46 MILK 



Gelatin produces a yellow precipitate. Picric acid 

 will detect the presence of i part of gelatin in 

 10,000 parts of water. The picric acid solution 

 should not give a precipitate with the nitrate 

 solution. 



For sucrose Cotton devised the following tests : 

 10 c.c. of the sample are mixed with 0.5 gram 

 of powdered ammonium molybdate, and 10 c.c. 

 of dilute hydrochloric acid (i to 10) are added. 

 In a second tube, 10 c.c. of pure milk or 10 c.c. 

 of a 6 % solution of lactose are similarly treated. 

 The tubes are then placed in the water-bath and 

 the temperature gradually raised to about 80°. 

 If sucrose is present, the milk will become blue, 

 while genuine milk or milk-sugar remains un- 

 altered unless the temperature is raised to the 

 boiling-point. According to Cotton, the reaction 

 is well marked in the presence of as little as i 

 gram of sucrose to 1000 c.c. of the milk. For 

 the detection of other organic thickening agents, 

 such as pectoses, agar and mixtures of agar and 

 gelatin, see under "Cream," page 67. 



Calcium Saccharate (Saccharate of Lime). — ^A 

 compound produced by the action of lime on 

 sucrose has been used as a thickening agent. A 

 test due to Bauer and Neumann is recommended 

 by Lythgoe, from whose description the following 

 is taken : 



To 25 c.c. of milk (or cream) add 10 c.c. of 



