METHODS OF EXAMINING MILK 289 



amber colored bottle, well stoppered and in a cool place. 

 High temperatures break up the compound. The bottle 

 should be closed immediately after being opened to draw 

 off any of the solution. The solution must be tested by 

 titration from time to time in order to insure accurate re- 

 sults. 



To overcome the inconvenience of frequent tests of 

 the hydrogen peroxide solution, the N. Gerber Co., of 

 Leipsig, Germany, has prepared a tablet containing the 

 hydrogen peroxide in more stable form. One of these 

 tablets dissolved in 5 c.c. of water makes a 1 per cent, 

 solution of hydrogen peroxide. (It has also been estab- 

 lished by extensive experiments that one of these tablets 

 added to 10 c.c. of milk will give the same result as 3 c.c. 

 of a 1 per cent, hydrogen peroxide solution in 9 c.c. of 

 milk). 



The test is made as follows: 1. The bottles must 

 be well cleaned and sterilized by boiling for 15 minutes 

 before using. The use of water containing calcium must 

 be avoided. If not used at once the bottles are to be 

 tightly corked with rubber stoppers, which are also to 

 be sterilized by boiling. The bottles may be closed with 

 cotton plugs and sterilized in a hot-air sterilizer. Pipettes 

 should be sterilized before beginning a series of tests. 

 The pipette used for measuring the milk should be 

 washed out with cold water and then sterilized by filling 

 it with boiling water after each sample of milk is meas- 

 ured. 



2. Three c.c. of a 1 per cent, solution of hydrogen 

 peroxide is placed in the bottle ; then 9 c.c. of the milk to 

 be tested is added. The bottle is numbered to correspond 

 with the sample of milk. In testing individual milk, it 

 is recommended that the sample be taken from the entire 



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