THE VELOCITY OV DISSOLUTION OF MOLECULAIl LAYERS 



91 



Tablk 1. — A^vioTN'Ts Dissoi.vKn IX ()0 sec 



The velocity of dissolution is the same in 10~* N acid as in conductivity 

 water but increases with further increase of the acid concentration and 

 in N acid amounts to about twice the above value. It is well known 

 that the bismuth isotopes dissolve colloidally in water and from diffusion 

 experiments the conclusion was drawn that this is no longer the case 

 in 10~3 N acid^. It suggests itself to associate the sudden increase in 

 Ihe velocity of dissolution with this change. 



The velocity of dissolution of finite layers depends on, among other 

 factors, the diffusion velocity of the products involved. In order to 

 change this velocity glycerol was added to the nitric acid in order to 

 cause a considerable increase of the viscosity and a corresponding lower- 

 ing of the diffusibility of the hydrogen and other ions without otherwise 

 changing the experimental conditions. The consequence of the glycerol 

 addition was. as is clear from Table 2, a decrease in the velocity of 

 dissolution. 



Table 2 



Dissolved in 

 K)-' N HXO, 



Dissolved in 10— ^X 



HXOj containing 



25% glycerol 



The viscosity of the glycerol mixture found by the ordinary outflow 

 method was 1.650 relative to that of water as unity. 



Even after treatment for several hours with concentrated acids it is 

 found that the quartz disk still retains about 20 per cent of its original 

 ThB— ThC coating which, however, is not present on the surface but is 

 situated inside the quartz where it has arrived through the so-called 



^ F. PA>rETH, 



(1913). 



Kolloid-Z. 13, 1, 297 (1913); G. Hrvp:.sy, Phys. Z. 14, I2U9 



