138 CHEMICAL DISCOVERY AND INVENTION 



To prepare argon 1 on a large scale air is freed from oxygen by 

 means of red-hot copper. It is then dried by means of soda lime 

 and phosphoric oxide, and the nitrogen is absorbed by passage 

 through a tube packed with magnesium turnings heated to 

 bright redness. The residual gas is then made to circulate 

 through an apparatus containing hot copper, copper oxide, 

 soda lime, and magnesium, by which the last traces of im- 

 purities are removed. 2 



Argon is a colourless gas 19-9 times heavier than hydrogen, 

 and therefore nearly 14 times heavier than air. It is soluble in 

 water to about the same small extent as oxygen, that is, approxi- 

 mately 4 volumes in 100 of water at common temperatures. 



All attempts to induce argon to enter into chemical com- 

 bination have proved abortive. Most drastic treatment was 

 applied and a great variety of reagents used, but argon remains 

 in all these circumstances unaltered. No substance of this kind 

 having been previously known it will be understood that the 

 ingenuity of the discoverers and the efforts of manj^ other 

 chemists were employed to settle this point conclusively. 



In the paper of which an account has just been given the 

 discoverers assume, provisionally, that the gas they had suc- 

 ceeding in isolating was a single substance and not a mixture of 

 gases. 



The density of argon being 19-9 the law of Avogadro indicates 

 that its molecular weight is 39-8. The molecule is believed to 

 consist of one atom only, and this is designated by the symbol A. 



At the anniversary, meeting of the Chemical Society on March 

 27th, 1895, a fresh surprise awaited the assembled chemists. 

 The discovery of a new element similar in character to argon 

 was announced by Professor Ramsay. In seeking a clue to 

 compounds of argon he was led to repeat experiments of Hille- 

 brand on the rare mineral clevite, which, when boiled with weak 

 sulphuric acid, gives off a gas hitherto supposed to be nitrogen. 



This gas proved to contain very little nitrogen with traces of 

 argon, but examination with the spectroscope showed that the 

 most prominent line was a brilliant yellow one very close to the 

 two lines of sodium, D x and D 2 , but only known up to this time 



1 The name is derived from the Greek (dv privative, tpyov work), in reference 

 to its chemical inactivity. 



2 Details are described in the original paper entitled "Argon, a New Con- 

 stituent of the Atmosphere," Proc. Royal Soc., 57 (1895), p. 265. 



