328 Repoet of the Department of Chemistry of the 



higher amount of calcium is soluble in water, while the other is 

 insoluble. It will be later shown by us that both of these com- 

 pounds are soluble in pure water. In reporting the compound 

 neutral to litmus to be insoluble in water, the fact was overlooked 

 that, under the conditions of their experiments, there was always 

 present in the mixture a considerable amount of calcium chloride, 

 which was formed by the reaction of the hydrochloric acid upon the 

 lime-water solution of paracasein, and the presence of this calcium 

 chloride caused the precipitation of the neutral calcium paracaseinate, 

 as we shall show later. 



We have been able to prepare compounds of paracasein corre- 

 sponding to the mono- and di-basic caseinates, in which, however, 

 the proportion by weight of paracasein to base is just one-half that 

 found in the caseinates. 



PREPARATION AND COMPOSITION OF ASH-FREE PARACASEIN. 



Milk from which the fat has been removed as completely as pos- 

 sible by centrifugal force was heated to 37° C. and rennet-extract 

 (Hansen's) was added in the proportion of 0.12 cc. per 1,000 cc. of 

 milk. The milk was allowed to stand until the precipitated para- 

 caseinate had separated as completely as possible. The resulting 

 curd was then stirred vigorously in order to break it into small 

 pieces and hasten the separation of the whey. When the curd had 

 settled, the supernatant whey was removed by siphon. The para- 

 caseinate was washed Avith distilled water several times, and finally 

 5 liters of water were added for each liter of milk originally used. 

 Dilute ammonium hydroxide (6 cc. of strong reagent diluted to 

 1,000 cc.) was then added, as in the case of the preparation of casein 

 (p. 314), and the mixture stirred until the paracaseinate was dissolved. 

 The process of precipitating, washing and redissolving was con- 

 tinued as in the case of casein; the remaining calcium was finally 

 separated by addition of ammonium oxalate and centrifuging. One 

 preparation made in this way contained 0.07 per ct. of ash. One 

 gram gave a clear solution when dissolved in 10 cc. of ^ NH4 OH 

 and 90 cc. of water. One preparation, with high ash content, gave 

 the following results on analysis: 



Per ct. In dry substance: Per ct. 



Moisture 1.63 Nitrogen 15.80 



Ash 0.61 Phosphorus 0.83 



In dry substance: Sulphur 0. 87 



Carbon 53 . 50 Oxygen (by difference) 21 . 13 



Hydrogen 7 . 26 



Another preparation with exceptionally low ash content gave the 

 following results: 



Ash 0.07 per ct. Phosphorus. ... 0.71 per ct. Sulphur 0.72 per ct. 



