494 PRINCIPLES OF CHEMISTRY 



this for tea days 1,500 c.c. of gas were reduced to 200 cc., and the density 

 increased to IG'l (if that of EL, - 1 and N 2 14). Further treatment of the 

 remainder brought the density up to 19-09. After adding a small quantity 

 of oxygen and repassing the gas through the apparatus, the density rose to 

 20-0. To obtain argon by this process Ramsay and Eayleigh (employing a 

 mercury air pump and mercury gasometers) once treated about 150 litres of 

 atmospheric nitrogen. On another occasion they treated 7,925 c.c. of air by 

 the oxidation method and obtained 65 c.c. of argon, which corresponds to 

 0'82 per cent. The density of the argon obtained by this means was nearly 

 19-7, while that obtained by the magnesium method varied between 19-09 

 and 20-88. 



Thus the first positive and very important fact respecting argon is that 

 its specific gravity is nearly 20 that is, that it is 20 times heavier than 

 hydrogen, while nitrogen is only 14 times and oxygen 16 times heavier than 

 hydrogen. This explains the difference observed by Bayleigh between the 

 -densities of nitrogen obtained from- its compounds and from the atmosphere 

 (Chapter V., Note 4 bis). At and 760 mm. a litre of the former gas weighs 

 1-2505 grm., while a litre of the latter weighs 1-2572, or taking H - 1, the 

 density of the first - 13-916, and of the latter = 13-991. If the density of 

 argon be taken as 20, it is contained in atmospheric nitrogen to the extent of 

 about 1'23 per cent, by volume, whilst air contains about 0-97 per cent, by 

 volume. 



When argon had been isolated the question naturally arose, was it a new 

 homogeneous substance having definite properties or was it a mixture of 

 gases ? The former may now be positively asserted, namely, that argon is a 

 peculiar gas previously unknown to chemistry. Such a conviction is in the 

 first place established by the fact that argon has a greater number of nega- 

 tive properties, a smaller capacity for reaction, than any other simple or 

 compound body known. The most inert gas known is nitrogen, but argon 

 far exceeds it in this respect. Thus nitrogen is absorbed at a red heat by many 

 metals, with the formation of nitrides, while argon, as is seen in the mode 

 of its preparation and by direct experiment, does not possess this property. 

 Nitrogen, under the action of electric sparks, combines with hydrogen in -the 

 presence of acids and with oxygen hi the presence of alkalis, while argon is 

 unable to do so, as is seen from the method of separation from nitrogen. 

 Bayleigh and Ramsay also proved that argon is unable to react with chlorine 

 (dry or moist) either directly or under the action of an electric discharge, or 

 with phosphorus or sulphur, at a red heat. Sodium, potassium, and tellurium 

 may be distilled in an atmosphere of argon without change. Fused caustic 

 soda, incandescent soda-lime, molten nitre, red-hot peroxide of sodium, 

 and the polysulphides of calcium and sodium also do not react with argon. 

 Platinum black does not absorb it, and spongy platinum is unable to excite its 

 reaction with oxygen or chlorine. Aqua regia, bromine water, and a mixture 

 of hydrochloric acid and KMn0 4 were also without action upon argon. Besides 

 which it is evident from the method of its preparation that it is not acted upon 

 by red-hot oxide of copper. All these facts exclude any possibility of argon con- 

 taining any already known body, and prove it to be the most inert of all the 

 gases known. But besides these negative points, the independency of argon is 



