“On the contrary, if the earth should be suddenly placed in a very cold temperature, for example, that of Jupiter or Saturn, the water of our rivers and seas, and, probably, the greatest number of liquids which we know would become solid.”
“Air,” according to this supposition, or at least a part of the air-like substances which compose it, “would doubtless cease to exist in its present form; it would be changed to a liquid state, and this change would produce new liquids of which we know nothing.”
Lavoisier was mistaken about the temperature of Jupiter and Saturn, but was right in his supposition that air would become a liquid; however, as experiment did not prove the theory, the prediction was forgotten and the question dropped. It slept a long time, for it was not until 1823 that it was revived by Faraday. The first experiments of this great philosopher were on this subject. He was but twenty-two when he made his first discovery, the liquefaction of chlorine. The details of this experiment have been told by Tyndall. It is well known that when chlorine gas and cold water are united, crystals are formed which contain to every molecule of chlorine ten molecules of water. Faraday put some of these into a closed tube and heated them until two separate liquids appeared; one was water, the other floated on the surface of the water, and a certain professor of Paris declared that it could be nothing but oil carelessly left in the vessel. Faraday having opened the tube, found that this substance began to boil, and then changed with an explosion into a green gas. It was chlorine. Faraday, who was quick-tempered, immediately took his revenge on the professor, to whom he wrote: “You will be pleased to know, sir, that the oil left by carelessness in my apparatus was nothing less than liquefied chlorine.”
This first success decided the career of the young chemist. He announced that all gases could be reduced to this state if subjected to a sufficient pressure, and he undertook a series of experiments, of which the success was doubtful, but the danger certain. He operated in this way: He took a thick glass tube in the form of an inverted U; one branch was left empty, in the other the materials for producing the gas to be studied were placed and the whole closed. Obliged to gather in the empty branch, the gas continually increased in pressure, and there were two possible results to the experiment; either the gas would not change its state, and the pressure would increase until the vessel broke, or when a certain limit of pressure was reached, then the liquid would appear and would continue to accumulate as long as the gas was disengaged. A dozen gases were reduced in this way; among them were the following, which we shall need: Ammonia, sulphurous acid, carbonic acid, and protoxide of nitrogen, which at a temperature of ten degrees required a pressure equal to sixty atmospheres.