64 MILK 



vestigations of Rentschler to kill quickly many 

 forms of microbes, and may be applicable to the 

 purification of milk, when, as in war, systematic 

 protection and inspection are not possible. 



Preservation of Samples. — For the preservation 

 of milk samples for a day or two, refrigeration 

 is the best method. Sterilization in the ordinary 

 steam sterilizer used in preparing culture-media, 

 wiU enable milk to be kept for a considerable 

 time if in a flask closed with a cotton plug. 

 Several preservatives have been proposed for 

 keeping samples. Richmond found small amounts 

 of hydrofluoric acid effective, but it has been but 

 little used. Formaldehyde is very eflBcient; in 

 large amount it increases the total solids, inter- 

 feres with the reactions of the proteins and simu- 

 lates some of the reactions of the carbohydrates. 

 A couple of drops of commercial formalin to 25 

 c.c. win preserve a sample for several days. 



