334 On the Weight of Hydrogen desiccated hy Liquid Air. 



On the "Weight of Hydrogen desiccated by Liquid Air." By 

 Lord Eayleigh, F.E.S. Eeceived February 22, — Eead 

 April 5, 1900. 



In recent experiments by myself and by others upon the density of 

 hydrogen, the gas has always been dried by means of phosphoric 

 anhydride ; and a doubt may remain whether on the one hand the 

 removal of aqueous vapour is sufficiently complete, and on the other 

 v/hether some new impurity may not be introduced. I thought that it 

 would be interesting to weigh hydrogen dried in an entirely different 

 manner, and this I have recently been able to effect with the aid of 

 liquid air, acting as a cooling agent, supplied by the kindness of 

 Professor Dewar from the Eoyal Institution. The operations of filling 

 and weighing were carried out in the country as hitherto. I ought, 

 perhaps, to explain that the object was not so much to make a new 

 determination of the highest possible accuracy, as to test whether any 

 serious error could be involved in the use of phosphoric anhydride, 

 such as might explain the departure of the ratio of densities of oxygen 

 and hydrogen from that of 16 : 1. I may say at once that the result 

 was negative. 



Each supply consisted of about 6 litres of the liquid, contained in 

 two large vacuum- jacketed vessels of Professor Dewar's design, and it 

 sufficed for two fillings with hydrogen at an interval of two days. 

 The intermediate day was devoted to a weighing of the globe empty. 

 There were four fillings in all, but one proved to be abortive owing to 

 a discrepancy in the weights when the globe was empty, before and 

 after the filling. The gas was exposed to the action of the liquid air 

 during its passage in a slow stream of about half a litre per hour 

 through a tube of thin glass. 



I have said that the result was negative. In point of fact the actual 

 weights found were -^o to milligrams heavier than in the case of 

 hydrogen dried by phosphoric anhydride. But I doubt whether the 

 , small excess is of any significance. It seems improbable that it could 

 have been due to residual vapour, and it is perhaps not outside the 

 error of experiment, considering that the apparatus was not in the best 

 condition. 



