CONTROL OF THE PUBLIC MILK SUPPLY 419 



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

 chloric acid has been added, and the solution filtered. A strip of turmeric paper mois- 

 tened 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 acid- 

 ulated 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 Prod- 

 ucts," Farrington and Woll, p. 248.) 



Test for Benzole 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, when 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 sul- 

 phuric 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 dis- 

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

 extractions, 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 sul- 

 phuric acid is again added, and the liquid shaken out with small quantities of ether. 

 On evaporation of the ether, the benzoic acid is left behind in almost pure state, the 

 only impurities being small quantities of fat or ash. 



The benzoic acid which is obtained is dissolved in a small quantity of warm water, 

 a drop of sodium acetate and neutral ferric chloride added, and the red precipitate of 

 benzoate of iron indicates the presence of the acid. ("Milk and Dairy Products," 

 Barthel, translated by Goodwin, p. 121.) 



85. Detection of Heated Milk. Certified milk or cream shall not be subjected 

 to heat unless specially directed by the commission to meet emergencies. 



86. Tests to determine whether such milks and creams have been subjected 

 to heat shall be applied at least once each month. 



Detection of Heated Milk Storch's Method. Five cubic centimeters of milk are 

 poured into a test tube; a drop of weak solution of hydrogen dioxide (about 0.2 per 

 cent.) which contains about 0.1 per cent, sulphuric acid, is added, and two drops of a 

 2 per cent, solution of paraphenylendiamin (solution should be renewed quite often), 

 then the fluid is shaken. If the milk or the cream becomes, at once, indigo blue, or the 

 whey violet or reddish brown, then this has not been heated or, at all events, it has not 

 been heated higher than 78C. (172.5F.); if the milk becomes a light bluish gray im- 

 mediately or in the course of half a minute, then it has been heated to 79 to 80C. 

 (174.2 to 176F.). If the color remains white, the milk has been heated at least to 

 80C. (176F.). In the examination of sour milk or sour buttermilk, lime water must 

 be added, as the color reaction is not shown in acid solution. 



Arnold's Guaiac Method. A little milk is poured into a test tube and a little tincture 

 of guaiac is added, drop by drop. If the milk has not been heated to 80C. (176F.) 

 a blue zone is formed between the two fluids: heated milk gives no reaction, but 

 remains white. The guaiac tincture should not be used perfectly fresh, but should 



