239 



ms.ms of a glass rod. A slaty color, changing to green, is 

 produced if borax is present."* 



" Salicylic Acid or Its Salts : The milk is coagulated by 

 means of a few drops of acetic acid and filtered, the filtrate is 

 shaken with ethyl ether in a separating funnel. The ether is 

 carefully drawn off and evaporated in a glass dish on the 

 water bath. The residue, if any, is treated with a very little 

 water, filtered, and a drop of neutral ferric chloride added. A 

 violet color indicates presence of salicylic acid or its salts."t 



" 20c.c. of milk are acidulated with sulphuric acid and shaken 

 with ether ; the ether solution is evaporated, and the residue 

 treated with alcohol and a little iron chloride solution ; a deep 

 violet color will be obtained'in the presence of salicylic acid."1: 



" Alkaline carbonates may be detected by the strong alka- 

 line character of the ash, and by its effervescing with dilute 

 acids. A quantitative determination may be made by titrating 

 the water solution of the ash with n/10 sulphuric acid, using 

 lakmoid as an indicator." 1[ 



"To lOc.c. of milk add lOc.c. of alcohol and a little of a one 

 per cent, rosolic acid solution. Pure milk will give a 

 brownish yellow color; milk to which soda has been added, a 

 rose red color. A control experiment with milk of known 

 purity should be made."§ 



'^ Formaldehyde or 'Formalin': A few drops of milk are 

 floated on a small amount of concentrated sulphuric acid, con- 

 taining a trace of ferric chloride. If formaldehyde is present, 

 a violet blue ring will appear at the line of demarkation."|| 



"A solution of diphenylamin is made with water and just 

 enough sulphuric acid to secure a proper solvent effect. The 

 milk to be tested, or better the distillate therefrom, is added 

 to this solution and boiled. If formalin is present, a white 



* Fariington and Woll's Testing Milk, p. 195. 

 t N. Y. City Board of Health Report, 1896, p. 169. 

 t Farrington and Woll's Testing Milk, p. 196. 

 t N. Y. City Board of Health Report, 1896, p. 169. 

 § Farrington and Woll's Testing Milk, p. 197. 

 II N. Y. City Board of Health Report, 1896, p. 169. 



