14 Ramsay, The Newly Discovered Elements. 



gas, if it contained any at all ; hence it was necessary to 

 prepare a large quantity from air. A description of the 

 method of preparation of 1 5 litres has been recently given 

 to the Royal Society, in a paper treating of the properties 

 of pure argon {Proceedings, vol. 64, p. 185). Suffice it to 

 say here that it was necessary to deal with no less than 

 1,500 litres of air ; that the oxygen was removed by 

 passage through a large iron tube containing red-hot 

 metallic copper ; and that the nitrogen was absorbed by 

 5 kilograms of metallic magnesium. The resulting crude 

 argon was further purified by passage through tubes 

 containing a mixture of freshly made lime and magnesium 

 dust — a mixture which yields calcium on heating to red- 

 ness — in order to remove the last traces of nitrogen. 



This argon was then liquefied by passing it into a 

 reservoir cooled to about — 205*^0. by means of liquid air, 

 boiling under a pressure of a few centimetres of mercury. 

 It yielded about I7'4 cubic centimetres; it formed a 

 colourless liquid, showing no absorption spectrum. On 

 raising the pressure on the liquid to that of the atmos- 

 phere, it boiled ; and the first fraction was collected 

 separately. This fraction was then liquefied in its turn in 

 a smaller apparatus, so far as was possible ; but a portion 

 resisted liquefaction, in spite of the utmost lowering of 

 temperature which Dr. Travers and I could produce by 

 causing the liquid air to boil at a low pressure, and in 

 spite of increasing the pressure on the gas to over two 

 atmospheres. This gas was weighed, and proved to have 

 the density 976, a number closely approaching to the 

 expected density, 10. It has a brilliant spectrum, con- 

 sisting of lines chiefly in the red and yellow, with a few 

 less conspicuous lines in the green. On photographing 

 the spectrum, an operation carried out by my assistant, 

 Mr. Baly, the characteristic yellow and green lines of 



