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 dryness 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 the 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 Zeitsohr., 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: Pood 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. 



