Page:Proceedings of the Royal Society of London Vol 60.djvu/486

Rh Kayser and Friedlander (‘ Chem. Zeitung,’ yoI. 9, p. 1529) have stated that in a vacuum-tube fitted with platinum electrodes, and containing atmospheric argon, the argon became absorbed by the deposited.0platinum, and the tube then showed certain of the helium lines I have never been able to absorb argon to more than the very slightest extent, and though I have often had argon-tubes, which have become black, owing to the deposition of platinum, through which a powerful discharge has passed for many hours, I have never noticed any marked absorption.

A specimen of argon, the lightest fraction obtained from Professor Ramsay’s diffusion experiments, was treated in the manner just described. After several hours’ circulation it was found that the gas absorbed by the platinum consisted only of argon, and no trace of helium could be detected. This process has also been applied to the analysis of the gases from certain mineral springs; the results of these experiments form the subject of another paper.

It has long been known* that many crystallised minerals contain gas enclosed in cavities in which drops of liquid are also frequently visible. The liquid often consists of water and aqueous solutions, occasionally of hydrocarbons, and not unfrequently of carbon dioxide, the latter being recognisable by the peculiarities of its behaviour under the application of heat. The liquid supposed to be carbon dioxide has been found in some cases to pass from the liquid to the gaseous state, and therefore to disappear, and to return from gas to liquid at temperatures lower by two or three degrees than the critical point of carbon dioxide. This seems to indicate the presence of some incondensable gas, and as H. Davy found nitrogen in the fluid cavities of quartz, it seemed probable that the alteration of the critical point was due to that gas.

My attention was drawn to this subject by the observation that Peterhead granite, when heated in a vacuum, gives off several times its volume of gas, consisting, to the extent of three-fourths of its volume, of hydrogen (‘ Roy. Soc. Proc.,’ vol. 59, p. 218).

Brewster, ‘ E. S. Edin. Trans.,’ 1824, vol. 10, p. 1; ‘Edin. J. Science,’ vol. 6, p. H5 ; Simmler, * Pogg. Ann.,’ vol. 105, p. 460; Sorby and Butler, ‘ Roy. Soc. Proc.,’ vol. 17, p. 291; Vogelsang and Gbissler, ‘ Pogg. Ann.,’ vol. 137, pp. 56 and 257; Hartley, ‘ 0. S. Trans.,’ 1876, vol. 1, p.137, and vol. 2, p. 237, also 1877, vol. 1, p. 241.
 * The chief literature of this subject is contained in the following papers: