i MILK 119 



Uaier and Neumann state, and this is corroborated by 

 Liihrig, that in normal milk the lime in the serum is from 

 13-18 mg. per 100 c.c., whilst in the case of milk or cream to 

 which saccharate of lime has been added the results are always 

 considerably higher. 



VII. THE ADDITION OF PRESERVATIVES. 



In most countries the addition of antiseptic or other foreign 

 materials to the milk is forbidden. This is a well-justified 

 course, for, apart from the fact that most preservatives cannot 

 be regarded as non-injurious from a hygienic standpoint, the 

 use of them must militate against the care and cleanliness 

 which ought to be exercised in dealing with milk. The sub- 

 stances which are usually added to rnilk to increase its keeping 

 properties are carbonate or bicarbonate of soda, boracic acid 

 and its salts, salicylic acid, benzoic acid, formaldehyde, and 

 hydrogen peroxide. 



1. Carbonate or Bicarbonate of Soda. 



Carbonate of soda is not used for its antiseptic properties, 

 for it possesses none, but because of its power of neutralising 

 the lactic acid which forms, and which would ultimately curdle 

 the milk. The development of the bacteria is in no way 

 hindered by the use of this "preservative," which must be 

 regarded as harmful, seeing that it permits of a milk being in 

 an advanced stage of decomposition without the appearance 

 indicating the fact. 



The use of carbonate or bicarbonate of soda was much 

 greater formerly, and is still common to a small extent in some 

 parts. Generally, about 1 g. of anhydrous soda is used to each 

 litre of milk. 



To prove the addition of carbonate or bicarbonate of soda to 

 a milk, Hilger's method can be used, which consists in diluting 

 50 c.c. of milk with 250 c.c. of water, heating it, and then 

 precipitating with a small quantity of alcohol. After the solid 

 matter has been filtered off, the filtrate is evaporated to half its 

 former volume and tested for an alkaline carbonate with litmus 

 paper, &c. 



