RICHARDS AND HEIMROD. — THE IMPROVED VOLTAMETER. 



435 



On the other hand, the deposit, in common with most crystals, may 

 retain small quantities of solution or wash-water. Lord Rayleigh seems 

 to be the only one who has taken this possible source of error into ac- 

 count. He heated the crucibles to incipient redness, after they had been 

 dried at 130° to 1G0°, and weigbed. A loss of about .014 per cent 

 was thus found. Richards and Collins, in looking for an explanation 

 of the cause of discrepancies in the atomic weight of copper, had 

 found by analysis the silver deposit to contain about 0.01 per cent of 

 impurity. 



For our purpose the direct method of Lord Rayleigh seemed better 

 than the indirect analytical one. The deposits, which had been dried 

 thoroughly at 160° and weighed, were heated over an alcohol lamp to 

 constant weight. Care was taken to heat the whole crucible evenly, and 

 to use as high a temperature as possible without the formation of an 



TABLE XII. 

 Loss OF Weight of Silver Deposits ^on heating. 



