90 Transactions Tennessee Academy of Science. 



Another example that might be mentioned is the use of sodium 

 carbonate in milk, although this is probably not as common now as 

 formerly. A little carbonate added to milk does not preserve it, 

 but does neutralize the acid as rapidly as it is formed and thus 

 keeps the milk tasting sweet. In the meantime decomposition 

 has been going on right along, probably even more rapidly, be- 

 cause of the alkaline reaction favoring bacterial growth, until 

 finally, after a few days, the milk may contain an enormous num- 

 ber of bacteria. 



Many preservatives are on the market under fanciful names 

 and bearing labels describing wonderful properties. They are 

 quite analogous to some of the numerous "beauty preparations" 

 sold, in that a small quantity of a cheap article is given a fancy 

 name and wonderful properties are claimed for it, and it is sold 

 for a high price. They usually bear statements that they are 

 absolutely harmless and can not be detected by any chemical 

 analysis. These statements are as false as the other claims made. 



The number of preservatives in common use is limited to only 

 a few. Some are better for one class of foods and others for other 

 classes. When a sample is received for analysis the chemist usu- 

 ally knows that his search will be limited to probably not more 

 than two or three substances as being the most likely to be found. 

 In the case of milk, for instance, formaldehyde or borax would 

 be expected ; with sausage, sulphites or borax. It might be men- 

 tioned that a mixture of borax and boric acid is more efficient 

 than either alone ; they are frequently used together, and ordina- 

 rily are tested for in the same manner. Before the use of formal- 

 dehyde, which is comparatively recent, borax or boric acid was 

 the most common preservative for milk. 



In testing for preservatives the procedure depends upon cir- 

 cumstances. In some cases it is ])ossible to apply the test directly 

 to a portion of tbc sample; in others the preservative must be 

 first separated from the other substances and isolated in more 

 or less pure condition ; while in still others a test ma\- he made 

 incidental to some other dcterminalion. 



The testing of some foods for preservatives is often ])racticable 

 in the home ; however, too much reliance should not be placed 

 ujjon the results unless the one making the tests has had some 

 ex])eriencc. It is usually not (hliicnlt to examine one of the ordi- 



