HARPER F. ZOLLER 647 



as one of racemization or a keto-enolic tautomerism. Whatever 

 explanation might serve to describe the change taking place in the 

 molecule to effect the optical properties, there is a far greater funda- 

 mental change taking place in the casein molecule in the presence of 

 these concentrations of alkalies which has received little attention. 

 Maynard^^ has shown that NaOH of 2 per cent concentration also 

 cleaves loosely combined sulfur from the casein molecule, a fact 

 apparently noted by Dakin and Dudley.^^ 



The writer has been able to prepare an acid-precipitable product, 

 from the action of 2 per cent NaOH upon casein, that contains no 

 sulfur, no nitrogen in the free amino form, and only a trace of phos- 

 phorus. The action of the alkali upon the casein proceeded for 6 

 days at 30°C. The gelatinous solution was diluted with water and 

 treated with dilute acetic acid. The curd or precipitate was col- 

 lected and thoroughly washed with water containing a trace of acetic 

 acid. It was then thoroughly washed with distilled water and dried 

 to constant weight, and analyzed for amino nitrogen, sulfur, and 

 phosphorus. The action of alkali upon the casein has been more 

 severe than a racemization or enolization, and it is quite likely that 

 the loss of amino nitrogen, sulfur, and phosphorus from the casein 

 molecule is partially responsible for the decline in rotation observed 

 by Dakin and his coworkers. 



In applying this knowledge to the explanation of the flattening of 

 the viscosity curves in the alkaline zone the writer has found that the 

 cleavage of sulfur and phosphorus is simultaneous with the cleavage 

 of amino nitrogen. They both commence at nearly the same inten- 

 sity of hydroxyl ion concentration, or, reciprocally, at about the same 

 pH (10.0 to 10.5). The hydrolysis also commences as soon as the 

 casein is dissolved in solvent at this pH. Within 6 hours nearly ^ 

 the phosphorus and sulfur had been cleaved from the casein at pH 

 11.1 (9 per cent casein solution). When a few drops of CUSO4 solu- 

 tion are added to the flasks containing solutions of casein for viscosity 

 measurements, it is observed that the characteristic biuret color 

 develops within a few minutes in those solutions which are found to 

 evolve ammonia, and the depth of violet color increases with time and 



^^ Maynard, L. A., /. Physical Chem., 1919, xxiii, 145, 



