262 



THE CHEMICAL CONTROL OF THE DAIRY. 



There are 0-675 equivalent of lime and 0-325 equivalent of 

 magnesia to 1-506 equivalents of phosptoric anhydride, showing 

 that the insoluble ash consists chiefly of (Ca, Mg) (Na, K) PO^ 

 like the insoluble ash of milk. 



The quantity of separator slime amounts to about 0-04 part to 

 100 parts of milk separated, and varies within comparatively 

 narrow limits — 0-02 to 0-08 — unless the milk is very dirty, when 

 it may even reach 0-15 ; in a sample where the last figure was 

 reached the slime was brown and very gritty. 



It has been argued that the removal of the slime purifies the 

 milk to such an extent that its keeping qualities are enhanced. 

 This opinion is probably founded on observations of the number 

 of microbes contained in the slime ; but though a greater relative 

 quantity are found than in the milk, the numbers left in the 

 cream and separated milk are not appreciably diminished. 



Fig. 35. — Diagrammatic Section of Separators. 



Practice has, however, shown that a mixture of cream and 

 separated milk in their original proportions keeps no better 

 than the milk from which they were separated. 



Micro-organisms are so small that their separation, unless 

 carried with much larger solid particles, would be almost im- 

 possible under the conditions of the separation of cream ; in 

 addition, many of them have a density less than that of milk 

 serum. 



The author found 



Top, . . 197,000 colonies per c.c. Growth on gelatine at 22° rapid, 



about 20 per cent, liquefied. 



Middle, . 5,000 



Bottom, . 194,000 „ Growth on gelatine slow, none 



liquefied. 



