SOME PHYSICO-CHEMICAL MEASUREMENTS ON MILK. 



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for five minutes and then cooling down. This points to 

 the fact that the change takes place in the non-conducting 

 constituents of the milk. 



It will also be noticed that before the change takes place, 

 which increases the time of flow, another change manifests 

 itself which has the effect of decreasing the time of flow, 

 so it would seem, that on heating milk two changes take 

 place, (1) a liquefaction, (2) a coagulation. 



The Electrical Conductivity of Milk. 

 Since the quality and the quantity of cow's milk is 

 influenced by so many factors, such as the breed of cow, 

 feeding, weather conditions, etc., it is to be expected that 

 considerable variations would occur in the conductivities 

 of different milks. The conducting constituents of a milk 

 are its soluble salts. The proportion in which the mineral 

 salts exist in milk is given by Soldner as follows: 



Sodium chloride ... ... 10'62 per cent. 



Potassium chloride ... ... 9*16 



Mono potassium phosphate ... 12*77 



Di-potassium phosphate ... 9*22 



Potassium citrate 5*47 



Di-magnesium phosphate ... 3*71 



Magnesium citrate ... ... 4*05 



Di-calcium phosphate... ... 7*42 



Tri-calcium phosphate ... 8*90 



Calcium citrate ... ... 23*55 



Lime combined with proteins 5*13 



It will be seen from the above analysis that the chlorides 

 and citrates comprise 52*85 per cent, of these salts, the 

 remainder being phosphates of which a great part is held 

 in suspension and thus can have little effect on the con- 

 ductivity. Potassium chloride has a specific conductivity 

 of 4*3 x 10~ 3 reciprocal ohms at 26° O., for an n/32 solution, 

 the value for the corresponding citrate is 2*2 x 10~~ 3 . A 



