698 



Transactions. — Chemistry. 



it will be seen that these values differ considerably, gradually 

 decreasing as the concentration increases. Therefore, in more 

 concentrated solutions there is less metal dissolved than the 

 amount of oxygen in solution appears to demand. This points 

 to some retarding action on the motion of the molecules. It 

 seemed probable that viscosity has such a retarding action on 

 the motion of the oxygen molecules in solution, reducing their 

 velocity, and consequently diminishing the number of impacts 

 on the surfaces of the plates in a given time, and so decreasing 

 the amount of gold dissolved. In order to test the validity of 

 this conclusion, the rates of solution of gold were determined 

 in cyanide solutions rendered more viscous by the addition of 

 various substances, such as sugar and glycerol, which might 

 be assumed to exert no chemical influence on the solubility of 

 the metal. The results are shown in Table III. : — 



Table III. 



These results prove very conclusively that the assumption 

 in regard to the retarding action of viscosity was correct. 



Suppose now that we consider the number of times in a 

 second a given oxygen molecule strikes a surface. We may 

 assume from the results just given that this will depend 

 on the viscosity coefficient z, or, in other words, will be a 

 function of z. So that, if N be the number, we can write 

 N = a + 6^ + c^^ + &c., where a, h, and c are independent of z 

 (Maclaurin's theorem) ; or, since Au/0 is dependent upon the 

 number of impacts in unit of time, we can write Au/0 — a -\- 

 hz + cz^ + &c. In order to ascei-tain if these relations hold 

 good for the values of Au and O found, I determined the 

 coefficients of viscosity of a number of cyanide solutions. The 

 observations were made by Gartenmeister's method (Zeit, 

 Physik. Chem., vi., 524), using Finkener's formula — 



_ rV^j vs 



Wv 8^ ■ 



