ELECTROLYSIS 



179 



in the percentage-content of casein, divided by 4, was the amount 

 of casein precipitated by the current. 



The experiments were all conducted at 30° C. 



Varying amounts of casein were dissolved in 100 cc. each of 

 KOH solutions of varying concentrations so that the proportion 

 of base to casein was 50 X 10~^ equivalents per gram (neutral 

 to litmus),* or 80 X 10~^ equivalents per gram (neutral to phenol- 

 phthalein),t or 100 X 10~^ equivalents per gram. In estimating 

 the current employed, the electrochemical equivalent of silver, 

 in grams per coulomb, is taken as 0.001118 (8). 



It was found that the solutions containing the higher pro- 

 portions of base to casein jaelded an apparently lower electro- 

 chemical equivalent for the casein. This was speedily traced to 

 resolution of the casein from the electrode after precipitation. 

 The anode, after having been coated with casein by the action 

 of a current of one milliampere passing through a 3 per cent 

 solution of casein, neutral to litmus, was washed in water, alcohol 

 and ether, dried and weighed. It was then immersed in a solu- 

 tion of casein (3 per cent) neutral to litmus for 2 hours, then 

 withdrawn and washed, dried and weighed as before. It was 

 found to have lost 11 milligrams in weight. Similar experiments 

 were conducted in which the solutions in which the coated wire 

 was immersed were neutral to phenolphthalein and alkaline to 

 phenolphthalein. The following were the results obtained: 



Hence doubling the rate of deposition makes very little, if 

 any, difference to the rate of resolution of the casein, but increas- 

 ing alkalinity of the solution in which the deposition occurs 

 increases the rate of resolution very markedly. J 



* Cf. Chap. V. Also T. Brailsford Robertson (27). 



t Cf. Chap. V. 



t If the anode be much less than 9 cm. in length there is a tendency, after 

 prolonged electrolysis, to what may be termed "fiocculent deposition," or 

 precipitation of the casein within the body of the fluid in the anodal arm and 



