220 MILK 



solution of ammonium molybdate and 8 c.c. hydrochloric acid 

 (1 part 25 per cent. HCl and 7 parts water). After shaking, heat 

 in a water-bath at 80° C. for five minutes. A blue color develops 

 when saccharose is present, and becomes more intense with pro- 

 longed heating. Normal milk develops a faint green color un- 

 less the temperatm-e is raised to boiling, when a blue color ap- 

 pears. 



Cane-sugar can also be detected by boiling 5 to 10 c.c. of the 

 milk with 0.1 gram resorcin and a few drops of hydrochloric acid 

 for a few minutes. A rose-red color develops in the presence of 

 cane-sugar. 



Richmond's method for detecting cane-sugar consists in de- 

 termining the polarization of the suspected milk as for milk-sugar. 

 The amount of milk-sugar is then determined by using FehUng's 

 solution. The difference between the amount of anhydrous milk- 

 sugar found and that resulting from dividing the polarization by 

 1.217 gives the percentage of cane-sugar present. 



The presence of gelatin is determined according to the follow- 

 ing method given by the Association of Official Agricultural 

 Chemists : 



" Prepare an acid solution of mercuric nitrate in twice its weight 

 of nitric acid of 1.42 specific gravity, and dilute this solution to 

 twenty-five times its bulk with water. To 10 c.c. of the milk 

 (or cream) to be examined add an equal volume of the acid mer- 

 curic nitrate solution, shake the mixture, add 20 c.c. of water and 

 shake again, allow to stand five minutes, and filter. If much 

 gelatin is present the filtrate will be opalescent and cannot be 

 obtained quite clear. To a portion of the filtrate contained in a 

 test-tube add an equal volume of a saturated aqueous solution 

 of picric acid. A yellow precipitate will be produced in presence 

 of any considerable amount of gelatin, while smaller amounts 

 will be indicated by cloudiness. In the absence of gelatin the 

 filtrate obtained will remain perfectly clear." 



There is no sanitary objection to the use of sucrate of lime or 

 gelatin, but their presence is a confession of some deficiency in 

 the quality of the milk unless the sucrate of lime is added to re- 

 store the viscosity lost through pasteurization. In this case the 

 addition should be stated on the bottle. But when such addition 

 is made to conceal the effects of tampering with the milk, its de- 

 tection is of importance. 



Addition of Foreign Fat to Milk, — If milk has been skimmed, 

 some foreign fat may be added to replace the amount of milk- 

 fat removed. By the use of homogenizing machines the fat may 

 be incorporated in the form of an emulsion, simulating the natural 

 emulsion of butter-fat. However, the globules formed by a homo- 



