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 asfollows: 10c.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. 
