HYDROGEN DIOXIDE MILK TEST 1 29 



important problems to be undertaken. It is evident that the con- 

 trol exercised by the health authorities, while it has accomplished 

 much, is not sufficiently stringent or far-reaching to stamp out 

 tuberculosis in cows. 



A milk test much used in Holland and other European countries 

 is to ascertain the amount of gas formation in a unit of time, in a 

 fermentation tube containing a mixture of definite quantities of 

 milk and hydrogen dioxide. The amount of gas liberated is di- 

 rectly proportional to the amount of organic matter (bacteria, 

 body cells and other organic impurities) present. Tests made in 

 the laboratories of the CaUfornia College of Pharmacy and in the 

 laboratories of the San Francisco Board of Health would indicate 

 that the method gives uniform results and that such a method 

 would prove a most valuable addition to the routine milk examina- 

 tion, serving as a check and confirmation of the bacterial and body 

 cell counts. In order that the test may yield uniform results in all 

 laboratories, a uniform method of procedure must be adopted. 

 The following tentative method is suggested. 



A standard lo percent, volume (of available oxygen) solution of 

 hydrogen dioxide should be used. The peroxide should be standard- 

 ized to the specified quality. For determining the valuation of the 

 peroxide we would recommend the Planes colorimetric test, made 

 as follows. Dilute the dioxide to be tested with nine parts distilled, 

 water. To 5 cc. of this solution (i-io) add 3 cc. of a 10 per cent 

 solution of potassium iodide and i cc. of 8 per cent, sulphuric acid, 

 in a standard test-tube. The color produced is matched against a 

 n/io iodine solution in a second standard test-tube. 1.8 cc. of 

 the standard solution is equivalent to i cc. of oxygen. 



Into graduated fermentation tubes with slender arms, having a 

 capacity of 25 cc, run 10 cc. of milk and 10 cc. of the standard 

 hydrogen dioxide, mix well in the bulb and at once run into the 

 arm, excluding all air from the upper end of tube. Set aside in the 

 incubator for i hr. at a temperature of 20° C. and record the 

 amount of gas formed at the end of this period. 



