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 10 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- 



