﻿226 Mr. Bernard Cavanagh on 



That the mechanical deposition o£ gas on the walls of the 

 discharge vessel will not account entirely for the disappear- 

 ance of the gas is shown by the difference in the behaviour 

 of nitrogen and hydrogen with phosphorus, sulphur, and 

 iodine. Practically none of the nitrogen can be reliberated 

 by heating, but a large proportion of the hydrogen is evolved. 



There is reason for believing that the modification of 

 hydrogen is triatomic in nature. Wendt has shown in the 

 paper previously quoted that hydrogen drawn from a tube 

 through which an electric discharge is passing contains a 

 small quantity of H 3 . Probably monatomic hydrogen is first 

 formed, and owing to collision with neutral molecules of the 

 gas, H 3 then appears. The monatomic gas may be produced 

 originally by the action of the swift-moving electrons on the 

 molecules. Wendt and Grubb * have also shown that N 3 is 

 produced when an electric discharge passes through nitrogen. 

 Thomson f found evidence of H 3 in his positive-ray experi- 

 ments. It is this triatomic form of hydrogen which is 

 effective in the production of chemical compounds in the 

 electric discharge-tube. 



XVI. Molecular Thermodynamics. II. By Bernard 

 A. M. Cavanagh, B.A., Balliol College, Oxford %. 



I. Molecules, Thermodynamics, and 

 Quantum Theory. 



IN developing a molecular treatment of the thermodynamics 

 of dilute solutions in simple solvents, Planck § deter- 

 mined the form of the integration constants in the entropy 

 function by a method which was at the time the subject of 

 some controversy. 



M. Cantor || objected that the hypothetical transition to 

 the gaseous state without change of the molecular composition 

 was not even theoretically possible, since there probably 

 existed in the liquid state, complex molecules whose existence 

 was inseparably connected with the condensed state of the 

 phase, and entirely incompatible with a state of high 

 temperature and low pressure. 



* Science, vol. lii. (1920). 

 t Proc. Roy. Soc. A. vol. Ixxxix. (1913). 

 t Communicated by Dr. J. W. Nicholson, F.R.S. 

 § « Thermodynamics,' 1917 (Trans. Ogg), pp. 225-226. Or see Phil. 

 Mag. xliii. p. 608 (1922). 



'I Ann. der Phys. x. p. 205 (1903). 



