190 ADUI.TERATION OF MILK. 



In view of the contradictory mass of Evidence which is at 

 hand as shown by Kastle and Roberts (4), it would appear 

 that laws forbidding the use of preservatives in milk intended 

 for human consumption are certainly to be recommended as 

 safeguarding the public health. The strong, healthy stomach 

 may and can withstand strains to which the delicate digestive 

 organs of an infant or invalid would succumb. 



Tests for preservatives. A complete examination of a sample 

 of milk for preservatives would include tests for boracic acid 

 and its compounds, formaldehyde, fluorids, benzoic acid and 

 its compounds, salicylic acid and salicylates, peroxide of hydro- 

 gen, etc. Such thorough analytical work can be conducted 

 only in a well-equipped laboratory. It is assumed that the 

 man in charge of the work is an expert and has at his disposal 

 the necessary standard works describing the tests. For this 

 reason it is not considered necessary to reprint the methods for 

 making such determinations. The preservatives most com- 

 monly used are borax and formaldehyde. It is fortunate that 

 there are simple and reliable tests for these two. 



Borax. A preliminary test may be made for boric acid and 

 borates by immersing a strip of turmeric paper in about 100 cc. 

 of milk to which about 7 cc. of concentrated hydrochloric acid 

 has been added. If boric acid or borax is present, the paper 

 on drying will acquire a peculiar red color which is changed by 

 ammonium hydrate to a dark blue-green but is restored by acid. 

 The above mentioned reagents can easily be obtained at a drug 

 store. A positive reaction would indicate the presence of 

 borax but a negative reaction might not in all cases mean that 

 the material does not contain borax but would require further 

 examination where better laboratory facilities could be ob- 

 tained. 



Formaldehyde. This is without doubt the best preservative 

 of milk. So efScacious is this material that there are many 

 compounds to be found on the market under various names, 

 such as " callerine," " freezine," etc. These different prepar- 

 ations are weak solutions of formaldehyde, ranging from about 

 3% to 7% in strength. 



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