468 Mr. E. C. Grey. The Decomposition of 



the flask F is heated carefully and the contents brought to the boil ; the gas 

 displaces the mercury from the inner tube A, and should the gas evolved 

 be more than sufficient to fill A the tap D may be turned so as to connect 



A and B, and the tap E turned so as to connect B and C, while C is lowered ; 

 the mercury in B falls with a corresponding rise of mercury in A. 



The volume of the inner tube from a definite etched mark L" to the tap 



