28 SCIENCE AND PRACTICE OF DAIRYING. 



of phosphoric acid (P 2 O 5 ). Milk containing the average percentage 

 of ash, viz. '75 per cent, and the average percentage of casein, viz. 

 3*2 per cent, contains, therefore, in its ash, "062 per cent of phos- 

 phoric acid. Of this '062 per cent, about 8 per cent is derived from 

 the phosphorus in the casein. In order, therefore, to find the 

 quantity of phosphoric acid which is present as such in milk, 8 per 

 cent has to be deducted from that found in the ash, which is, on an 

 average, 2 7 '5 per cent of the total ash. 



If this be done, and carbonic acid be deducted as well as the 

 sulphuric acid, and the small quantity of carbon present, the follow- 

 ing results, when the remaining portion is calculated to percentage 

 and the metals reckoned as oxides, are obtained, from which the 

 average percentage of the different mineral constituents of milk 

 may be seen: 



Potassium oxide, 25-64 



Sodium oxide, ... ... ... ... 12-45 



Calcium oxide, ... ... ... ... 24-58 



Magnesium oxide, 3-09 



Ferric oxide, ... ... ... . . ... 34 



Phosphoric acid, ... ... ... ... 21 '24 



Chlorine, 16-34 



103-68 

 Deduct oxygen for chlorine, 3-68 



100-00 



If we examine these figures more particularly, it will be found 

 that the chlorine (which without doubt is entirely combined with 

 the alkali metals) and the phosphoric acid, do not suffice to convert 

 the bases present into soluble salts possessing neutral or amphoteric 

 reaction, and that a large quantity of free calcium oxide remains 

 over. Even when we reckon that the casein, which plays the part 

 of an acid, forms a soluble compound with the lime, and that accord- 

 ing to Soldner this compound consists of 100 parts of casein and 

 1*55 parts of calcium oxide, there is yet an excess of the latter. Since 

 the carbonic acid which may be present in fresh milk in a state of 

 chemical combination is far short of being sufficient for effecting 

 neutralization, and since lactic acid is not present in fresh milk, it 

 necessarily follows that other acids organic acids are present in 

 the milk and conduce to bring about this amphoteric reaction. 



