174 NORMAL MILK : ITS ADULTERATIONS, ETC. 



proposed the two following formulae, which hold good, not only 

 with normal milks, but with abnormal milks in addition : — 



'^ ~ ^^ ioo"=nF """"^"^^ ■^• 



G + F — 4L exceeds 16. 

 S = solids not fat, L = milk-sugar, F = fat, and G = lactometer degrees. 



Adulterations by Cane Sugar, &c. — Sometimes substances 

 such as cane sugar, dextrin, or other carbohydrates or glycerine 

 are added to mask the addition of water by raising the solids 

 not fat ; these will be detected by the sweet taste, the deficiency 

 in total nitrogen and the ash. Cane sugar, dextrin, etc., can 

 be detected by the discrepancy between the milk-sugar estimated 

 by polarisation and that determined by Fehling's solution (see 

 pp. 90 and 95). The detection and estimation of cane sugar is 

 ^iven on p. 101. 



Glycerine, if added to any appreciable extent, will render 

 the total solids sticky, and on analysing the sample the water, 

 fat, milk-sugar, proteins, and ash will in the aggregate be seriously 

 below 100 per cent. It can be detected, and approximately esti- 

 mated, by evaporating 25 c.c. of milk to a pasty consistency, 

 treating with a mixture of alcohol and ether, and following the 

 procedure of the maceration method of analysis ; the alcohol- 

 •ether extract is evaporated and the residue exhausted with a 

 httle water and this again evaporated. If glycerine be present, 

 a residue having a sticky consistency when cold will be left ; 

 the weight of this, less that of the ash left on ignition, wUl approxi- 

 mately give the amount of glycerine. 



Starch has also been used ; this is detecled by a blue color- 

 ation being obtained with a solution of iodine in potassium 

 iodide (see p. 106). 



Rennet is occasionally added to milk, aud more especially to 

 separated milk, with the idea that if mixed with warm milk it 

 will cause curdling. Its presence may be inferred if the milk 

 curdles on warming to 40° C, and the acidity is less than 25° ; 

 the whey' on neutralising to an acidity of 12° will cause fresh 

 milk to curdle at 40° C, and the amount of lime in the whey 

 does not exceed 0"06 per cent. 



Brains and mammary tissue are said to have been used; 

 this is doubtful, but they would be shown at once by the large 

 deposit obtained on centrifuging the milk. 



Mineral adulterants have been employed. The use of chalk, 

 which is popularly supposed to enter into the composition of 

 adulterated milk, is probably hypothetical, as its insolubility 

 would defeat the object of its use. Salt is detected in the ksh 



