ADULTERATIONS OF MILK 229 



acid to 50 c.c. of the milk in a flask and shake to curdle. Then 

 add 150 c.c. of ether, cork the flask, and shake well. Break up 

 the emulsion which forms by aid of a centrifuge, or if .the latter 

 is not available, extract the curdled milk by gently shaking with 

 successive portions of ether, avoiding the formation of an emul- 

 sion. Transfer the ether extract (evaporated to small volume if 

 large in bulk) to a separator funnel and separate the benzoic acid 

 from the fat by shaking out with dilute ammonium hydroxid, 

 which takes out the former as ammonium benzoate. Evaporate 

 the ammoniacal solution in a dish over the water-bath till all free 

 ammonia has disappeared, but before dry ness is reached add a 

 few drops of ferric chlorid reagent. The characteristic flesh- 

 colored precipitate indicates benzoic acid. Care should be taken 

 not to add the ferric chlorid until all the ammonia has been driven 

 off, otherwise a precipitate of ferric hydrate is formed." 



Detection of Salicylic Acid. Method of tfre Association of 

 Official Agricultural Chemists: " Proceed exactly as directed for 

 benzoic acid in the preceding section. On applying the ferric 

 chlorid to the solution after evaporation of the ammonia the well- 

 known violet color indicates salicylic acid. 



" Salicylic acid can also be detected by evaporating 10 c.c. of 

 the milk to dryness on a water-bath, pulverizing the residue, and 

 adding a few drops of ferric chlorid solution. The characteristic 

 purple color will appear if salicylic acid is present." 



Detection of Sodium Carbonate and Bicarbonate. Mix 10 c.c. 

 of the milk with 10 c.c. of alcohol and a few drops of a 1 per cent, 

 solution of rosolic acid. Carbonate present gives a rose red color, 

 while pure milk gives a brownish-yellow color. 



Roughly, the presence of sodium carbonate or bicarbonate can 

 be detected by evaporating about 10 c.c. of the milk to dryness on 

 a water-bath; a yellow color will appear if sodium carbonate was 

 present. Addition of an acid to the residue will cause effervescence. 



BIBLIOGRAPHY 



v. Behring: Hygienische Zeitschr., 1907, vol. 3, p. 632. 



Budde: Milchzeitung, 1903, vol. 44, p. 690. 



Chester and Brown: Delaware College Agri. Exper. Sta., Bull. 71, August, 1905. 



Heinemann: Jour. Amer. Med. Assoc., 1913, vol. 40, p. 1603. 



Herz : Quoted from Sommerfeld's Handbuch der Milchkunde. 



Leach: Food Inspection and Analysis. 



Official and Provisional Methods of Analysis: Association of Official Agricul- 

 tural Chemists. 



Reiss: Sommerfeld's Handbuch der Milchkunde. 



Reiss and Sommerfeld: Sommerfeld's Handbuch der Milchkunde. 



Richmond: Dairy Chemistry. 



Shaw: Chemical Testing of Milk and Cream, United States Dept. of Agri., 

 B. A. I., February 17, 1916. 



Tunnicliffe and Rosenheim: Jour, of Hygiene, 1901, vol. 1, p. 168. 



Van Slyke: Modern Methods of Testing Milk and Milk Products. 



