Properties of Dried Hydrogen Sulphide Gas. 471 



The law that the effect of a film when very thin is propor- 

 tional to the square of the thickness is of considerable interest. 

 It is here deduced upon the basis of Laplace's more special 

 hypothesis that the specific differences between various bodies 

 in relation to capillary properties may be represented by a 

 simple coefficient in the expression for the law of force. But 

 it is not difficult to see that the conclusion is really indepen- 

 dent of this restriction, and that it holds good even though 

 the law of force for every pair of bodies is entirely arbitrary. 



LIII. Some Properties of Dried Hydrogen Sulphide Gas. 

 By K. E. Hughes, B.Sc., F.C.S., Jesus College, Oxford*. 



IT was shown simultaneously by Thorpe that dry hydrogen 

 sulphide mixed with carbon-disulphide vapour is without 

 action on titanium sesquioxide (J. C. S. 1885, p. 492), and by 

 Veley (ibid. p. 484) that the same gas when dry is without 

 action on quicklime. In both cases the formation of a minute 

 trace of water as a consequence of the reactions should cause 

 them to proceed to their ultimate limit. A few months ago 

 Mr. Yeley suggested a similar investigation upon the condi- 

 tions of reactions of hydrogen sulphide upon .metallic oxides, 

 other than those mentioned above. 



Magnesia was selected as the first oxide, and the experi- 

 ment was so arranged as to determine whether the weight of 

 the oxide was in any respect altered by the passage of the 

 hydrogen-sulphide gas over it. 



By means of a T-tube connected up with a hydrogen-sul- 

 phide generator on the one limb, and a hydrogen generator 

 on the other, a flow of either gas could be obtained at will, 

 and at an easily regulated rate. 



The gas first passed through a wash-bottle, which at the 

 same time served to determine the rate of flow of the gas, 

 which flow was such that on an average about 2 bubbles per 

 second passed through. 



The gas was dried by three U- tubes containing calcium 

 chloride, and finally by a straight tube of pentoxide of phos- 

 phorus, containing at each end a loose plug of cotton-wool. 

 The experimental vessel containing the oxide was a U-tube 

 fitted with glass stoppers pierced, so that by simply revolving 

 these stoppers the U-tube was sealed. The outgoing gas was 

 then passed into a lime-tower ; it was noticed that unless this 

 lime was thoroughly slaked, the absorption of the gas was but 



* Communicated by Mr. V. H. Velev, M.A., University Museum, 

 Oxford. 



