ON THE SILVER VOLTAMETER. 555 



It is of interest to state that the diminution in mass of these four bowls from 

 June, 1906, to June, 1907, is 0'8 milligram only. The electrical method of removing 

 the deposit from the bowl does not take the platinum into solution, and the mass of 

 any one bowl in a series of five or six experiments remains constant to O'l milli- 

 gramme. We observed this constancy and found it a most useful check on our 

 weighings of the empty vessels. 



As the results of our observations differ very materially from those of nearly all 

 other workers on the same subject, we include particulars of the kathode, anode, 

 solution, current and deposit in Table I. These results are in chronological order and 

 include the measurements discussed in Part II. of this paper. 



When two or more voltameters were placed in series and the same current primed 

 through each, the results of the observations are indicated by the same number, but 

 by different letters. For those observations in which the current was maintained 

 steady throughout the time of the deposit, the value of the current in amperes 

 (10~ ! C.G.S. unit) is stated to 1 part in 1,000,000. This is for the accurate com- 

 parison of results ; the error of this measure is about 2 parts in 100,000. The time 

 is recorded to one-hundredth of a second and is probably correct to O'l second. When 

 the observations were made merely for the comparison of different forms of volta- 

 meters and the current was not maintained steady, the approximate value of the 

 current only is given. Except in four special cases (43a, b, c, d) the electrochemical 

 rijiiivalent is calculated to 1 part in 100,000. 



Under the heading of solution, letters are given which indicate the source of the 

 silver nitrate crystals ; H, M, G, and W are samples of silver nitrate purchased 

 from four different manufacturing chemists, and when more than one sample was 

 purchased from the same firm a number accompanies the letter. LR indicates that 

 the salt was recrystallised by LOWRY, and SR that the same process was conducted 

 by SMITH. WS is a solution from Professor WATSON, and the VD solutions were 

 prepared from salt recrystallised by. Professor VAN DIJK. The degree of electrolysis 

 of the solution, i.e., the ratio of the silver previously deposited by the passage 

 of an electric current through the solution to that present in the solution is stated 

 in column 8, and some brief notes on the appearance of the deposits appear in the 

 last column. The pressure to which the electrolyte was subjected and its temperature 

 are also stated, but only when these differed from the pressure and temperature of the 

 air of the room in which the observations were made. 



In column 4, R denotes the Rayleigh form of voltameter, P the Richards (porous 

 pot) form, S the syphon form, P.S.B. and S.P.B. the arrangements we have called the 

 pot-syphon-bowl, and syphon- pot-bowl forms, respectively, and EL.K. the elevated 

 kathode form. 



4 B 2 



