302 Report of the Department of Chemistry of the 



Phosphorus content of casein preparations treated in different ways. 

 In order to study the effect of treating casein in different ways 

 upon the content of phosphorus, and especially to ascertain what 

 effect partial hydrolysis may have upon the phosphorus content 

 of casein preparations, two preparations of casein were made and 

 each of these was treated in the manner described below. 



Preparation A was made in the usual way, treating alternately 

 with dilute acetic acid and ammonia, avoiding an excess of each 

 reagent. This preparation contained 0.857 per ct. of phosphorus. 



Preparation B was made according to the method given in a 

 previous paper, 7 the distinctive feature of which is treatment of 

 a solution of casein in dilute alkali with ammonium oxalate and 

 excess of alkali. This preparation contained 0.711 per ct. of phos- 

 phorus. 



(1) Treatment with excess of ammonia. Each of preparations 

 A and B (20 grams) was dissolved in dilute NH 4 OH and an excess 

 of the same reagent was added; after standing twelve hours at 

 37° C, the solution was centrifugalized and filtered, the casein 

 in the filtrate being then precipitated with dilute acetic acid. 

 This precipitated casein was washed, redissolved, reprecipitated 

 and finally washed with water, alcohol and ether. 



In the case of preparation A, the yield was 14 grams, contain- 

 ing 0.841 per ct. of phosphorus; in the case of preparation B, the 

 yield was 15 grams and the phosphorus content 0.713 per ct. 



The decreased yield in each case was due in part to hydrolysis 

 of casein and in part to mechanical losses. It is evident that 

 partial hydrolysis of casein preparations has no effect on the per- 

 centage of phosphorus in the unhydrolyzed casein that is recovered. 



(2) Treatment with ammonium oxalate and excess of ammonia. 

 Each of preparations A and B (20 grams) was dissolved in dilute 

 NH 4 OH and then ammonium oxalate and an excess of NH 4 OH 

 added, the mixture being allowed to stand twelve hours at 37° C. 

 The casein was separated as before. 



In the case of preparation A, the yield was 14 grams, contain- 

 ing 0.723 per ct. of phosphorus; in the case of preparation B, the 

 yield was 14.5 grams, containing 0.71 per ct. of phosphorus. 



In these two experiments, hydrolysis of casein by alkali has no 

 effect upon the percentage of phosphorus in the casein finally re- 

 covered. In the case of preparation A, the phosphorus content is 

 reduced from 0.857 to 0.723 per ct., as a result of the removal of 

 calcium phosphate from the casein preparation. In the case of 

 preparation B, the phosphorus content remains the same as in the 

 original preparation, because the casein used had already been 

 subjected to treatment with ammonium oxalate and excess of 



7 Loc. cit. 



