DETECTION OF ADULTERATION 63 
mercuric nitrate described on page 37. In 
the presence of abrastol a distinct yellow tint is 
produced in a few minutes. Greater delicacy 
can be obtained by using the same proportion 
of the reagent with 10 c.c. of milk known to be 
pure. 
Organic Contamination.—Sanitary control of 
market-milk also involves tests for animal prod- 
ucts, such as pus cells, and the identification 
of specific microbes, such as those causing tuber- 
culosis and typhoid fever. These investiga- 
tions, however, are mostly outside of the scope 
of a work on chemical analysis. For informa- 
tion concerning these recourse must be had to 
works on pathology and bacteriology. 
Several chemical tests have been published 
by which it is claimed that approximate deter- 
mination of these contaminating organisms and 
substances can be made but they are not capable 
of replacing the exact methods of the pathologic 
and bacteriologic laboratory. One of these is 
the following. A dilute solution of methylene 
blue is prepared by adding 5 c.c. of a saturated 
alcoholic solution of the dye to 200 c.c. of water. 
0.5 c.c. of this solution is added to ro c.c. of 
the sample. If the color is discharged promptly, 
the sample contains over 100,000,000 bacteria 
per c.c. 
Hydrogen dioxid has been shown by the in- 
