Xkw Yokk Agricultukal Experiment Station. 



329 



preparation and composition of basic calcium para casein ate. 

 Like casein, paracasein manifests its acid character by its power 

 to liberate carbon dioxide from calcium carbonate, forming a calcium 

 paracaseinate. The results of the reaction were measured by us in 

 the same manner as in the case of casein (p. 316), and it is, therefore, 

 not necessary to report any of the details of methods or results. 

 The average of many determinations indicates that paracasein 

 unites with calcium to form a paracaseinate which is neutral to 

 phenolphthalein and has the same general composition; 1 gram of 

 paracasein combines with 9 x 10* gram equivalents of calcium. 



preparation and composition of unsaturated or acid 



paracaseinates. 



In preparing acid paracaseinates of bases, the same volumetric 

 method of procedure was followed as in case of the casein salts 

 (p. 318). The appearance of a precipitate in a centrifuged portion 

 after addition of acid to an alkali solution of paracaseinate was 

 made to serve as an indicator in regard to the end point of the reaction. 

 We dissolved 5 grams of the ash-free paracaseinate in 200 cc. of ^ 

 alkali, made up the solution to 250 cc. and then determined the end 

 points by careful addition of ^ HCl to 50 cc. portions. 



Acid paracaseinates of ammonium, sodium and potassium. — In the 

 manner described, determinations were made in the case of base- 

 free paracasein dissolved in hydroxide of ammonium, sodium and 

 potassium, with the results tabulated below: 



Table X. — Relation of Alkali Bases to Paracasein in Acid Paracaseinates. 



These results show that 1 gram of paracasein combines with an 

 amount of alkali somewhere between 2.2 x 10* and 2.3 x 10* gram 

 equivalents, in forming soluble compounds with ammonium, sodium 

 and potassium, which are acid to both litmus and phenolphthalein. 

 Expressed in another form, 1 cc. of jq alkali combines with an amount 

 of paracasein somewhere between 0.435 and 0.455 gram. The 

 proportion of basic element in each compound is approximately as 

 follows: NH4, 0.40 per ct.; Na, 0.52 per ct.; K, 0.88 per ct. The 

 amount of each basic element in these paracaseinates is just double 

 that present in the corresponding casein compounds (p. 320). 



