Standards for Certified Milk. 267 



sulphate is connected, after adding 50 c. c. of a concentrated soda solution (1 pound 

 "pure potash" dissolved in 500 c. c. of distilled water and allowed to settle); the 

 contents of the Jena flask are now heated to boiling, and the distillation is continued for 

 40 minutes to an hour, until all ammonia has been distilled over. 



The excess of acid in the Erlenmeyer receiving flask is then accurately titrated 

 back by means of a tenth-normal standard ammonia solution, using a cochineal solution 

 as an indicator. From the amount of acid used the per cent of nitrogen is obtained ; 

 and from it the per cent of casein and albumen in the milk by multiplying by 6.25. 

 The amount of nitrogen contained in the chemicals used is determined by blank ex- 

 periments and deducted from the nitrogen obtained as described. (Farrington and Woll, 

 Testing Milk and Its Products, p. 221.) 



82. Coloring matter and preservatives. All certified milks 

 and creams shall be free from adulteration, and coloring matter 

 shall not be added thereto. 



83. Tests for the detection of added coloring matter shall 

 be applied whenever the color of the milk or cream is such as to 

 arouse suspicion. 



Test for coloring matter. The presence of foreign coloring matter in milk is 

 easily shown by shaking 10 c. c. of the milk with an equal quantity of ether; on 

 standing, a clear ether solution will rise to the surface; if artificial coloring matter 

 has been added to the milk, the solution will be yellow colored, the intensity of the 

 color indicating the quantity added ; natural fresh milk will give a colorless ether 

 solution. (Testing Milk and Its Products, Farrington and Woll, p. 244.) 



84. Tests for the detection of formaldehyde, borax, and bo- 

 racic acid shall be applied at least once each month. Occasionally 

 application of tests for the detection of salicylic acid, benzoic acid, 

 and the benzoates is also recommended. 



Test for the detection of formaldehyde. Five cubic centimeters of milk is 

 measured into a white porcelain dish, and a similar quantity of water added ; 10 c. c. 

 of HC1, containing a trace of Fe2 Clo, is added, and the mixture is heated very 

 slowly. If formaldehyde is present, a violet color will be formed. (Testing Milk 

 and Its Products, Farrington and Woll, p. 249.) 



Test for ~boracic acid (borax, borates, preservaline, etc.}. One hundred cubic 

 centimeters of milk are made alkaline with a soda or potash solution, and then evaporated 

 to dryness and incinerated. The ash is dissolved in water, to which a little hydrochloric 

 acid has been added, and the solution filtered. A strip of turmeric paper moistened 

 with the filtrate will be colored reddish brown when dried at 100C. on a watch glass, if 

 boracic acid is present. 



If a little alcohol is poured over the ash to which concentrated sulphuric acid 

 has been added, and fire is set to the alcohol, after a little while this will burn with 

 a yellowish-green tint, especially noticeable if the ash is stirred with a glass rod 

 and when the flame is about to go out. (Testing Milk and Its Products, Farrington 

 and Woll, p. 247.) 



Test for salicylic acid (salicylates, etc.}. Twenty cubic centimeters 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-chlorid solution ; a deep violet 

 color will be obtained in the presence of salicylic acid. (Testing Milk and Its Products, 

 Farrington and Woll, p. 248.) 



Test for benzoic acid. Two hundred and fifty to five hundred cubic centimeters 

 of milk are made alkaline with a few drops of lime or baryta water, and then evaporated 

 to about a quarter of the bulk. Powdered gypsum is stirred into the remaining liquid 

 until a paste is formed, which is then dried on the water bath. The gypsum only 

 serves to hasten the drying, and powdered pumice stone or sand can be used equally 

 well. When the mass is dry, it is finely powdered and moistened with dilute sulphuric 

 acid and shaken out three or four times with about twice the volume of 50 per cent 

 alcohol, in which benzoic acid is easily soluble in the cold, the fat only being dissolved to 

 a very slight extent or not at all. The acid alcoholic liquid from the various extrac- 

 tions, which contains milk sugar and inorganic salts in addition to the benzoic acid, 

 is neutralized with baryta water and evaporated to a small bulk. Dilute sulphuric acid 



