8 THE GASES IN ROCKS. 



from the decomposition of sulphate of iron. In all, 57.87 volumes were 

 obtained: C0 2 , 12.77; CO, 1.96; CH 4 , 1.50; N 2 , 0.56; SO 2 , 83. Leaving 

 out the S0 2 , 9.8 volumes remain, as follows: C0 2 , 76.05; CO, 11.67; CH 4 , 

 8.93; N 2 , 3.33. This analysis, the most remarkable of the series, though 

 Dewar does not mention the fact, shows a complete absence of hydrogen 

 (an uncommon phenomenon), while the percentage of marsh-gas is unusu- 

 ally high. There is, however, reason to suspect that there was hydrogen 

 liberated, but that it was oxidized to water by the action of the iron com- 

 pound, following the decomposition of the sulphate. 



In 1888 W. F. Hillebrand 1 discovered that the mineral uraninite when 

 treated with acids slowly disengaged bubbles of gas. As the result of a 

 well-selected series of tests this appeared, in the light of the chemical 

 knowledge of that day, to be nitrogen. Trials with different varieties of 

 the mineral revealed a rather significant relation between the percentage of 

 uranyl and this gas. The greater the amount of the oxide, the more gas 

 obtained. 



Several years later, Sir William Ramsay's scepticism was aroused when 

 his attention was called to the paper by Hillebrand, for he hesitated to be- 

 lieve that free nitrogen could be produced by treating any substance with 

 sulphuric acid. To test the case, he decomposed cleveite with this acid, 

 obtaining little nitrogen, but some 20 cubic centimeters of argon, which 

 the spectroscope showed to be mixed with some other gas. 2 A brilliant 

 yellow line which appeared in this spectrum coincided exactly with D 3 , the 

 so-called " helium " line, first discovered in the spectrum of the chromo- 

 sphere of the sun by Sir Norman Lockyer in 1868. This was the first real 

 acquaintance with helium, until then known only as a hypothetical sub- 

 stance existing in the sun. Lockyer immediately became interested in this 

 discovery of helium in a terrestrial mineral, and attempted to prove that 

 it was not a single gas, but a compound or a mixture of gases, basing his 

 contention upon various strange lines in the spectrum. 3 



Ramsay, continuing his study of the gas from cleveite, perceived what 

 had been previously overlooked, namely, that hydrogen generally was more 

 abundant than helium in one case amounting to 80 per cent of the total 

 gas. The hypothesis that this hydrogen might have been formed by the 

 breaking up of an unstable hydride, the form in which Ramsay thought 

 the helium should be evolved, if it were derived from combination with the 

 uranium or yttrium of the mineral, was put to the test, with the result 

 that the evidence pointed strongly against the theory. 4 A series of miner- 

 als powdered and fused with potassium acid sulphate were found to yield 

 gas, sometimes helium, 5 but oftener hydrogen and the oxides of carbon. 6 



In 1896 W. A. Tilden made an attempt to determine the condition in 

 which helium and the associated gases exist in minerals. Argon and helium 

 were of particular interest, for Tilden believed that these two elements will 



1 W. F. Hillebrand, Bull. 78, U. S. G. S., pp. 43-79. 



2 Sir William Ramsay, Proc. Roy. Soc., vol. 58 (1895), pp. 65-67. 



3 Sir J. N. Lockyer, a series of six short papers in Proc. Roy. Soc., vols. 58, 59, and 60. 



4 Ramsay, Proc. Roy. Soc., vol. 58, pp. 81-89. 



5 Ramsay, Proc. Roy. Soc., vol. 59, pp. 325-330. 

 "Ramsay and Travers, Proc. Roy. Soc., vol. 60, pp. 442-448. 



