· Who discovered oxygen? Is there any dispute over this?
Oxygen was originally discovered by Carl Wilhelm Scheele who was a Swedish apothecary in the 18th century. He was the first to discover it, which he did in 1772. Two other chemists are said to have independently discovered it, the first of the two was Joseph Priestly, he was an English chemist who independently discovered it in 1774, and the second of the two was Antoine Lavoirier, he also discovered it independently, who was the man to realise it was an element and name it oxygen in 1775.
There is a dispute over who discovered oxygen first given the time proximity between the three men, Joseph Priestly is often credited with the discovery as he was the first to publish his results (in 1774) due to Carl Wilhelm Scheele not publishing until 1777. Antoine Lavoirier is not a contender as although he was trying to determine what air was made of independently, it was Joseph Priestly who lead him in the right direction when he told Lavoirier of his experiment and findings.
· How was it discovered?
In 1772 Carl Wilhelm Scheele was the first to collect and discover oxygen. During the time of the discovery Scheele was in Sweden working as the assistant of Lokk, it was here that he that he made the first experiment to discover oxygen.
It may have been the first time that Oxygen had been discovered however Scheele found a number of ways to produce Oxygen. Strongly heating HgO and MnO2 and by heating silver carbonate or mercuric carbonate and then absorbing the CO2 by KOH. In the first method, he reacted nitric acid with KOH and/or K2CO3 which formed KNO3. Distilling the residue with sulfuric acid produced both NO2 and O2. The former was absorbed by Ca(OH)2(sat'd), leaving oxygen (fire air), during all of these experiments the contents were collected using a small bag.
AgCO3(s)
In 1774 Joseph Priestley attempted to complete the experiments that Scheele had completed two years earlier. Using a 12-inch-wide glass "burning lens", he focused sunlight on a lump of reddish mercuric oxide in an inverted glass container, the gas produced of course was oxygen which at the time priestly named “dephlogisticated air”. He then did experiments to test the characteristics of oxygen, he found that it burned intensely and that when mice where exposed to the gas they lived considerably longer, after finding that it was not harmful he then took breaths himself, he wrote: "The feeling of it to my lungs was not sensibly different from that of common air, but I fancied that my breast felt peculiarly light and easy for some time afterwards."
“this air is of exalted nature…A candle burned in this air with an amazing strength of flame; and a bit of red hot wood crackled and burned with a prodigious rapidity. But to complete the proof of the superior quality of this air, I introduced a mouse into it; and in a quantity in which, had it been common air, it would have died in about a quarter of an hour; it lived at two different times, a whole hour, and was taken out quite vigorous.”
· What were the contributions of the people involved?
Carl Wilhelm Scheele: the first to discover in Sweden, he did so in 1772 although he did not publish until 1777 which is why it was disputed as to who exactly discovered it due to Joseph Priestly publishing his work 3 years before in 1774. Although Scheele does now get the credit for discovering oxygen, it was not him who realised it was a chemical element and named it oxygen. He had originally called it “fire-air” however, due to his experiment which found blowing oxygen onto an open flame caused it to flare.
Joseph Priestly: was the second to discover oxygen in 1774, he published his results right away which led a lot of people to credit him with its discovery. He is now thought to be the second, yet independent, discoverer of oxygen. He two did not find it to be a chemical element or call it oxygen.
Antoine Lavoisier: the third to discover oxygen independently, although Priestly had led him in the right direction with his own experiments. Lavoirier does however get recognition as he was the one to find it to be a chemical element and call it oxygen (Greek word meaning “acid-former”, he named it thus as he thought all acids contained oxygen, this was later disproved).
· How did it move the new science of chemistry forward?
Oxygen is very important in chemistry; it reacts with almost all known elements to produce oxides. It as an ion has a negative 2 charge which means that the structure of molecules would be able to be predicted.
Without the discovery of oxygen we would never have been able to know as much as we do about living organisms and a whole array of other things on earth as well as the universe not least including the chemical make up of water! Oxygen is the most common element on earth, second most common in earths atmosphere and third most common element in the universe.
Oxygen has to do with so much in our world that not knowing about it would be a significant step back from our modern age.
References:
http://www.chemistry-help.info/Importance_of_Oxygen.html
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