io MILK AND DAIRY PRODUCTS PART 



The lactic acid formed in this way precipitates the casein 

 of the milk, a process which is so familiar in the ordinary 

 souring of milk. 



Milk sugar reduces an alkaline copper solution (Fehling's 

 solution) on warming, and with bases forms saccharates which 

 can be precipitated from their aqueous solutions by alcohol. 

 The mineral salts of milk, which can be obtained by carefully 

 reducing milk to ash, consist of compounds of potassium, sodium, 

 calcium, magnesium, and iron, with phosphoric, sulphuric, and 

 carbonic acids. It is to be noticed, though, that undoubtedly 

 the carbonic acid is formed from the organic constituents of the 

 milk during the combustion, and in the same way the sulphuric 

 acid may be regarded as a decomposition product of the protein 

 of the milk. 1 



Further, in calculating the amount of phosphoric acid, the 

 phosphorus in the casein must not be forgotten, for, as has been 

 seen, this constitutes 0'85 per cent, of the casein. 



If the carbon dioxide, the sulphuric acid, and part of the 

 phosphoric acid are deducted, the following average composition 

 for the ash of milk is obtained, the metals being calculated as 

 oxides : 2 



K 25-71 per cent. 



Na 2 O 11-92 



CaO 24-68 



MgO 3-12 



Fe. 2 0. { 0-31 



tA 21-57 



Cl ., 16-38 



103 '69 per cent. 

 After deducting the O equi- 

 valent to Cl 3-69 



100-00 per cent. 



A consideration of the above figures shows at once that the 

 chlorine and the phosphoric acid are not nearly sufficient to 

 combine with all the bases. Even when it is borne in mind 

 that a certain quantity of the lime was in combination with 

 the casein, there is still a considerable excess, for the chlorine 

 and phosphoric acid are, without doubt, combined with the 



1 According to Steinegger and Allemann (Landw. Jahrb. d. Schiveiz, 1905, 

 Vol. VIII), H 2 S0 4 is found in milk to the extent of 0-0823-0-1311 g. per 

 litre. 



' 2 Fleischmann, Lehrbuch der Milchwirttchaft. Fourth Edition. Leipsic, 

 1907, p. 56. 



