62 MILK 



water, the mixture is heated, precipitated with a 

 small amount of alcohol and a convenient 

 volume filtered. The filtrate is evaporated to 

 half its bulk. The presence of an alkali-carbon- 

 ate is easily ascertained by the usual tests. 



Borates. — Jenkins' method is convenient and 

 reasonably delicate. lo c.c. of milk are mixed 

 with 7 c.c. of hydrochloric acid, filtered, a strip 

 of turmeric paper dipped in the filtrate, and then 

 dried on a watch-glass on the water-bath. The 

 paper becomes red in the presence of borates. 



A simple test is to mix in a porcelain basin a 

 drop or two of the milk, a drop of hydrochloric 

 acid and a drop of alcoholic solution of turmeric 

 and evaporate to dryness on the water-bath. 

 The residue touched with ammonium hydroxid 

 will show a distinct greenish stain in the presence 

 of very small amounts of borates. 



It is obvious that the delicacy of both these 

 tests may be materially increased by concen- 

 trating the sample. As boric acid is volatile 

 with steam it is best to render the sample slightly 

 alkaline with sodium hydroxid before evaporating. 



Abrastol (Asaprol). — This is a calcium beta- 

 naphthol-sulphonate that has marked antiseptic 

 powers and has been used as a food preservative. 

 The following test suggested by Leffmann will 

 detect very small amounts. lo c.c. of the 

 sample are mixed with 0.5 c.c. of the solution of 



