338 Repokt of the Departmext of CiiEMisTin-. 



2.25 X 10"* gram equivalents of calcium. Indications pointed to the 

 identity of the brine-soluble compound of cheese with this mono- 

 calcium paracaseinate, and it remained to ascertain whether the 

 protein part of the molecule in these two compounds is the same. 

 In order to accomplish this, a preparation of the protein in the 

 brine-soluble compound was made from cheese and its composition 

 and properties were studied. 



One kilogram of cheddar cheese was ground fine and then extracted 

 with numerous portions of distilled water at about 55° C. in order 

 to remove all soluble compounds. The residue was then extracted 

 with many portions of a 5 per ct. solution of sodium chloride and 

 filtered, first through absorbent cotton and then through paper. 

 Dilute acetic acid was then added, giving a heavy precipitate, which 

 was washed with water, redissolved in dilute ammonia and again 

 precipitated with acid. The process was then completed as in the 

 preparation of casein (p. 315). The preparation on analysis gave the 

 following results, which are probably high, owing to the ash content: 



Per ct. In dry substance: Per ct. 



Moisture 2.32 Nitrogen 15.82 



Ash 0.25 Phosphorus 0.75 



In dry substance: Sulphur . 78 



Carbon 52.97 Oxygen (by difference) 22.28 



Hydrogen 7 . 15 



A study of the properties of this substance resulted as follows: 



(1) The substance acts as an acid in combining with bases. 



(2) It decomposes calcium carbonate and gives a compound in 

 which 100 grams of substance combines with the equivalent of 2.52 

 grams CaO (equal to 1.80 grams Ca), or 1 gram of substance com- 

 bines with 9 X 10* gram equivalents of calcium. 



(3) The solution of this calcium compound is neutral to 

 phenolphthalein. 



(4) Measured by the volumetric method, it was found to form a 

 compound with ammonia represented by the combination of 1 gram 

 of substance with 2.3 x 10'* gram equivalents. 



(5) With calcium it forms a compound soluble in 5 per ct. solution 

 of sodium chloride but insoluble in water, which contains 1 gram of 

 substance combined with 2.3 x 10* gram equivalents of calcium. 



(6) It forms also a compound with calcium that is soluble in water, 

 containing 1 gram of substance combined with 4.5x10"* gram 

 equivalents. 



In view of the marked agreement of the composition and prop- 

 erties of the brine-soluble substance, formed in cheese, with the 

 compound, mono-calcium paracaseinate, as prepared by us, there is 

 good reason to believe that the brine-soluble substance is mono- 

 calcium paracaseinate, having the composition of 1 gram of para- 

 casein combined with 2.25 x 10* gram equivalents of calcium. 



