CHAPTER XIX 



THE CHEMICAL CONSTITUENTS OF MILK 



Ash. Average samples of genuine milk contain about 075 per 

 cent, of ash. The limits of variation are from 0*4 to 0*86 per 

 cent., but the extremes are reached only in abnormal samples. 



The ash is, of course, the non-volatile residue which 

 remains after incineration of the solids. It is often referred 

 to as the mineral matter, or inorganic constituents of the milk. 

 It is as truly organic as the proteins. Some of the elements 

 of which it is composed actually form part of these compounds 

 as they occur in milk. 



The ash exhibits a feeble alkaline reaction, and the slight 

 effervescence produced on treatment with acids, shows the 

 presence of a small amount of carbonates. Apart from carbon 

 dioxide and traces of unoxidised carbon, it consists of the 

 elements sodium, potassium, magnesium, calcium, iron, phos- 

 phorus, chlorine, sulphur, and oxygen. The chlorine is com- 

 bined chiefly with the alkalis. All the other elements are 

 present in combination with oxygen. Some of these oxides 

 are united together in the form of salts, e.g. sulphates and 

 phosphates. Quantitatively, the average composition is 

 approximately as follows : 



Per cent. 



Soda(Na 2 O) . , . . n 



Potash (K 2 O) ....<. , .... 26 



Magnesia (MgO) . . . v/ . , . . . 3 



Lime (CaO) 21 



Ferric oxide (Fe 2 O 3 ) .' . 0*4 



Sulphuric anhydride (SO 3 ) 4 



Phosphoric anhydride (P 2 O 5 ) 23 



Chlorine (Cl) 14 



Carbon dioxide (CO 2 ) 1-6 



Deduct oxygen equivalent to the chlorine . 



100-8 

 302 



