214 



REPORTS OF INVESTIGATIONS AND PROJECTS. 



Silver perchlorate appears not to have been made the subject of an electro- 

 lytic investigation, though it is a very stable salt, before it was taken up 

 under this grant from the Carnegie Institution. Numerous depositions of 

 silver have been made with two coulometers in series, usually one with a 

 nitrate solution and the other with a solution of the perchlorate of silver. 

 Silver perchlorate is not an article of commerce, and it had therefore to be 

 prepared. (For the method, see Trans. Amer. Electrochemical Soc, vol. ix, 



p. 375. 1906.) 



Two conclusions may be drawn from these comparison experiments. First, 

 no evidence has been found confirming Professor Richards' theory. The 

 results are the same whether the anode is contained in a porous cup, or is 

 surrounded, without touching, by a hard quality of filter paper. Second, the 

 perchlorate gives results slightly more uniform than the nitrate, and the silver 

 deposited from the former adheres more firmly than that from the latter. 

 Hence the liability of loss in washing is less with the perchlorate than with 

 the nitrate. 



Three determinations of the electrochemical equivalent of silver have been 

 made in terms of the electromotive force of the Weston cell. The current 

 was measured by comparing the fall of potential over two standard ohms in 

 series with the electromotive force of a Weston cell by means of a Wolff's 

 potentiometer. The deposition of silver continued in each case for one hour, 

 and a balance was taken about every minute. When the fall of potential was 

 plotted as ordinates and the times as abscissas, the result was a very satis- 

 factory smooth curve. This curve gave the number of coulombs for com- 

 parison with the weight of silver deposited in each cup, one containing a solu- 

 tion of silver nitrate and the other a solution of silver perchlorate. 



The following are the results on the basis of i. 01 867 volts at 20° C. for 

 the Weston cell set up with mercurous sulphate prepared by precipitation, as 

 reported a year ago (Year Book No. 5, 1906, p. 227) : 



The mean values represent the electrochemical equivalent of silver in 

 grams per coulomb, obtained by means of the absolute electrodynamometer 

 through a Weston cell. 



The major part of this work has been ably carried out by my associate, Dr. 

 W. D. Henderson. 



