DETECTION OF PRESERVATIVES. 



In order to prevent milk from souring and to deceive 

 the customer as to the freshness of it, a number of dififer,- 

 ent preparations are made use of as preservatives. In 

 some cases these preservatives are used for the purpose of 

 preventing the curdling of the milk samples which are to 

 be subjected to analysis, and which for example have to 

 be sent a long distance during hot summer months. To 

 such a procedure no objection could be raised. If, how- 

 ever, milk thus treated be ofifered for sale as food, vigor- 

 ous protestations should be made against it from a hy- 

 gienic standpoint. Such milk should be rejected as food 

 and by all means as food for infants. All assertions and 

 opinions to the contrary are prejudicial and unreliable. 



The objection to the use of preservatives is based on 

 the fact that they hinder or prevent coagulation. On this 

 account it is impossible to judge of the age of the milk or 

 to decide whether it is fit for use. Concerning the value 

 of various preparations commonly used as preservatives, 

 it may be said that sodium carbonate and sodium bicar- 

 bonate are not especially active as germicides. In fact, 

 many of the pathogenic micro-organisms such as cholera 

 bacilli, develop only in alkaline culture-media. Borax 

 and boric acid act slightly as bacteriacides, while forma- 

 lin and salicylic acid act strongly. The latter, however, 

 is entirely ineffective against typhus bacilli. Benzoic 

 acid and hydrogen peroxide are effective only when used 

 in large quantities. 



In practice the following are quite extensively used : 

 borax and boric acid, sodium carbonate, salicylic acid, 

 benzoic acid, formalin, chromium — , mercury — , and am- 

 monium salts, and sodium fluoride. The last four are 

 used only for analytical work. The first are found most 

 frequently in milk as sold by the unscrupulous purveyor. 



