226 THE ANALYSIS OF SOLID MILK PRODUCTS. 



U.S. P. Tests for Dextrin and other Sugars. Add 20 c.c. 

 70 per cent, alcohol to 2 grammes in small bottle, place on a shaker 

 for half an hour, and filter. Place 10 c.c. of filtrate in a tared 

 beaker, add 10 c.c. absolute alcohol (solution should remain 

 clear indicating absence of dextrin), and evaporate on water- 

 bath, and weigh residue (not exceeding 0-03 gramme). 



The solution of 3 grammes -(- 10 c.c. water in a large test-tube 

 made by raising to boiling should be odourless, clear, and colour- 

 less, or, at most, faintly yellow. 



Fineness. Place 2 grammes on 120 mesh sieve. Shake gently 

 till no more passes through ; weigh residue. 



Weight x 50 = percentage over 120. 

 100 percentage over 120 = percentage through 120. 



Good commercial milk-sugar crystallised from water should 

 give the following figures : 



Milk-sugar per cent., . 99 -6 to 99*9. 



Birotation ratio, . . 1-6. 



Fall of temperature, . 0'5 C. 



Solubility at 15 C., . 7 - grammes per 100 c.c. (anhydrous sugar), 

 each 1 increase of temperature raises 

 this figure about - 1 gramme per 100 c.c. 



Ash, .... not more than 0'05 per cent. 



Milk-sugars which have been precipitated with alcohol usually 

 polarise slightly over 100 per cent. ; have a birotation ratio 

 below 1 -6 and, usually, above 1 -5 ; cause a slightly greater fall 

 of temperature ; and have rather a higher solubility in water. 



Detection of Adulteration. Milk-sugars which are adulter- 

 ated with other sugars will show marked divergence from the 

 above figures. Cane-sugar can be detected by treating a solution 

 with a little yeast and keeping at 55 C. for five hours ; milk- 

 sugar shows no change in specific rotatory power, while the 

 presence of even 1 per cent, of cane-sugar will produce a marked 

 alteration. 



Dextrose is detected by an increase in the birotation ratio, 

 by the solubility, and by a decrease in the fall of temperature. 



Maltose and dextrin (present in commercial starch-sugar) 

 are detected by a lowering of the birotation ratio, a great 

 increase in the apparent percentage of milk-sugar, and in the 

 solubility. 



Mineral adulterants will be easily detected by the high per- 

 centage of ash. 



