DETECTION OF ADULTERATION 45 



India buffalo. He states that one observer 

 has found that a depression to 0.537° indicates 

 2-3% of added water. The procedure requires 

 special apparatus and careful manipulation; data 

 from testing samples of known composition should 

 be obtained before relying on it in important 

 cases. 



Thickening Agents. — ^To conceal skimming 

 and watering many thickening agents have 

 been used. At least two instances of the use 

 of brain matter have been reported. Dextrin, 

 starch, sugar, salt, gelatin and agar have all 

 been used. 



Brain matter can be easily detected by the 

 microscope, starch jelly by the iodin test, 

 dextrin by increased polarimetric reading, sodium 

 chlorid by the increased chlorids in the ash. 

 Agar is frequently used in certain milk products, 

 especially the cheap ice-cream sold in American 

 cities. 



Gelatin. — Stokes detects the presence of gelatin 

 in cream or milk as follows : 10 c.c. of the sample, 

 20 c.c. of cold water, and 10 c.c. of acid mercuric 

 nitrate solution (page 37) are mixed, shaken 

 vigorously, allowed to stand for five minutes, 

 and filtered. If much gelatin is present, it may 

 be difficult to get a clear filtrate. A portion 

 of the filtrate is mixed with an equal bulk 

 of saturated aqueous solution of picric acid. 



