APPLICATION OF ANALYSIS 63 



percentage of solids not fat, and give the same re- 

 action as cane sugar with resorcinol (p. 55), but by 

 Harrison's method no cane sugar is shown. 



Preservatives are detected in the same way as for 

 milk. For the estimation of boric acid, the cream 

 should be diluted with an equal weight of water. 



Adulteration of Skim-milk. The President of 

 the Board of Agriculture has fixed 9.0 per cent, as the 

 limit for total solids in skim-milk. Percentages below 

 this are presumed to be caused by the addition of 

 water. 



Rennet is sometimes added to skim-milk, and even to 

 whole milk, usually with the idea of causing curdling 

 when the milk is warmed. Its presence may be inferred 

 if the milk curdles on warming to 40 0., and the 

 acidity is less than 25 ; the whey on neutralising to 

 an acidity of 12 will cause fresh milk to curdle at 

 40, and the amount of lime in the whey does not 

 exceed 0.06 per cent. 



Detection of Foreign Fats in Milk and Cream. 

 By means of an emulsifying apparatus, foreign fats 

 (margarine fat, cocoa-nut oil) are mixed with separate 

 milk and the product sold as milk or cream. The casein 

 should be precipitated from a considerable amount of 

 milk (p. 35), dried, extracted with ether, and the fat-, 

 examined as butter fat (pp. 67 et seq.). 



