletion remotely by Mission Control as part of further testing of the engine, simulating an ascent stage's climb from the lunar surface. This raised Spider to an orbit with apogee of over 3700 nmi. The only major lunar module system not fully tested was the landing radar, as this could not be done in Earth orbit.

Sixth through eleventh days (March 8–13)

Apollo 9 was to remain in space for about ten days to check how the CSM would perform over the period of time required for a lunar mission. Most major events had been scheduled for the first days so that they would be accomplished if the flight needed to be ended early. The remaining days in orbit were to be conducted at a more leisurely pace. With the main goals of the mission accomplished, the hatch window was used for special photography of Earth, using four identical Hasselblad cameras, coupled together and using film sensitive to different parts of the electromagnetic spectrum. Such photography allowed different features of the Earth's surface to appear, for example, tracking of water pollution as it exits mouths of rivers into the sea, and the highlighting of agricultural areas using infrared. The camera system was a prototype, and would pave the way for the Earth Resources Technology Satellite, predecessor to the Landsat series. The photography was successful, as the ample time in orbit meant the crew could wait to allow cloud cover to pass, and would inform Skylab's mission planning.

Scott used a sextant to track landmarks on the Earth, and turned the instrument to the skies to observe the planet Jupiter, practicing navigation techniques that were to be used on later missions. The crew was able to track the Pegasus 3 satellite (launched in 1965) as well as the ascent stage of Spider. The sixth burn of the SPS engine took place on the sixth day, though it was postponed one orbit as the reaction control system (RCS) thruster burn needed to settle the reactants in their tanks was not properly programmed. The SPS burn lowered the perigee of Apollo9's orbit, allowing for improved RCS thruster deorbit capability as a backup to the SPS.

Considerable testing of the CSM took place, but this was principally Scott's responsibility, allowing McDivitt and Schweickart leisure to observe the Earth; they alerted Scott if anything particularly noteworthy was upcoming, letting him leave his work for a moment to look at Earth too. The seventh burn of the SPS system took place on the eighth day, March 10; its purpose was again to aid RCS deorbit capability, as well as extending Gumdrop orbital lifetime. It shifted the apogee of the orbit to the Southern Hemisphere, allowing for a longer free-fall time to entry when Apollo9 returned to Earth. The burn was extended to allow for testing of the propellent gaging system, which had been behaving anomalously during earlier SPS burns. Once it was accomplished, Apollo9's RCS thrusters could have returned it to Earth and still allowed it to land in the primary recovery zone had the SPS engine failed. The eighth and final SPS burn, to return the vehicle to Earth, was accomplished on March 13, less than an hour after the ten-day mark of the mission, after which the service module was jettisoned. The landing was delayed one orbit because of unfavorable weather in the primary landing zone some 220 nmi ESE of Bermuda. Instead, Apollo9 splashed down 160 nmi east of the Bahamas, about 3 mi from the recovery carrier, the USS Guadalcanal, after a mission lasting 10 days, 1hour, 54 seconds. Apollo9 was the last spacecraft to splash down in the Atlantic Ocean for a half century, until the Crew Dragon Demo-1 mission in 2019, and last crewed splashdown in the Atlantic until Inspiration4 in 2021.

Hardware disposition

The Apollo9 Command Module Gumdrop (1969-018A) is on display at the San Diego Air & Space Museum. Gumdrop was formerly displayed at the Michigan Space and Science Center, Jackson, Michigan, until April 2004, when the center closed. The service module, jettisoned shortly after the deorbit burn, reentered the atmosphere and disintegrated.

The ascent stage of LM-3 Spider (1969-018C) reentered on October 23, 1981. The descent stage of LM-3 Spider (1969-018D) reentered on March 22, 1969, landing in the Indian Ocean near North Africa. The S-IVB (1969-018B) was sent into solar orbit, with initial aphelion of 80093617 mi, perihelion of 44832845 mi and orbital period of 245 days. It remains in solar orbit.

Appraisal and aftermath
As NASA Associate Administrator George Mueller put it, "Apollo9 was as successful a flight as any of us could ever wish for, as well as being as successful as any of us have ever seen." Gene Kranz called Apollo9 "sheer exhilaration". Apollo Program Director Samuel C. Phillips stated, "in every way, it has exceeded even our most optimistic expectations." Apollo11 astronaut Buzz Aldrin stood in Mission Control as Spider and Gumdrop docked after their separate flights, and with the docking, according to Andrew Chaikin, "Apollo9 had fulfilled all its major objectives. At that moment, Aldrin knew Apollo10 would also succeed, and that he and Armstrong would attempt to land on the Moon. On March 24, NASA made it official."

Although he might have been offered command of an Apollo lunar landing mission, McDivitt chose to leave the Astronaut Corps after Apollo9, becoming manager of the Apollo Spacecraft Program later in 1969. Scott was soon given another spaceflight assignment as backup commander of Apollo 12, and then was made mission commander of Apollo 15, landing on the Moon in 1971. Schweickart volunteered for medical investigation of his spacesickness, but was unable to shake its stigma, and was never again assigned to a prime crew. He took a leave of absence from NASA in 1977 that eventually became permanent. Eugene Cernan, commander of Apollo 17, stated that when it came to understanding spacesickness, Schweickart "paid the price for them all".

Following the success of Apollo 9, NASA did not conduct the "E mission" (further testing in medium Earth orbit), and even considered skipping the "F mission", the dress rehearsal for the lunar landing, going straight to the landing attempt. As the spacecraft designated for the first landing attempt were still being assembled, this was not done. NASA officials also felt that given the past difficulties with the LM, there was a need for a further test flight before the actual landing attempt, and that orbiting the Moon would give them the opportunity to study mass concentrations there, which had affected Apollo8's orbit. According to French and Burgess in their study of the Apollo program, "Apollo9's success had ensured that the next Apollo mission would go back to the moon."

title: Apollo 9


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Arthritis

Arthritis is a term often used to mean any disorder that affects joints. Symptoms generally include joint pain and stiffness. Other symptoms may include redness, warmth, swelling, and decreased range of motion of the affected joints. In some types of arthritis, other organs are also affected. Onset can be gradual or sudden.

There are over 100 types of arthritis. The most common forms are osteoarthritis (degenerative joint disease) and rheumatoid arthritis. Osteoarthritis usually occurs with age and affects the fingers, knees, and hips. Rheumatoid arthritis is an autoimmune disorder that often affects the hands and feet. Other types include gout, lupus, fibromyalgia, and septic arthritis. They are all types of rheumatic disease.

Treatment may include resting the joint and alternating between applying ice and heat. Weight loss and exercise may also be useful. Recommended medications may depend on the form of arthritis. These may include pain medications such as ibuprofen and paracetamol (acetaminophen). In some circumstances, a joint replacement may be useful.

Osteoarthritis affects more than 3.8% of people, while rheumatoid arthritis affects about 0.24% of people. Gout affects about 1–2% of the Western population at some point in their lives. In Australia about 15% of people are affected by arthritis, while in the United States more than 20% have a type of arthritis. Overall the disease becomes more common with age. Arthritis is a common reason that people miss work and can result in a decreased quality of life. The term is derived from arthr- (meaning 'joint') and -itis (meaning 'inflammation').

Classification
There are several diseases where joint pain is primary, and is considered the main feature. Generally when a person has "arthritis" it means that they have one of these diseases, which include:
 * Hemarthrosis
 * Osteoarthritis
 * Rheumatoid arthritis
 * Gout and pseudo-gout
 * Septic arthritis
 * Ankylosing spondylitis
 * Juvenile idiopathic arthritis
 * Still's disease
 * Psoriatic arthritis

Joint pain can also be a symptom of other diseases. In this case, the arthritis is considered to be secondary to the main disease; these include:
 * Psoriasis
 * Reactive arthritis
 * Ehlers–Danlos syndrome
 * Iron overload
 * Hepatitis
 * Lyme disease
 * Sjögren's disease
 * Hashimoto's thyroiditis
 * Celiac disease
 * Non-celiac gluten sensitivity
 * Inflammatory bowel disease (including Crohn's disease and ulcerative colitis)
 * Henoch–Schönlein purpura
 * Hyperimmunoglobulinemia D with recurrent fever
 * Sarcoidosis
 * Whipple's disease
 * TNF receptor associated periodic syndrome
 * Granulomatosis with polyangiitis (and many other vasculitis syndromes)
 * Familial Mediterranean fever
 * Systemic lupus erythematosus

An undifferentiated arthritis is an arthritis that does not fit into well-known clinical disease categories, possibly being an early stage of a definite rheumatic disease.

Signs and symptoms
Pain, which can vary in severity, is a common symptom in virtually all types of arthritis. Other symptoms include swelling, joint stiffness, redness, and aching around the joint(s). Arthritic disorders like lupus and rheumatoid arthritis can affect other organs in the body, leading to a variety of symptoms. Symptoms may include:
 * Inability to use the hand or walk
 * Stiffness in one or more joints
 * Rash or itch
 * Malaise and fatigue
 * Weight loss
 * Poor sleep
 * Muscle aches and pains
 * Tenderness
 * Difficulty moving the joint

It is common in advanced arthritis for significant secondary changes to occur. For example, arthritic symptoms might make it difficult for a person to move around and/or exercise, which can lead to secondary effects, such as: These changes, in addition to the primary symptoms, can have a huge impact on quality of life.
 * Muscle weakness
 * Loss of flexibility
 * Decreased aerobic fitness

Disability
Arthritis is the most common cause of disability in the United States. More than 20 million individuals with arthritis have severe limitations in function on a daily basis. Absenteeism and frequent visits to the physician are common in individuals who have arthritis. Arthritis can make it difficult for individuals to be physically active and some become home bound. It is estimated that the total cost of arthritis cases is close to $100 billion of which almost 50% is from lost earnings. Each year, arthritis results in nearly 1 million hospitalizations and close to 45 million outpatient visits to health care centers.

Decreased mobility, in combination with the above symptoms, can make it difficult for an individual to remain physically active, contributing to an increased risk of obesity, high cholesterol or vulnerability to heart disease. People with arthritis are also at increased risk of depression, which may be a response to numerous factors, including fear of worsening symptoms.

Risk factors
There are common risk factors that increase a person's chance of developing arthritis later in adulthood. Some of these are modifiable while others are not. Smoking has been linked to an increased susceptibility of developing arthritis, particularly rheumatoid arthritis.

Diagnosis
Diagnosis is made by clinical examination from an appropriate health professional, and may be supported by other tests such as radiology and blood tests, depending on the type of suspected arthritis. All arthritides potentially feature pain. Pain patterns may differ depending on the arthritides and the location. Rheumatoid arthritis is generally worse in the morning and associated with stiffness lasting over 30 minutes.

Elements of the history of the disorder guide diagnosis. Important features are speed and time of onset, pattern of joint involvement, symmetry of symptoms, early morning stiffness, tenderness, gelling or locking with inactivity, aggravating and relieving factors, and other systemic symptoms. It may include checking joints, observing movements, examination of skin for rashes or nodules and symptoms of pulmonary inflammation. Physical examination may confirm the diagnosis or may indicate systemic disease. Radiographs are often used to follow progression or help assess severity.

Blood tests and X-rays of the affected joints often are performed to make the diagnosis. Screening blood tests are indicated if certain arthritides are suspected. These might include: rheumatoid factor, antinuclear factor (ANF), extractable nuclear antigen, and specific antibodies.

Rheumatoid arthritis patients often have high erythrocyte sedimentation rate (ESR, also known as sed rate) or C-reactive protein (CRP) levels, which indicates the presence of an inflammatory process in the body. Anti-cyclic citrullinated peptide (anti-CCP) antibodies and rheumatoid factor (RF) are two more common blood tests. Positive results indicate the risk of rheumatoid arthritis, while negative results help rule out this autoimmune condition.

Imaging tests like X-rays, MRI scans or Ultrasounds used to diagnose and monitor arthritis. Other imaging tests for rheumatoid arthritis that may be considered include computed tomography (CT) scanning, positron emission tomography (PET) scanning, bone scanning, and dual-energy X-ray absorptiometry (DEXA).

Osteoarthritis
Osteoarthritis is the most common form of arthritis. It affects humans and other animals, notably dogs, but also occurs in cats and horses. It can affect both the larger and the smaller joints of the body. In humans, this includes the hands, wrists, feet, back, hip, and knee. In dogs, this includes the elbow, hip, stifle (knee), shoulder, and back. The disease is essentially one acquired from daily wear and tear of the joint; however, osteoarthritis can also occur as a result of injury. Osteoarthritis begins in the cartilage and eventually causes the two opposing bones to erode into each other. The condition starts with minor pain during physical activity, but soon the pain can be continuous and even occur while in a state of rest. The pain can be debilitating and prevent one from doing some activities. In dogs, this pain can significantly affect quality of life and may include difficulty going up and down stairs, struggling to get up after lying down, trouble walking on slick floors, being unable to hop in and out of vehicles, difficulty jumping on and off furniture, and behavioral changes (e.g., aggression, difficulty squatting to toilet). Osteoarthritis typically affects the weight-bearing joints, such as the back, knee and hip. Unlike rheumatoid arthritis, osteoarthritis is most commonly a disease of the elderly. The strongest predictor of osteoarthritis is increased age, likely due to the declining ability of chondrocytes to maintain the structural integrity of cartilage. More than 30 percent of women have some degree of osteoarthritis by age 65. Other risk factors for osteoarthritis include prior joint trauma, obesity, and a sedentary lifestyle.

Rheumatoid arthritis
Rheumatoid arthritis (RA) is a disorder in which the body's own immune system starts to attack body tissues. The attack is not only directed at the joint but to many other parts of the body. In rheumatoid arthritis, most damage occurs to the joint lining and cartilage which eventually results in erosion of two opposing bones. RA often affects joints in the fingers, wrists, knees and elbows, is symmetrical (appears on both sides of the body), and can lead to severe deformity in a few years if not treated. RA occurs mostly in people aged 20 and above. In children, the disorder can present with a skin rash, fever, pain, disability, and limitations in daily activities. With earlier diagnosis and aggressive treatment, many individuals can lead a better quality of life than if going undiagnosed for long after RA's onset. The risk factors with the strongest association for developing rheumatoid arthritis are the female sex, a family history of rheumatoid arthritis, age, obesity, previous joint damage from an injury, and exposure to tobacco smoke.

Bone erosion is a central feature of rheumatoid arthritis. Bone continuously undergoes remodeling by actions of bone resorbing osteoclasts and bone forming osteoblasts. One of the main triggers of bone erosion in the joints in rheumatoid arthritis is inflammation of the synovium, caused in part by the production of pro-inflammatory cytokines and receptor activator of nuclear factor kappa B ligand (RANKL), a cell surface protein present in Th17 cells and osteoblasts. Osteoclast activity can be directly induced by osteoblasts through the RANK/RANKL mechanism.

Lupus
Lupus is a common collagen vascular disorder that can be present with severe arthritis. Other features of lupus include a skin rash, extreme photosensitivity, hair loss, kidney problems, lung fibrosis and constant joint pain.

Gout
Gout is caused by deposition of uric acid crystals in the joints, causing inflammation. There is also an uncommon form of gouty arthritis caused by the formation of rhomboid crystals of calcium pyrophosphate known as pseudogout. In the early stages, the gouty arthritis usually occurs in one joint, but with time, it can occur in many joints and be quite crippling. The joints in gout can often become swollen and lose function. Gouty arthritis can become particularly painful and potentially debilitating when gout cannot successfully be treated. When uric acid levels and gout symptoms cannot be controlled with standard gout medicines that decrease the production of uric acid (e.g., allopurinol) or increase uric acid elimination from the body through the kidneys (e.g., probenecid), this can be referred to as refractory chronic gout.

Other
Infectious arthritis is another severe form of arthritis. It presents with sudden onset of chills, fever and joint pain. The condition is caused by bacteria elsewhere in the body. Infectious arthritis must be rapidly diagnosed and treated promptly to prevent irreversible joint damage. Only about 1% of cases of infectious arthritis are due to any of a wide variety of viruses. The virus SARS-CoV-2, which causes Covid-19 has been added to the list of viruses which can cause infections arthritis. SARS-CoV-2 causes reactive arthritis.

Psoriasis can develop into psoriatic arthritis. With psoriatic arthritis, most individuals develop the skin problem first and then the arthritis. The typical features are continuous joint pains, stiffness and swelling. The disease does recur with periods of remission but there is no known cure for the disorder. A small percentage develop a severely painful and destructive form of arthritis which destroys the small joints in the hands and can lead to permanent disability and loss of hand function.

Treatment
There is no known cure for arthritis and rheumatic diseases. Treatment options vary depending on the type of arthritis and include physical therapy, exercise and diet, orthopedic bracing, and oral and topical medications. Joint replacement surgery may be required to repair damage, restore function, or relieve pain.

Physical therapy
In general, studies have shown that physical exercise of the affected joint can noticeably improve long-term pain relief. Furthermore, exercise of the arthritic joint is encouraged to maintain the health of the particular joint and the overall body of the person.

Individuals with arthritis can benefit from both physical and occupational therapy. In arthritis the joints become stiff and the range of movement can be limited. Physical therapy has been shown to significantly improve function, decrease pain, and delay the need for surgical intervention in advanced cases. Exercise prescribed by a physical therapist has been shown to be more effective than medications in treating osteoarthritis of the knee. Exercise often focuses on improving muscle strength, endurance and flexibility. In some cases, exercises may be designed to train balance. Occupational therapy can provide assistance with activities. Assistive technology is a tool used to aid a person's disability by reducing their physical barriers by improving the use of their damaged body part, typically after an amputation. Assistive technology devices can be customized to the patient or bought commercially.

Medications
There are several types of medications that are used for the treatment of arthritis. Treatment typically begins with medications that have the fewest side effects with further medications being added if insufficiently effective.

Depending on the type of arthritis, the medications that are given may be different. For example, the first-line treatment for osteoarthritis is acetaminophen (paracetamol) while for inflammatory arthritis it involves non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen. Opioids and NSAIDs may be less well tolerated. However, topical NSAIDs may have better safety profiles than oral NSAIDs. For more severe cases of osteoarthritis, intra-articular corticosteroid injections may also be considered.

The drugs to treat rheumatoid arthritis (RA) range from corticosteroids to monoclonal antibodies given intravenously. Due to the autoimmune nature of RA, treatments may include not only pain medications and anti-inflammatory drugs, but also another category of drugs called disease-modifying antirheumatic drugs (DMARDs). csDMARDs, TNF biologics and tsDMARDs are specific kinds of DMARDs that are recommended for treatment. Treatment with DMARDs is designed to slow down the progression of RA by initiating an adaptive immune response, in part by CD4+ T helper (Th) cells, specifically Th17 cells. Th17 cells are present in higher quantities at the site of bone destruction in joints and produce inflammatory cytokines associated with inflammation, such as interleukin-17 (IL-17).

Surgery
A number of rheumasurgical interventions have been incorporated in the treatment of arthritis since the 1950s. Arthroscopic surgery for osteoarthritis of the knee provides no additional benefit to optimized physical and medical therapy.

Adaptive aids
People with hand arthritis can have trouble with simple activities of daily living tasks (ADLs), such as turning a key in a lock or opening jars, as these activities can be cumbersome and painful. There are adaptive aids or assistive devices (ADs) available to help with these tasks, but they are generally more costly than conventional products with the same function. It is now possible to 3-D print adaptive aids, which have been released as open source hardware to reduce patient costs. Adaptive aids can significantly help arthritis patients and the vast majority of those with arthritis need and use them.

Alternative medicine
Further research is required to determine if transcutaneous electrical nerve stimulation (TENS) for knee osteoarthritis is effective for controlling pain.

Low level laser therapy may be considered for relief of pain and stiffness associated with arthritis. Evidence of benefit is tentative.

Pulsed electromagnetic field therapy (PEMFT) has tentative evidence supporting improved functioning but no evidence of improved pain in osteoarthritis. The FDA has not approved PEMFT for the treatment of arthritis. In Canada, PEMF devices are legally licensed by Health Canada for the treatment of pain associated with arthritic conditions.

Epidemiology
Arthritis is predominantly a disease of the elderly, but children can also be affected by the disease. Arthritis is more common in women than men at all ages and affects all races, ethnic groups and cultures. In the United States a CDC survey based on data from 2013 to 2015 showed 54.4 million (22.7%) adults had self-reported doctor-diagnosed arthritis, and 23.7 million (43.5% of those with arthritis) had arthritis-attributable activity limitation (AAAL). With an aging population, this number is expected to increase. Adults with co-morbid conditions, such as heart disease, diabetes, and obesity, were seen to have a higher than average prevalence of doctor-diagnosed arthritis (49.3%, 47.1%, and 30.6% respectively).

Disability due to musculoskeletal disorders increased by 45% from 1990 to 2010. Of these, osteoarthritis is the fastest increasing major health condition. Among the many reports on the increased prevalence of musculoskeletal conditions, data from Africa are lacking and underestimated. A systematic review assessed the prevalence of arthritis in Africa and included twenty population-based and seven hospital-based studies. The majority of studies, twelve, were from South Africa. Nine studies were well-conducted, eleven studies were of moderate quality, and seven studies were conducted poorly. The results of the systematic review were as follows:
 * Rheumatoid arthritis: 0.1% in Algeria (urban setting); 0.6% in Democratic Republic of Congo (urban setting); 2.5% and 0.07% in urban and rural settings in South Africa respectively; 0.3% in Egypt (rural setting), 0.4% in Lesotho (rural setting)
 * Osteoarthritis: 55.1% in South Africa (urban setting); ranged from 29.5 to 82.7% in South Africans aged 65 years and older
 * Knee osteoarthritis has the highest prevalence from all types of osteoarthritis, with 33.1% in rural South Africa
 * Ankylosing spondylitis: 0.1% in South Africa (rural setting)
 * Psoriatic arthritis: 4.4% in South Africa (urban setting)
 * Gout: 0.7% in South Africa (urban setting)
 * Juvenile idiopathic arthritis: 0.3% in Egypt (urban setting)

History
Evidence of osteoarthritis and potentially inflammatory arthritis has been discovered in dinosaurs. The first known traces of human arthritis date back as far as 4500 BC. In early reports, arthritis was frequently referred to as the most common ailment of prehistoric peoples. It was noted in skeletal remains of Native Americans found in Tennessee and parts of what is now Olathe, Kansas. Evidence of arthritis has been found throughout history, from Ötzi, a mummy (c. 3000 BC) found along the border of modern Italy and Austria, to the Egyptian mummies c. 2590 BC.

In 1715, William Musgrave published the second edition of his most important medical work, De arthritide symptomatica, which concerned arthritis and its effects. Augustin Jacob Landré-Beauvais, a 28-year-old resident physician at Salpêtrière Asylum in France was the first person to describe the symptoms of rheumatoid arthritis. Though Landré-Beauvais' classification of rheumatoid arthritis as a relative of gout was inaccurate, his dissertation encouraged others to further study the disease.

Terminology
The term is derived from arthr- (from ἄρθρον) and -itis (from -ῖτις,, lit. 'pertaining to'), the latter suffix having come to be associated with inflammation.

The word arthritides is the plural form of arthritis, and denotes the collective group of arthritis-like conditions.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Arthritis


text:
April 2

Pre-1600

 * 1513 – Having spotted land on March 27, Spanish explorer Juan Ponce de León comes ashore on what is now the U.S. state of Florida, landing somewhere between the modern city of St. Augustine and the mouth of the St. Johns River.

1601–1900

 * 1755 – Commodore William James captures the Maratha fortress of Suvarnadurg on the west coast of India.
 * 1792 – The Coinage Act is passed by Congress, establishing the United States Mint.
 * 1800 – Ludwig van Beethoven leads the premiere of his First Symphony in Vienna.
 * 1801 – French Revolutionary Wars: In the Battle of Copenhagen a British Royal Navy squadron defeats a hastily assembled, smaller, mostly-volunteer Dano-Norwegian Navy at high cost, forcing Denmark out of the Second League of Armed Neutrality.
 * 1863 – American Civil War: The largest in a series of Southern bread riots occurs in Richmond, Virginia.
 * 1865 – American Civil War: Defeat at the Third Battle of Petersburg forces the Army of Northern Virginia and the Confederate government to abandon Richmond, Virginia.
 * 1885 – Canadian Cree warriors attack the village of Frog Lake, killing nine.

1901–present

 * 1902 – Dmitry Sipyagin, Minister of Interior of the Russian Empire, is assassinated in the Mariinsky Palace, Saint Petersburg.
 * 1902  – "Electric Theatre", the first full-time movie theater in the United States, opens in Los Angeles.
 * 1911 – The Australian Bureau of Statistics conducts the country's first national census.
 * 1912 – The ill-fated RMS Titanic begins sea trials.
 * 1917 – American entry into World War I: President Wilson asks the U.S. Congress for a declaration of war on Germany.
 * 1921 – The Autonomous Government of Khorasan, a military government encompassing the modern state of Iran, is established.
 * 1930 – After the mysterious death of Empress Zewditu, Haile Selassie is proclaimed emperor of Ethiopia.
 * 1954 – A 19-month-old infant is swept up in the ocean tides at Hermosa Beach, California. Local photographer John L. Gaunt photographs the incident; 1955 Pulitzer winner "Tragedy by the Sea".
 * 1956 – As the World Turns and The Edge of Night premiere on CBS. The two soaps become the first daytime dramas to debut in the 30-minute format.
 * 1964 – The Soviet Union launches Zond 1.
 * 1969 – LOT Polish Airlines Flight 165 crashes into the Polica mountain near Zawoja, Poland, killing 53.
 * 1972 – Actor Charlie Chaplin returns to the United States for the first time since being labeled a communist during the Red Scare in the early 1950s.
 * 1973 – Launch of the LexisNexis computerized legal research service.
 * 1975 – Vietnam War: Thousands of civilian refugees flee from Quảng Ngãi Province in front of advancing North Vietnamese troops.
 * 1976 – Prince Norodom Sihanouk resigns as leader of Cambodia and is placed under house arrest.
 * 1979 – A Soviet bio-warfare laboratory at Sverdlovsk accidentally releases airborne anthrax spores, killing 66 plus an unknown amount of livestock.
 * 1980 – United States President Jimmy Carter signs the Crude Oil Windfall Profits Tax Act.
 * 1982 – Falklands War: Argentina invades the Falkland Islands.
 * 1986 – Alabama governor George Wallace, a former segregationist, best known for the "Stand in the Schoolhouse Door", announces that he will not seek a fifth four-year term and will retire from public life upon the end of his term in January 1987.
 * 1989 – Soviet leader Mikhail Gorbachev arrives in Havana, Cuba, to meet with Fidel Castro in an attempt to mend strained relations.
 * 1991 – Rita Johnston becomes the first female Premier of a Canadian province when she succeeds William Vander Zalm (who had resigned) as Premier of British Columbia.
 * 1992 – In New York, Mafia boss John Gotti is convicted of murder and racketeering and is later sentenced to life in prison.
 * 1992  – Forty-two civilians are massacred in the town of Bijeljina in Bosnia and Herzegovina.
 * 2002 – Israeli forces surround the Church of the Nativity in Bethlehem, into which armed Palestinians had retreated.
 * 2004 – Islamist terrorists involved in the 11 March 2004 Madrid attacks attempt to bomb the Spanish high-speed train AVE near Madrid; the attack is thwarted.
 * 2006 – Over 60 tornadoes break out in the United States; Tennessee is hardest hit with 29 people killed.
 * 2011 – India wins the Cricket World Cup for the second time in history under the captaincy of MS Dhoni.
 * 2012 – A mass shooting at Oikos University in California leaves seven people dead and three injured.
 * 2012  – UTair Flight 120 crashes after takeoff from Roshchino International Airport in Tyumen, Russia, killing 33 and injuring 10.
 * 2014 – A spree shooting occurs at the Fort Hood army base in Texas, with four dead, including the gunman, and 16 others injured.
 * 2015 – Gunmen attack Garissa University College in Kenya, killing at least 148 people and wounding 79 others.
 * 2015  – Four men steal items worth up to £200 million from an underground safe deposit facility in London's Hatton Garden area in what has been called the "largest burglary in English legal history."
 * 2020 – COVID-19 pandemic: The total number of confirmed cases reach one million.
 * 2021 – At least 49 people are killed in a train derailment in Taiwan after a truck accidentally rolls onto the track.
 * 2021  – A Capitol Police officer is killed and another injured when an attacker rams his car into a barricade outside the United States Capitol.
 * 2024 – Viertola school shooting: A 12-year-old pupil is killed and two others injured by a shooter of the same age in Vantaa, Finland.

Pre-1600

 * 181 – Emperor Xian of Han, Chinese emperor (d. 234)
 * 747 – Charlemagne, Frankish king (d. 814)
 * 1473 – John Corvinus, Hungarian noble (d. 1504)
 * 1545 – Elisabeth of Valois (d. 1568)
 * 1565 – Cornelis de Houtman, Dutch explorer (d. 1599)
 * 1586 – Pietro Della Valle, Italian traveler (d. 1652)

1601–1900

 * 1602 – Mary of Jesus of Ágreda, Franciscan abbess (d. 1665)
 * 1618 – Francesco Maria Grimaldi, Italian mathematician and physicist (d. 1663)
 * 1647 – Maria Sibylla Merian, German-Dutch botanist and illustrator (d. 1717)
 * 1653 – Prince George of Denmark (d. 1708)
 * 1696 – Francesca Cuzzoni, Italian operatic soprano (d. 1778)
 * 1719 – Johann Wilhelm Ludwig Gleim, German poet (d. 1803)
 * 1725 – Giacomo Casanova, Italian explorer and author (d. 1798)
 * 1755 – Jean Anthelme Brillat-Savarin, French lawyer and politician (d. 1826)
 * 1788 – Francisco Balagtas, Filipino poet and author (d. 1862)
 * 1788  – Wilhelmine Reichard, German balloonist (d. 1848)
 * 1789 – Lucio Norberto Mansilla, Argentinian general and politician (d. 1871)
 * 1792 – Francisco de Paula Santander, Colombian general and politician, 4th President of the Republic of the New Granada (d. 1840)
 * 1798 – August Heinrich Hoffmann von Fallersleben, German poet and academic (d. 1874)
 * 1805 – Hans Christian Andersen, Danish novelist, short story writer, and poet (d. 1875)
 * 1814 – Henry L. Benning, American general and judge (d. 1875)
 * 1814  – Erastus Brigham Bigelow, American inventor (d. 1879)
 * 1827 – William Holman Hunt, English soldier and painter (d. 1910)
 * 1835 – Jacob Nash Victor, American engineer (d. 1907)
 * 1838 – Léon Gambetta, French lawyer and politician, 45th Prime Minister of France (d. 1882)
 * 1840 – Émile Zola, French novelist, playwright, journalist (d. 1902)
 * 1841 – Clément Ader, French engineer, designed the Ader Avion III (d. 1926)
 * 1842 – Dominic Savio, Italian Catholic saint, adolescent student of Saint John Bosco (d. 1857)
 * 1861 – Iván Persa, Slovenian priest and author (d. 1935)
 * 1862 – Nicholas Murray Butler, American philosopher and academic, Nobel Prize laureate (d. 1947)
 * 1869 – Hughie Jennings, American baseball player and manager (d. 1928)
 * 1870 – Edmund Dwyer-Gray, Irish-Australian politician, 29th Premier of Tasmania (d. 1945)
 * 1875 – Walter Chrysler, American businessman, founded Chrysler (d. 1940)
 * 1875  – William Donne, English cricketer and captain (d. 1942)
 * 1884 – J. C. Squire, English poet, author, and historian (d. 1958)
 * 1888 – Neville Cardus, English cricket and music writer (d. 1975)
 * 1891 – Jack Buchanan, Scottish entertainer (d. 1957)
 * 1891  – Max Ernst, German painter, sculptor, and poet (d. 1976)
 * 1891  – Tristão de Bragança Cunha, Indian nationalist and anti-colonial activist from Goa (d. 1958)
 * 1896 – Johnny Golden, American golfer (d. 1936)
 * 1898 – Harindranath Chattopadhyay, Indian poet, actor and politician (d. 1990)
 * 1898  – Chiungtze C. Tsen, Chinese mathematician (d. 1940)
 * 1900 – Roberto Arlt, Argentinian journalist, author, and playwright (d. 1942)
 * 1900  – Anis Fuleihan, Cypriot-American pianist, composer, and conductor (d. 1970)
 * 1900  – Alfred Strange, English footballer (d. 1978)

1901–present

 * 1902 – Jan Tschichold, German-Swiss graphic designer and typographer (d. 1974)
 * 1902  – Menachem Mendel Schneerson, the seventh Lubavitcher Rebbe (d. 1994)
 * 1903 – Lionel Chevrier, Canadian lawyer and politician, 27th Canadian Minister of Justice (d. 1987)
 * 1906 – Alphonse-Marie Parent, Canadian priest and educator (d. 1970)
 * 1907 – Harald Andersson, American-Swedish discus thrower (d. 1985)
 * 1907  – Luke Appling, American baseball player and manager (d. 1991)
 * 1908 – Buddy Ebsen, American actor and dancer (d. 2003)
 * 1910 – Paul Triquet, Canadian general, Victoria Cross recipient (d. 1980)
 * 1910  – Chico Xavier, Brazilian spiritual medium (d. 2002)
 * 1914 – Alec Guinness, English actor (d. 2000)
 * 1919 – Delfo Cabrera, Argentinian runner and soldier (d. 1981)
 * 1920 – Gerald Bouey, Canadian lieutenant and civil servant (d. 2004)
 * 1920  – Jack Stokes, English animator and director (d. 2013)
 * 1920  – Jack Webb, American actor, director, producer, and screenwriter (d. 1982)
 * 1922 – John C. Whitehead, American banker and politician, 9th United States Deputy Secretary of State (d. 2015)
 * 1923 – Gloria Henry, actress (d. 2021)
 * 1923  – Johnny Paton, Scottish footballer, coach, and manager (d. 2015)
 * 1923  – G. Spencer-Brown, English mathematician, psychologist, and author (d. 2016)
 * 1924 – Bobby Ávila, Mexican baseball player (d. 2004)
 * 1925 – George MacDonald Fraser, Scottish author and screenwriter (d. 2008)
 * 1925  – Hans Rosenthal, German radio and television host (d. 1987)
 * 1926 – Jack Brabham, Australian race car driver (d. 2014)
 * 1926  – Rudra Rajasingham, Sri Lankan police officer and diplomat (d. 2006)
 * 1927 – Carmen Basilio, American boxer and soldier (d. 2012)
 * 1927  – Howard Callaway, American soldier and politician, 11th United States Secretary of the Army (d. 2014)
 * 1927  – Rita Gam, American actress (d. 2016)
 * 1927  – Billy Pierce, American baseball player and sportscaster (d. 2015)
 * 1927  – Kenneth Tynan, English author and critic (d. 1980)
 * 1928 – Joseph Bernardin, American cardinal (d. 1996)
 * 1928  – Serge Gainsbourg, French singer-songwriter, actor, and director (d. 1991)
 * 1928  – Roy Masters, English-American radio host (d. 2021)
 * 1928  – David Robinson, Northern Irish horticulturist and academic (d. 2004)
 * 1929 – Ed Dorn, American poet and educator (d. 1999)
 * 1930 – Roddy Maude-Roxby, English actor
 * 1931 – Keith Hitchins, American historian (d. 2020)
 * 1931  – Vladimir Kuznetsov, Russian javelin thrower (d. 1986)
 * 1932 – Edward Egan, American cardinal (d. 2015)
 * 1933 – György Konrád, Hungarian sociologist and author (d. 2019)
 * 1934 – Paul Cohen, American mathematician and theorist (d. 2007)
 * 1934  – Brian Glover, English wrestler and actor (d. 1997)
 * 1934  – Carl Kasell, American journalist and game show host (d. 2018)
 * 1934  – Richard Portman, American sound engineer (d. 2017)
 * 1934  – Dovid Shmidel, Austrian-born Israeli rabbi
 * 1936 – Shaul Ladany, Serbian-Israeli race walker and engineer
 * 1937 – Dick Radatz, American baseball player (d. 2005)
 * 1938 – John Larsson, Swedish 17th General of The Salvation Army (d. 2022)
 * 1938  – Booker Little, American trumpet player and composer (d. 1961)
 * 1938  – Al Weis, American baseball player
 * 1939 – Marvin Gaye, American singer-songwriter (d. 1984)
 * 1939  – Anthony Lake, American academic and diplomat, 18th United States National Security Advisor
 * 1939  – Lise Thibault, Canadian journalist and politician, 27th Lieutenant Governor of Quebec
 * 1940 – Donald Jackson, Canadian figure skater and coach
 * 1940  – Mike Hailwood, English motorcycle racer (d. 1981)
 * 1940  – Penelope Keith, English actress
 * 1941 – Dr. Demento, American radio host
 * 1941  – Sonny Throckmorton, American country singer-songwriter
 * 1942 – Leon Russell, American singer-songwriter and pianist (d. 2016)
 * 1942  – Roshan Seth, Indian-English actor
 * 1943 – Michael Boyce, Baron Boyce, South African-English admiral and politician, Lord Warden of the Cinque Ports (d. 2022)
 * 1943  – Caterina Bueno, Italian singer (d. 2007)
 * 1943  – Larry Coryell, American jazz guitarist (d. 2017)
 * 1943  – Antonio Sabàto, Sr., Italian actor (d. 2021)
 * 1944 – Bill Malinchak, American football player
 * 1945 – Jürgen Drews, German singer-songwriter
 * 1945  – Guy Fréquelin, French race car driver
 * 1945  – Linda Hunt, American actress
 * 1945  – Reggie Smith, American baseball player and coach
 * 1945  – Don Sutton, American baseball player and sportscaster (d. 2021)
 * 1945  – Anne Waldman, American poet
 * 1946 – Richard Collinge, New Zealand cricketer
 * 1946  – David Heyes, English politician
 * 1946  – Sue Townsend, English author and playwright (d. 2014)
 * 1946  – Kurt Winter, Canadian guitarist and songwriter (d. 1997)
 * 1947 – Paquita la del Barrio, Mexican singer-songwriter
 * 1947  – Tua Forsström, Finnish writer
 * 1947  – Emmylou Harris, American singer-songwriter and guitarist
 * 1947  – Camille Paglia, American author and critic
 * 1948 – Roald Als, Danish author and illustrator
 * 1948  – Dimitris Mitropanos, Greek singer (d. 2012)
 * 1948  – Daniel Okrent, American journalist and author
 * 1948  – Joan D. Vinge, American author
 * 1949 – Paul Gambaccini, American-English radio and television host
 * 1949  – Bernd Müller, German footballer
 * 1949  – Pamela Reed, American actress
 * 1949  – David Robinson, American drummer
 * 1950 – Lynn Westmoreland, American politician
 * 1951 – Ayako Okamoto, Japanese golfer
 * 1952 – Lennart Fagerlund, Swedish cyclist
 * 1952  – Will Hoy, English race car driver (d. 2002)
 * 1952  – Leon Wilkeson, American bass player and songwriter  (d. 2001)
 * 1953 – Jim Allister, Northern Irish lawyer and politician
 * 1953  – Rosemary Bryant Mariner, 20th and 21st-century U.S. Navy aviator (d. 2019)
 * 1953  – Malika Oufkir, Moroccan Berber writer
 * 1953  – Debralee Scott, American actress (d. 2005)
 * 1953  – James Vance, American author and playwright (d. 2017)
 * 1954 – Gregory Abbott, American singer-songwriter and producer
 * 1954  – Donald Petrie, American actor and director
 * 1955 – Michael Stone, Northern Irish loyalist paramilitary
 * 1957 – Caroline Dean, English biologist and academic
 * 1957  – Hank Steinbrenner, American businessman (d. 2020)
 * 1958 – Stefano Bettarello, Italian rugby player
 * 1958  – Larry Drew, American basketball player and coach
 * 1959 – Gelindo Bordin, Italian runner
 * 1959  – David Frankel, American director, producer, and screenwriter
 * 1959  – Juha Kankkunen, Finnish race car driver
 * 1959  – Yves Lavandier, French director and producer
 * 1959  – Badou Ezzaki, Moroccan footballer and manager
 * 1960 – Linford Christie, Jamaican-English sprinter
 * 1960  – Brad Jones, Australian race car driver
 * 1960  – Pascale Nadeau, Canadian journalist
 * 1961 – Buddy Jewell, American singer-songwriter
 * 1961  – Christopher Meloni, American actor
 * 1961  – Keren Woodward, English singer-songwriter
 * 1962 – Pierre Carles, French director and producer
 * 1962  – Billy Dean, American singer-songwriter and guitarist
 * 1962  – Clark Gregg, American actor
 * 1963 – Karl Beattie, English director and producer
 * 1963  – Mike Gascoyne, English engineer
 * 1964 – Pete Incaviglia, American baseball player and coach
 * 1964  – Jonathon Sharkey, American wrestler
 * 1965 – Rodney King, American victim of police brutality (d. 2012)
 * 1966 – Bill Romanowski, American football player and actor
 * 1966  – Teddy Sheringham, English international footballer and coach
 * 1967 – Greg Camp, American singer-songwriter and guitarist
 * 1967  – Phil Demmel, American guitarist and songwriter
 * 1969 – Ajay Devgn, Indian actor, director, and producer
 * 1971 – Edmundo Alves de Souza Neto, Brazilian footballer
 * 1971  – Jason Lewry, English cricketer
 * 1971  – Todd Woodbridge, Australian tennis player and sportscaster
 * 1972 – Eyal Berkovic, Israeli footballer
 * 1972  – Remo D'Souza, Indian choreographer and dancer
 * 1972  – Calvin Davis, American sprinter and hurdler (d. 2023)
 * 1972  – Zane Lamprey, American actor, director, producer, and screenwriter
 * 1973 – Dmitry Lipartov, Russian footballer
 * 1973  – Roselyn Sánchez, Puerto Rican-American actress
 * 1973  – Aleksejs Semjonovs, Latvian footballer
 * 1974 – Tayfun Korkut, Turkish football manager and former player
 * 1975 – Nate Huffman, American basketball player (d. 2015)
 * 1975  – Randy Livingston, American basketball player
 * 1975  – Katrin Rutschow-Stomporowski, German rower
 * 1975  – Pattie Mallette, Canadian author and film producer
 * 1975  – Pedro Pascal, Chilean and American actor
 * 1976 – Andreas Anastasopoulos, Greek shot putter
 * 1976  – Rory Sabbatini, South African golfer
 * 1977 – Per Elofsson, Swedish skier
 * 1977  – Michael Fassbender, German-Irish actor and producer
 * 1977  – Hanno Pevkur, Estonian lawyer and politician, Estonian Minister of Justice
 * 1980 – Avi Benedi, Israeli singer and songwriter
 * 1980  – Adam Fleming, Scottish journalist
 * 1980  – Gavin Heffernan, Canadian director and screenwriter
 * 1980  – Ricky Hendrick, American race car driver (d. 2004)
 * 1980  – Wairangi Koopu, New Zealand rugby league player
 * 1980  – Carlos Salcido, Mexican international footballer
 * 1981 – Michael Clarke, Australian cricketer
 * 1981  – Kapil Sharma, Indian stand-up comedian, television presenter and actor
 * 1982 – Marco Amelia, Italian footballer
 * 1982  – David Ferrer, Spanish tennis player
 * 1983 – Arthur Boka, Ivorian footballer
 * 1983  – Maksym Mazuryk, Ukrainian pole vaulter
 * 1984 – Engin Atsür, Turkish basketball player
 * 1984  – Nóra Barta, Hungarian diver
 * 1984  – Jérémy Morel, French footballer
 * 1984  – Miguel Ángel Moyá, Spanish footballer
 * 1985 – Thom Evans, Zimbabwean-Scottish rugby player
 * 1985  – Stéphane Lambiel, Swiss figure skater
 * 1986 – Ibrahim Afellay, Dutch footballer
 * 1986  – Andris Biedriņš, Latvian basketball player
 * 1987  – Pablo Aguilar, Paraguayan footballer
 * 1987  – Shane Lowry, Irish Professional Golfer, winner of the 2019 Open Championship and European Team Member for the 2021 and 2023 Ryder Cups
 * 1988 – Jesse Plemons, American actor
 * 1990 – Yevgeniya Kanayeva, Russian gymnast
 * 1990  – Miralem Pjanić, Bosnian footballer
 * 1990  – Amr El Solia, Egyptian footballer
 * 1991 – Quavo, American rapper
 * 1993 – Keshorn Walcott, Trinidadian javelin thrower
 * 1993  – Bruno Zuculini, Argentine footballer
 * 1994 – Pascal Siakam, Cameroonian basketball player
 * 1995 – Zack Steffen, American soccer player
 * 1996 – Zach Bryan, American singer-songwriter
 * 1996  – André Onana, Cameroonian footballer
 * 1997 – Dillon Bassett, American race car driver
 * 1997  – Abdelhak Nouri, Dutch footballer
 * 1997  – Austin Riley, American baseball player
 * 2000 – Rodrigo Riquelme, Spanish footballer
 * 2002 – Emma Myers, American actress
 * 2004 – Diana Shnaider, Russian tennis player
 * 2007 – Brenda Fruhvirtová, Czech tennis player

Pre-1600

 * 670 – Hasan ibn Ali the second Shia Imam (b. 624)
 * 870 – Æbbe the Younger, Frankish abbess
 * 872 – Muflih al-Turki, Turkish general
 * 968 – Yuan Dezhao, Chinese chancellor (b. 891)
 * 991 – Bardas Skleros, Byzantine general
 * 1118 – Baldwin I, king of Jerusalem
 * 1244 – Henrik Harpestræng, Danish botanical and medical author
 * 1272 – Richard, 1st Earl of Cornwall, English husband of Sanchia of Provence (b. 1209)
 * 1335 – Henry of Bohemia (b. 1265)
 * 1412 – Ruy González de Clavijo, Spanish explorer and author
 * 1416 – Ferdinand I, king of Aragon (b. 1379)
 * 1502 – Arthur, prince of Wales (b. 1486)
 * 1507 – Francis of Paola, Italian friar and saint, founded the Order of the Minims (b. 1416)
 * 1511 – Bernard VII, Lord of Lippe, German nobleman (b. 1428)

1601–1900

 * 1640 – Maciej Kazimierz Sarbiewski, Polish author and poet (b. 1595)
 * 1657 – Ferdinand III, Holy Roman Emperor (b. 1608)
 * 1657  – Jean-Jacques Olier, French priest, founded the Society of Saint-Sulpice (b. 1608)
 * 1672 – Pedro Calungsod, Filipino missionary and saint (b. 1654)
 * 1672  – Diego Luis de San Vitores, Spanish Jesuit missionary (b. 1627)
 * 1720 – Joseph Dudley, English politician, Governor of the Province of Massachusetts Bay (b. 1647)
 * 1742 – James Douglas, Scottish physician and anatomist (b. 1675)
 * 1747 – Johann Jacob Dillenius, German-English botanist and mycologist (b. 1684)
 * 1754 – Thomas Carte, English historian and author (b. 1686)
 * 1787 – Thomas Gage, English general and politician, Governor of the Province of Massachusetts Bay (b. 1719)
 * 1791 – Honoré Gabriel Riqueti, comte de Mirabeau, French journalist and politician (b. 1749)
 * 1801 – Thomas Dadford, Jr., English engineer (b. 1761)
 * 1803 – Sir James Montgomery, 1st Baronet, Scottish judge and politician (b. 1721)
 * 1817 – Johann Heinrich Jung, German author and academic (b. 1740)
 * 1827 – Ludwig Heinrich Bojanus, German physician and educator (b. 1776)
 * 1845 – Philip Charles Durham, Scottish admiral and politician (b. 1763)
 * 1865 – A. P. Hill, American general (b. 1825)
 * 1872 – Samuel Morse, American painter and academic, invented the Morse code (b. 1791)
 * 1891 – Albert Pike, American lawyer and general (b. 1809)
 * 1891  – Ahmed Vefik Pasha, Greek playwright and politician, 249th Grand Vizier of the Ottoman Empire (b. 1823)
 * 1894 – Achille Vianelli, Italian painter and academic (b. 1803)
 * 1896 – Theodore Robinson, American painter and academic (b. 1852)

1901–present

 * 1914 – Paul Heyse, German author, poet, and translator, Nobel Prize laureate (b. 1830)
 * 1917 – Bryn Lewis, Welsh international rugby player (b. 1891)
 * 1923 – Topal Osman, Turkish colonel (b. 1883)
 * 1928 – Theodore William Richards, American chemist and academic, Nobel Prize laureate (b. 1868)
 * 1930 – Zewditu I of Ethiopia (b. 1876)
 * 1933 – Ranjitsinhji, Indian cricketer (b. 1872)
 * 1936 – Jean Baptiste Eugène Estienne, French general (b. 1860)
 * 1942 – Édouard Estaunié, French novelist (b. 1862)
 * 1948 – Sabahattin Ali, Turkish journalist, author, and poet (b. 1907)
 * 1953 – Hugo Sperrle, German field marshal (b. 1885)
 * 1954 – Hoyt Vandenberg, US Air Force general (b. 1899)
 * 1966 – C. S. Forester, English novelist  (b. 1899)
 * 1972 – Franz Halder, German general (b. 1884)
 * 1972  – Toshitsugu Takamatsu, Japanese martial artist and educator (b. 1887)
 * 1974 – Georges Pompidou, French banker and politician, 19th President of France (b. 1911)
 * 1977 – Walter Wolf, German academic and politician (b. 1907)
 * 1987 – Buddy Rich, American drummer, songwriter, and bandleader (b. 1917)
 * 1989 – Manolis Angelopoulos, Greek singer (b. 1939)
 * 1992 – Juanito, Spanish footballer and manager (b. 1954)
 * 1992  – Jan van Aartsen, Dutch politician (b. 1909)
 * 1994 – Betty Furness, American actress, consumer advocate, game show panelist, television journalist and television personality (b. 1916)
 * 1994  – Marc Fitch, British historian and philanthropist (b. 1908)
 * 1995 – Hannes Alfvén, Swedish physicist and engineer, Nobel Prize laureate (b. 1908)
 * 1997 – Tomoyuki Tanaka, Japanese director and producer (b. 1910)
 * 1998 – Rob Pilatus, American-German singer-songwriter (b. 1965)
 * 2001 – Charles Daudelin, Canadian sculptor and painter (b. 1920)
 * 2002 – Levi Celerio, Filipino composer and songwriter (b. 1910)
 * 2002  – John R. Pierce, American engineer and author (b. 1910)
 * 2003 – Edwin Starr, American singer-songwriter (b. 1942)
 * 2004 – John Argyris, Greek computer scientist, engineer, and academic (b. 1913)
 * 2005 – Lillian O'Donnell, American crime novelist (b. 1926)
 * 2005  – Pope John Paul II (b. 1920)
 * 2006 – Lloyd Searwar, Guyanese anthologist and diplomat (b. 1925)
 * 2007 – Henry L. Giclas, American astronomer and academic (b. 1910)
 * 2008 – Yakup Satar, Turkish World War I veteran (b. 1898)
 * 2009 – Albert Sanschagrin, Canadian bishop (b. 1911)
 * 2009  – Bud Shank, American saxophonist and flute player (b. 1926)
 * 2010 – Chris Kanyon, American wrestler (b. 1970)
 * 2011 – John C. Haas, American businessman and philanthropist (b. 1918)
 * 2012 – Jesús Aguilarte, Venezuelan captain and politician (b. 1959)
 * 2012  – Elizabeth Catlett, American-Mexican sculptor and illustrator (b. 1915)
 * 2012  – Mauricio Lasansky, American graphic designer and academic (b. 1914)
 * 2013 – Fred, French author and illustrator (b. 1931)
 * 2013  – Jesús Franco, Spanish director, screenwriter, producer, and actor (b. 1930)
 * 2013  – Milo O'Shea, Irish-American actor (b. 1926)
 * 2014 – Urs Widmer, Swiss author and playwright (b. 1938)
 * 2015 – Manoel de Oliveira, Portuguese actor, director, producer, and screenwriter (b. 1908)
 * 2015  – Robert H. Schuller, American pastor and author (b. 1926)
 * 2015  – Steve Stevaert, Belgian businessman and politician, Governor of Limburg (b. 1954)
 * 2016 – Gallieno Ferri, Italian comic book artist and illustrator (b. 1929)
 * 2016  – Robert Abajyan, Armenian sergeant (b. 1996)
 * 2017 – Alma Delia Fuentes, Mexican actress (b. 1937)
 * 2021 – Simon Bainbridge, British composer (b. 1952)
 * 2022 – Estelle Harris, American actress and comedian (b. 1928)
 * 2024 – Jerry Abbott, American country music songwriter and record producer (b. 1942)
 * 2024 – John Barth, American writer (b. 1930)
 * 2024 – Maryse Condé, Guadeloupean novelist, critic, and playwright (b. 1934)
 * 2024 – Christopher Durang, American playwright (b. 1949)
 * 2024 – Larry Lucchino, American attorney and baseball executive (b. 1945)
 * 2024 – John Sinclair, American poet (b. 1941)
 * 2024 – Juan Vicente Pérez, Venezuelan supercentenarian (b. 1909)

Holidays and observances

 * Christian feast day:
 * Abundius of Como
 * Amphianus of Lycia
 * Æbbe the Younger
 * Bronach of Glen-Seichis (Irish martyrology)
 * Francis of Paola
 * Francisco Coll Guitart
 * Henry Budd (Anglican Church of Canada)
 * Nicetius of Lyon
 * Pedro Calungsod
 * Theodosia of Tyre
 * Urban of Langres
 * April 2 (Eastern Orthodox liturgics)
 * International Children's Book Day (International)
 * Thai Heritage Conservation Day (Thailand)
 * Unity of Peoples of Russia and Belarus Day (Belarus)
 * World Autism Awareness Day (International)
 * Malvinas Day (Argentina)

title: April 2


text:
Acetylene

Acetylene (systematic name: ethyne) is the chemical compound with the formula C2H2 and structure H\sC\tC\sH. It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure form and thus is usually handled as a solution. Pure acetylene is odorless, but commercial grades usually have a marked odor due to impurities such as divinyl sulfide and phosphine.

As an alkyne, acetylene is unsaturated because its two carbon atoms are bonded together in a triple bond. The carbon–carbon triple bond places all four atoms in the same straight line, with CCH bond angles of 180°.

Discovery
Acetylene was discovered in 1836 by Edmund Davy, who identified it as a "new carburet of hydrogen". It was an accidental discovery while attempting to isolate potassium metal. By heating potassium carbonate with carbon at very high temperatures, he produced a residue of what is now known as potassium carbide, (K2C2), which reacted with water to release the new gas. It was rediscovered in 1860 by French chemist Marcellin Berthelot, who coined the name acétylène. Berthelot's empirical formula for acetylene (C4H2), as well as the alternative name "quadricarbure d'hydrogène" (hydrogen quadricarbide), were incorrect because many chemists at that time used the wrong atomic mass for carbon (6 instead of 12). Berthelot was able to prepare this gas by passing vapours of organic compounds (methanol, ethanol, etc.) through a red hot tube and collecting the effluent. He also found that acetylene was formed by sparking electricity through mixed cyanogen and hydrogen gases. Berthelot later obtained acetylene directly by passing hydrogen between the poles of a carbon arc.

Preparation
Except in China acetylene production is dominated by partial combustion of natural gas.

Partial combustion of hydrocarbons
Since the 1950s, acetylene has mainly been manufactured by the partial combustion of methane. It is a recovered side product in production of ethylene by cracking of hydrocarbons. Approximately 400,000 tonnes were produced by this method in 1983. Its presence in ethylene is usually undesirable because of its explosive character and its ability to poison Ziegler–Natta catalysts. It is selectively hydrogenated into ethylene, usually using Pd–Ag catalysts.

3 CH4 + 3 O2 → C2H2 + CO + 5 H2O.

Partial combustion of methane also produces acetylene:

Dehydrogenation of alkanes
The heaviest alkanes in petroleum and natural gas are cracked into lighter molecules which are dehydrogenated at high temperature:

 * C2H6 → C2H2 + 2 H2
 * 2 CH4→ C2H2+ 3 H2

This last reaction is implemented in the process of anaerobic decomposition of methane by microwave plasma. The advantage of this technology is the absence of CO2 emissions and the joint production of hydrogen as a secondary product. It makes it a low-carbon technology production and also an electrified process. For 32 t of methane transformed, production of 26 t of acetylene and 6 t of hydrogen (according to stoichiometry).

Carbochemical method
Acetylene is traditionally produced by hydrolysis (reaction with water) of calcium carbide:
 * CaC2 + 2 H2O -> Ca(OH)2 + C2H2

1 kg of calcium carbide combines with 562.5 g of water to release 350 liters of acetylene. This reaction was discovered by Friedrich Wöhler in 1862.

The use of this technology has declined worldwide with the notable exception of China, with its emphasis on coal-based chemical industry. Otherwise oil has increasingly supplanted coal as the chief source of reduced carbon.

Calcium carbide production requires high temperatures, ~2000 °C, necessitating the use of an electric arc furnace. In the US, this process was an important part of the late-19th century revolution in chemistry enabled by the massive hydroelectric power project at Niagara Falls.

Bonding
In terms of valence bond theory, in each carbon atom the 2s orbital hybridizes with one 2p orbital thus forming an sp hybrid. The other two 2p orbitals remain unhybridized. The two ends of the two sp hybrid orbital overlap to form a strong σ valence bond between the carbons, while on each of the other two ends hydrogen atoms attach also by σ bonds. The two unchanged 2p orbitals form a pair of weaker π bonds.

Since acetylene is a linear symmetrical molecule, it possesses the D∞h point group.

Changes of state
At atmospheric pressure, acetylene cannot exist as a liquid and does not have a melting point. The triple point on the phase diagram corresponds to the melting point (−80.8 °C) at the minimal pressure at which liquid acetylene can exist (1.27 atm). At temperatures below the triple point, solid acetylene can change directly to the vapour (gas) by sublimation. The sublimation point at atmospheric pressure is −84.0 °C.

Other
At room temperature, the solubility of acetylene in acetone is 27.9 g per kg. For the same amount of dimethylformamide (DMF), the solubility is 51 g. At 20.26 bar, the solubility increases to 689.0 and 628.0 g for acetone and DMF, respectively. These solvents are used in pressurized gas cylinders.

Welding
Approximately 20% of acetylene is supplied by the industrial gases industry for oxyacetylene gas welding and cutting due to the high temperature of the flame. Combustion of acetylene with oxygen produces a flame of over 3600 K, releasing 11.8 kJ/g. Oxygen with acetylene is the hottest burning common gas mixture. Acetylene is the third-hottest natural chemical flame after dicyanoacetylene's 5260 K and cyanogen at 4798 K. Oxy-acetylene welding was a popular welding process in previous decades. The development and advantages of arc-based welding processes have made oxy-fuel welding nearly extinct for many applications. Acetylene usage for welding has dropped significantly. On the other hand, oxy-acetylene welding equipment is quite versatile – not only because the torch is preferred for some sorts of iron or steel welding (as in certain artistic applications), but also because it lends itself easily to brazing, braze-welding, metal heating (for annealing or tempering, bending or forming), the loosening of corroded nuts and bolts, and other applications. Bell Canada cable-repair technicians still use portable acetylene-fuelled torch kits as a soldering tool for sealing lead sleeve splices in manholes and in some aerial locations. Oxyacetylene welding may also be used in areas where electricity is not readily accessible. Oxyacetylene cutting is used in many metal fabrication shops. For use in welding and cutting, the working pressures must be controlled by a regulator, since above 15 psi, if subjected to a shockwave (caused, for example, by a flashback), acetylene decomposes explosively into hydrogen and carbon.

Chemicals
Acetylene is useful for many processes, but few are conducted on a commercial scale.

One of the major chemical applications is ethynylation of formaldehyde. Acetylene adds to aldehydes and ketones to form α-ethynyl alcohols:
 * Reppe-chemistry-endiol-V1.svg

The reaction gives butynediol, with propargyl alcohol as the by-product. Copper acetylide is used as the catalyst.

In addition to ethynylation, acetylene reacts with carbon monoxide, acetylene reacts to give acrylic acid, or acrylic esters. Metal catalysts are required. These derivatives form products such as acrylic fibers, glasses, paints, resins, and polymers. Except in China, use of acetylene as a chemical feedstock has declined by 70% from 1965 to 2007 owing to cost and environmental considerations. In China, acetylene is a major precursor to vinyl chloride.

Historical uses
Prior to the widespread use of petrochemicals, coal-derived acetylene was a building block for several industrial chemicals. Thus acetylene can be hydrated to give acetaldehyde, which in turn can be oxidized to acetic acid. Processes leading to acrylates were also commercialized. Almost all of these processes became obsolete with the availability of petroleum-derived ethylene and propylene.

Niche applications
In 1881, the Russian chemist Mikhail Kucherov described the hydration of acetylene to acetaldehyde using catalysts such as mercury(II) bromide. Before the advent of the Wacker process, this reaction was conducted on an industrial scale.

The polymerization of acetylene with Ziegler–Natta catalysts produces polyacetylene films. Polyacetylene, a chain of CH centres with alternating single and double bonds, was one of the first discovered organic semiconductors. Its reaction with iodine produces a highly electrically conducting material. Although such materials are not useful, these discoveries led to the developments of organic semiconductors, as recognized by the Nobel Prize in Chemistry in 2000 to Alan J. Heeger, Alan G MacDiarmid, and Hideki Shirakawa.

In the 1920s, pure acetylene was experimentally used as an inhalation anesthetic.

Acetylene is sometimes used for carburization (that is, hardening) of steel when the object is too large to fit into a furnace.

Acetylene is used to volatilize carbon in radiocarbon dating. The carbonaceous material in an archeological sample is treated with lithium metal in a small specialized research furnace to form lithium carbide (also known as lithium acetylide). The carbide can then be reacted with water, as usual, to form acetylene gas to feed into a mass spectrometer to measure the isotopic ratio of carbon-14 to carbon-12.

Acetylene combustion produces a strong, bright light and the ubiquity of carbide lamps drove much acetylene commercialization in the early 20th century. Common applications included coastal lighthouses, street lights, and automobile and mining headlamps. In most of these applications, direct combustion is a fire hazard, and so acetylene has been replaced, first by incandescent lighting and many years later by low-power/high-lumen LEDs. Nevertheless, acetylene lamps remain in limited use in remote or otherwise inaccessible areas and in countries with a weak or unreliable central electric grid.

Natural occurrence
The energy richness of the C≡C triple bond and the rather high solubility of acetylene in water make it a suitable substrate for bacteria, provided an adequate source is available. A number of bacteria living on acetylene have been identified. The enzyme acetylene hydratase catalyzes the hydration of acetylene to give acetaldehyde:

 * C2H2 + H2O -> CH3CHO

Acetylene is a moderately common chemical in the universe, often associated with the atmospheres of gas giants. One curious discovery of acetylene is on Enceladus, a moon of Saturn. Natural acetylene is believed to form from catalytic decomposition of long-chain hydrocarbons at temperatures of 1700 K and above. Since such temperatures are highly unlikely on such a small distant body, this discovery is potentially suggestive of catalytic reactions within that moon, making it a promising site to search for prebiotic chemistry.

Vinylation reactions
In vinylation reactions, H−X compounds add across the triple bond. Alcohols and phenols add to acetylene to give vinyl ethers. Thiols give vinyl thioethers. Similarly, vinylpyrrolidone and vinylcarbazole are produced industrially by vinylation of 2-pyrrolidone and carbazole.
 * Reppe-chemnistry-vinylization.png

The hydration of acetylene is a vinylation reaction, but the resulting vinyl alcohol isomerizes to acetaldehyde. The reaction is catalyzed by mercury salts. This reaction once was the dominant technology for acetaldehyde production, but it has been displaced by the Wacker process, which affords acetaldehyde by oxidation of ethylene, a cheaper feedstock. A similar situation applies to the conversion of acetylene to the valuable vinyl chloride by hydrochlorination vs the oxychlorination of ethylene.

Vinyl acetate is used instead of acetylene for some vinylations, which are more accurately described as transvinylations. Higher esters of vinyl acetate have been used in the synthesis of vinyl formate.

Organometallic chemistry
Acetylene and its derivatives (2-butyne, diphenylacetylene, etc.) form complexes with transition metals. Its bonding to the metal is somewhat similar to that of ethylene complexes. These complexes are intermediates in many catalytic reactions such as alkyne trimerisation to benzene, tetramerization to cyclooctatetraene, and carbonylation to hydroquinone:
 * Reppe-chemistry-benzene.png
 * Reppe-chemistry-cyclooctatetraene.png
 * Fe(CO)5 + 4 C2H2 + 2 H2O -> 2 C6H4(OH)2 + FeCO3 at basic conditions (50–$80 degC$, 20–$25 atm$).

Metal acetylides, species of the formula L_{n}M\sC2R, are also common. Copper(I) acetylide and silver acetylide can be formed in aqueous solutions with ease due to a favorable solubility equilibrium.

Acid-base reactions
Acetylene has a pKa of 25, acetylene can be deprotonated by a superbase to form an acetylide:

Various organometallic and inorganic reagents are effective.

Hydrogenation
Acetylene can be semihydrogenated to ethylene, providing a feedstock for a variety of polyethylene plastics. Halogens add to the triple bond.

Safety and handling
Acetylene is not especially toxic, but when generated from calcium carbide, it can contain toxic impurities such as traces of phosphine and arsine, which give it a distinct garlic-like smell. It is also highly flammable, as are most light hydrocarbons, hence its use in welding. Its most singular hazard is associated with its intrinsic instability, especially when it is pressurized: under certain conditions acetylene can react in an exothermic addition-type reaction to form a number of products, typically benzene and/or vinylacetylene, possibly in addition to carbon and hydrogen. Consequently, acetylene, if initiated by intense heat or a shockwave, can decompose explosively if the absolute pressure of the gas exceeds about 200 kPa. Most regulators and pressure gauges on equipment report gauge pressure, and the safe limit for acetylene therefore is 101 kPagage, or 15 psig. It is therefore supplied and stored dissolved in acetone or dimethylformamide (DMF), contained in a gas cylinder with a porous filling, which renders it safe to transport and use, given proper handling. Acetylene cylinders should be used in the upright position to avoid withdrawing acetone during use.

Information on safe storage of acetylene in upright cylinders is provided by the OSHA, Compressed Gas Association, United States Mine Safety and Health Administration (MSHA), EIGA, and other agencies.

Copper catalyses the decomposition of acetylene, and as a result acetylene should not be transported in copper pipes.

Cylinders should be stored in an area segregated from oxidizers to avoid exacerbated reaction in case of fire/leakage. Acetylene cylinders should not be stored in confined spaces, enclosed vehicles, garages, and buildings, to avoid unintended leakage leading to explosive atmosphere. In the US, National Electric Code (NEC) requires consideration for hazardous areas including those where acetylene may be released during accidents or leaks. Consideration may include electrical classification and use of listed Group A electrical components in US. Further information on determining the areas requiring special consideration is in NFPA 497. In Europe, ATEX also requires consideration for hazardous areas where flammable gases may be released during accidents or leaks.

title: Acetylene


text:
Alfred

Alfred may refer to:

Arts and entertainment

 * Alfred J. Kwak, Dutch-German-Japanese anime television series
 * Alfred (Arne opera), a 1740 masque by Thomas Arne
 * Alfred (Dvořák), an 1870 opera by Antonín Dvořák
 * "Alfred (Interlude)" and "Alfred (Outro)", songs by Eminem from the 2020 album Music to Be Murdered By

Business and organisations

 * Alfred, a radio station in Shaftesbury, England
 * Alfred Music, an American music publisher
 * Alfred University, New York, U.S.
 * The Alfred Hospital, a hospital in Melbourne, Australia

People

 * Alfred (name) includes a list of people and fictional characters called Alfred
 * Alfred the Great (848/49 – 899), or Alfred I, a king of the West Saxons and of the Anglo-Saxons

Antarctica

 * Mount Alfred (Antarctica)

Australia

 * Alfredtown, New South Wales
 * County of Alfred, South Australia

Canada

 * Alfred and Plantagenet, Ontario
 * Alfred, Ontario, a community in Alfred and Plantagenet
 * Alfred Island, Nunavut
 * Mount Alfred, British Columbia

United States

 * Alfred, Maine, a New England town
 * Alfred (CDP), Maine, the main village in the town
 * Alfred, New York, a town
 * Alfred (village), New York, within the town of Alfred
 * Alfred, North Dakota
 * Alfred, Texas
 * Lake Alfred, Florida

Other uses

 * HMS Alfred, the name of several ships of the Royal Navy
 * USS Alfred, launched in 1774 as Black Prince
 * Alfred (software), an application launcher for macOS
 * ALFRED (nuclear reactor), lead-cooled fast reactor demonstrator
 * Allele Frequency Net Database, an electronic database of genetic alleles

title: Alfred