GENERAL CHEMISTRY OF MILK 101 



hygroscopic and dissolves in water with evolution of heat. By 

 rapid evaporation of a solution of milk-sugar in metallic vessels 

 the |8 modification is obtained. It has a lower rotation than the 

 a modification. 



The Mineral Constituents of Milk 



The mineral constituents of milk are usually given as ash, 

 obtained by first evaporating milk to dryness and then incinerat- 

 ing the residue at low red heat. A white ash is thus obtained 

 which has an alkaline reaction. Colostrum yields considerably 

 more ash than normal milk. The ash varies in the milk from dif- 

 ferent animals, as the following figures given by Trunz, who 

 quotes the work of several investigators, show: the ash of goat's 

 milk is 0.7 per cent.; of sheep's milk, 0.8 per cent.; of mare's 

 milk, 0.28 to 1.20 per cent.; of ass's milk, 0.30 to 0.40 per cent.; 

 of human milk, 0.19 to 0.34 per cent. 



The ash is composed of substances derived from organic and 

 inorganic compounds. Carbon, sulphur, and phosphorus are de- 

 rived in part from organic compounds. Therefore it is custom- 

 ary to speak of crude ash which contains all inorganic substances 

 contained in milk and of pure ash which contains only those sub- 

 stances which are present in milk in inorganic form. Pure ash, 

 therefore, is the crude ash from which the organic carbon, sul- 

 phur, and phosphorus have been deducted. 



The ash does not represent all the elements which constitute 

 the salts in milk, as some are lost by escaping during incineration. 



Carbon appears in ash as CO2, sulphur as SO3, and phosphorus 

 as PzOs. 



The elements found in the ash of milk are potassium, sodium, 

 calcium, magnesium, phosphorus, iron, sulphur, chlorin, hydrogen, 

 oxygen, and traces of fluorin, iodin, and silicon. Soldner has 

 given the following theoretic arrangement of these elements in 



AMOUNT AND PERCENTAGE OF SALTS IN MILK 



Compound. Per cent. Grams. 



Sodium chlorid 10.62 0.962 



Potassium chlorid 9.16 0.830 



Monopotassium phosphate 12 . 77 1 . 156 



Dipotassium phosphate 9 . 22 . 835 



Potassium citrate 5.47 0.495 



Dimagnesium phosphate 3.71 0.336 



Magnesium citrate 4.05 0.367 



Dicalcium phosphate 7.42 0.671 



Tricalcium phosphate 8.90 0.806 



Calcium citrate 23 . 55 2 . 133 



Calcium oxid (caseinate) 5.13 0.465 



In solution are the salts of potassium, sodium, chlorin, citric 

 acid, some phosphates, calcium salts, and magnesium salts.' Bl- 

 and triphosphates are in suspension and do not pass through a 



