43 



one-eighth its volume. It is again filtered, and then shaken with 

 ether. Perchloride of iron added to the ether solution, will produce 

 a violet color if salycilic acid is present. Schulz states that a solu- 

 tion of salicylic acid in water, with some cupric sulphate solution, 

 becomes a beautiful emerald green. This reaction is even more 

 brilliant when the sodium salt is used, and can be easily recognized 

 when dissolved in the proportion of 1 : 2000 parts of water. Al- 

 cohol hastens the appearance of the color. Acids and ammonia 

 prevent the reaction. 



Boric acid and borax being more easily soluble, more active 

 and cheaper than salicylic acid, are used quite f reqiiently as preser- 

 vatives. To determine their presence, 60 c.c. of milk are coagulated 

 with some acetic acid, and the filtrate evaporated in a platinum 

 dish. The residue, after drying, is incinerated. The ashes are 

 then heated with some alcohol containing from 1 to 3 per cent, of 

 cone, sulphuric acid. When the alcohol is then lighted, it will 

 burn with a flame which appears green colored at the edges, if 

 boracic acid be present. H. Gilm proposes to use the following 

 method, which is said to have the advantage of not only pro- 

 ducing a greener flame, but one which appears uniformly colored. 

 The boric ether vapors produced by the boiling of boric acid, 

 concentrated sulphuric acid and alcohol, are passed through a 

 narrow tube into a wider tube standing in vertical position. The 

 mixture of air and vapors is then ignited at the upper end of the 

 wider tube. 



Quack preservatives, at very high prices, are also in use, and 

 widely advertised. The most widely known are : 



Aseptine, which is recommended for the preservation of milk and 

 cream, and which, according to Nettl and Fleck, consists merely of 

 finely pulverized boracic acid. 



Glacialine is a mixture said to contain mainly boracic acid 

 and borax. 



