298 FILTRATION AND HEATING OF MILK 



indirectly tends to foster negligence and uncleanliness 

 in the production and distribution of milk, and prevents 

 the spread of efforts to improve the conditions which 

 prevail at the farms and dairymen's premises. 



Although boric acid is, perhaps, not so injurious in 

 small doses as formalin or salicylic acid, its addition to 

 milk should be prohibited, and the law strictly enforced. 

 These compounds do not preserve by eliminating or 

 destroying the bacteria, and they are only used to make 

 a dirty milk appear or behave as a clean sample. 



For improving the keeping qualities of milk, it is best 

 to depend upon cleanliness of the farm and dairy, and 

 the maintenance of the product at a low temperature up 

 to the time that it is needed for consumption. 



During the last few years many investigations have 

 been made upon the bactericidal power of hydrogen 

 peroxide, a compound with somewhat poisonous pro- 

 perties, but which under certain conditions is readily 

 decomposed into the two harmless substances, water and 

 oxygen, thus : 



H 2 O 2 - H 2 O + O. 



The free oxygen is given off in an active " nascent " 

 state, in which condition it is able to destroy the vitality 

 of bacteria and their spores. 



The addition of small quantities to milk has been 

 found to kill off the bacteria in it and render it sterile. 



Its action is materially decreased by minute amounts 

 of acids, and at low temperatures the quantity it is 

 necessary to add to milk to destroy all bacteria present 

 in it, is too great to allow of the milk being used for 

 human consumption afterwards. However, at higher 

 temperatures, very small quantities suffice for sterilizing 



