240 



Journal of the Asiatic Society of Bengal. [June, 1914.] 



of about 600 c.c. of air in or out of the case, and this, if saturated, 

 would carry about 002 gm. of water with it. In course of time 

 the sulphuric acid would become too dilute to exert any influence 

 on the insulation. It is evident from the diagrams that this 

 actually takes place. About twenty-four hours after fresh acid 

 has been introduced and the case sealed, the insulation com- 

 mences to deteriorate, and in damp weather it would be neces- 

 sary to reopen the case after about a month in order to 

 renew the acid. 



It would of course be easy to make arrangements to renew 

 the acid without opening the case. As we wish to test the effect 

 of more powerful desiccators than sulphuric acid, such as phos- 

 phorus pentoxide (or metallic sodium), we think that it would be 

 better either to make the case absolutely airtight, or to allow 

 the free circulation of air to continue, whilst ensuring that any 

 air which enters the case is thoroughly dried. By passing the 

 threads through small U tubes containing mercury, direct com- 

 munication with moist air can be prevented. This point is 

 now under investigation. 



