CANE SUGAR, ETC. 215 



The test may be performed in a nitrometer or other measuring 

 apparatus, and the volume of the gas measured. 



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. 154 and 159). 

 The detection and estimation of cane sugar is given on p. 165. 



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 in the aggregate will be seriously 

 below 100 per cent. It can be detected, and estimated approxi- 

 mately, 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 

 little water and this evaporated again. 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, will approxi- 

 mate to the amount of glycerine. 



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

 ation being obtained with a solution of iodine in potassium 

 iodide (see p. 170). 



Rennet occasionally is added to milk, and 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 

 will 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 

 deposits obtained on centrifuging the milk. 



Mineral adulterants have been employed. The use of chalk, 

 which is supposed popularly 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 ash 

 by an increase in the chlorides above 0-10 per cent., or it may 

 be estimated as described under Buttermilk (q.v.) ; an estimation 

 of sodium should also be made, as milk does not contain more 

 than 0-05 per cent. ; carbonate or bicarbonate of soda is also 

 detected by the increased alkalinity of the soluble ash ; this 

 does not exceed in genuine milk an amount equal to 0-025 per 

 cent. Na 2 C0 3 ; an amount exceeding this appreciably is due to 



