THE VKLOCITV OK DISSOLUTION OF MOLECI'LAR LAYERS 93 



Table 3 



ll is also evident thai in the presence of a reducing agent sucii as 

 oxalic acid the large difference between the dissolution velocities of the 

 (•atliodically and anodically deposited lead isotopes disappears, in 

 agreement with the ready solubility of the peroxide in oxalic acid solution. 



In the more recent development of electrochemistry particular atten- 

 tion is devoted to the reactions wdiich take place between the deposited 

 products and the electrode material ; the study of the velocity of 

 solubility with the elect rolytically deposited radioelements offers an 

 easy method of approaching more closely to these problems ; thus, in 

 the case of polonium it was proved that this element forms stable com- 

 ])ounds more easily with Pt and Pd than with gold. 



Change in the Dissolution Velocity due to the Presence of Isotopic Ions 

 of the Dissolving Metal in the Solution 



Isotopic atoms are interchangeable in their electrochemical reactions^ 

 Now the dissolution of a metal is to some extent the reverse of its electro- 

 lytic deposition and therefore it is to be expected thatThB will dissolve 

 only to the same small extent as lead in nitric acid saturated with lead 

 nil rate. 



Before discussing the behaviour of a molecular layer when dissolving 

 in a solution which already contains some dissolved isotope, we w^ould 

 like first to explain in more detail the process which takes place between 

 a solid phase and its saturated solution. Just as the equilibrium state 

 between a liquid and its saturated vapour is regarded as dynamic, i.e. 

 the assumption is made that the same number of molecules condense 

 from the vapour and leave the liquid in unit time, the equilibrium state 

 between a solid phase and its saturated solution is also regarded as 

 dynamic, i.e. it is assumed that at the boundary of, for example, 



PbC'lg solid I water saturated with PbC'lg 



a dynamic exchange of PbClg molecules takes place between the two 



iG. Hevesy hihI F. Paneth, Phy-s. Z. 15, 7!J7 (1914). 



