184 THE EARL OF BERKELEY, MR. E. G. J. HARTLEY AND DR. C. V. BURTON: 



Rubber 

 Cubing 



Rubber 

 tubing 



Exit tube of 

 waCer vessel 



Rubber plug 



Fig. 1. 



Change in Weight of 2nd Solution Vessel. 



It was mentioned that the 2nd solution vessel always lost weight (see p. 163 of 

 vol. 77, A, 'Roy. Soc. Proc.'), and a possible explanation was suggested for this. Further 

 work with the method seemed to point to the absorption of moisture by the rubber 

 connecting piece as a possible cause of the difficulty. Fig. 2 (p. 185) shows the form of 

 joint devised to get over this. A is the exit tube of one vessel, and B the entry tube 

 of the next vessel. C is a rubber plug, cut on the lathe to the shape shown, and 

 secured in place by the "umbrella rings" D. The inverted U-tube E is similarly 

 held in place by F, and the space between the U-tube and the exit and entry tubes 

 A and B is partially filled with- mercury through the side tubes G, which are themselves 

 closed by rubber plugs. 



The following tests were made : 



Two vessels, containing sulphuric acid, were placed in series and dry air passed for 

 48 hours, with the result that each vessel gained 0'0006 gr. 



This experiment was repeated and air passed for 116 hours, at the end of which 

 the 1st vessel had gained 0'0022 gr., and the second 0'0032 gr. 



The experiment was again repeated, but the precaution was taken to dry the 

 rubber plugs in an air oven and keep them in a desiccator until use, as it might be 

 that these plugs gave up moisture to the mercury which passed it on to the air 



