

EXAMINATION OF MILK. 



orange and the undissolved particles of albumin also take on 

 the same color. This reaction depends upon the conversion 

 of the aromatic group in the albumin molecule into nitro 

 derivatives. 



2. Millon's Reaction. Treat a small portion of the sub- 

 stance with a few cubic centimeters of water, add some 

 Millon's reagent, and heat to boiling. The albumin turns 

 brick-red. This reaction is due to the tyrosin group^ present 

 in the albumin molecule ; tyrosin gives the reaction in a strik- 

 ing manner, and the same is true of all derivatives of benzene 

 in which a benzene hydrogen atom is replaced by hydroxyl. 

 (0. Nasse.) 



3. Conduct towards an Alkaline Solution of Lead Hydroxide. 

 To some cubic centimeters of caustic soda solution add two 

 drops of a neutral lead acetate solution. The precipitate of 

 lead hydroxide first formed dissolves on shaking. Heat a 

 small portion of the albumin with this alkaline solution of 

 lead hydroxide; the mixture turns black in consequence of 

 the formation of lead sulphide. A part of the sulphur is 

 present in albumin in the unoxidized form and may be split 

 off by alkalies as potassium or sodium sulphides. 



4. Reaction of Adamkiewicz. Grind a part of the albumin 

 in a small mortar with some absolute alcohol, filter, squeeze 

 out the excess of alcohol, and grind with some cubic centi- 

 meters of ether, filter, and remove the excess of ether by pres- 

 sure. Use half of the albumin thus obtained for the reaction 

 of Adamkiewicz ; dissolve the albumin by warming with a 

 few cubic centimeters of glacial acetic acid, cool the solution, 

 (by dipping into water), and allow some concentrated sul- 

 phuric acid to flow slowly down the wall of the test-tube into 

 the acetic acid solution of the albumin: the fluids mix at the 

 surface of contact, giving a violet to purple color. 



According to Hopkins and Cole l this reaction is due to 



1 Proc. Roy. Soc., 68, 21 (1901). 



