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sufficiently low temperature all gases could be reduced to liquids. But it was not until 1823 that, at the instigation of Michael Faraday, Sir Humphrey Davy put that theory to the test of experiment, with some success. He failed with the three gases – oxygen, nitrogen and hydrogen. The first breakthrough was made by Cailletet and Pictet, who, though working independently, obtained a ‘dynamic’ through not a ‘static’ liquid as, say, the steam from a kettle bears to a cup of water. Other scientists, notably Wroblewski and Olszewski in Cracow, continued experiments in the liquefaction of oxygen and 1883 Olszewski announced to the French Academy that he had obtained oxygen in a completely liquid state, and that a few days later he had seen nitrogen as a liquid but that it had disappeared in a few seconds (note 20). James Dewar who always kept himself informed as to the work of leading scientists at home and overseas gave, shortly thereafter, a fascinating lecture at The Royal Institution using the apparatus of Cailletet and Pictet. Here were new worlds for him to conquer and like Wilfred Thesiger the traveller “he always felt a compulsion to go where others have not been”. No doubt he was inspired also by the thought that his predecessors Faraday and Davy had been two of the earliest experimentalists in the liquefaction of gases. James Dewar took up the work which had fallen from their hands and working in hyper-arctic regions he pioneered a path where never foot of man had trod. With the same heroic courage and dogged determination as Scott, Amundsen and Shackleton had shown in their explorations he pursued his investigations as he continued his journey towards the absolute zero – K degrees, which was his South Pole. In pursuit of his goal he turned the chemical laboratory in The Royal Institution into a virtual machine shop. True to form he sensed a further fresh field of enquiry waiting to be investigated, viz. the properties of matter under hitherto unattainable conditions of cold which the liquefaction of gases had rendered possible. The next period in his career may be called The Low Temperature Years, for the liquefaction of gas now became his chief, though by no means his only, concern. His interest in this subject goes back to the very early 1870s. In 1874 he read to The British Association for the Advancement of Science a paper on The Latent Heat of Liquid Gases the author having deduced a formula for calculating the latent heat of a gas from the known tension of that gas. In 1878, using Cailletet’s apparatus he demonstrated, for the first time in Britain, the liquefaction of oxygen at one of The Royal Institution’s Friday evening lectures and six years later on a similar occasion he notched up another first, by showing on an apparatus which he had constructed for optical projection the liquefaction of oxygen so that, to their delighted wonder, the audience could watch the process taking place. Later he devised and constructed a machine, weighing over two tons, from which liquefied oxygen could be drawn off in quantity by means of a valve to act as a cooling agent, by which time he was also producing liquid air at twenty litres per hour, occasioning the remark that Professor Dewar was supplying liquid air as if it were water.
On December 17th 1891 the President of the Royal Society at the commencement of their meeting, read to the Fellows a letter from Professor Dewar which had just come into his hand, stating that “at 3 p.m. that afternoon he had placed a quantity of liquid oxygen in the state of rapid ebullition in air (and therefore at a temperature of –181 Celsius) between the poles of the historic Faraday magnet in a cup-shaped piece of rock salt (which is not moistened by liquid oxygen, and therefore keeps it in the spheroidal state)” and to his surprise Professor Dewar saw the liquid oxygen, as soon as the magnet was stimulated, “suddenly leap up to the poles and remain there permanently attracted till it was evaporated”. He was to show also that liquid ozone followed the same pattern of behaviour as the liquid oxygen had done. In 1897, working along with Henri Moisson the French scientist who had brought his apparatus to The Royal Institution, James Dewar liquefied fluorine which he was to succeed in solidifying in 1903. Together they also carried out a study of its properties in the liquid state. The boiling point of fluorine is –187 Celsius and there is no sign of solidification at –210 Celsius. A little of the liquid fluorine spilt accidentally set fire to the wooden floor.
By this time almost all the natural gases, apart from hydrogen, had been liquefied and it was in his long and arduous attempt to achieve that goal, in which he was often baffled but never defeated, that when spraying liquid air and oxygen with the hydrogen jet he found that in a few minutes the liquids congealed in hard solids “like snow” – and thus, for the first time solid oxygen was produced. Encouraged by this he continued his endeavours... NEXT PAGE
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