CH. II.] EGG-WHITE. 49 



40. The action of mineral acids on albumins and globulins. 

 (Heller's test.) Place a few cc. of strong nitric acid in a narrow 

 test-tube. By means of a pipette add an equal volume of dilute 

 serum or egg-white, inclining the tube during the addition so that 

 the protein solution is "layered" on the surface of the acid. A 

 white ring appears at or immediately above the junction of the 

 two fluids. 



NOTE. This is one of the most important tests for albumins in urine. 

 The reaction is also given by HC1 and H 2 SO 4 , but not so readily as by HNO 3 . 

 The primary proteoses also give a precipitate but this is soluble on warming. 



G. The chemistry of egg-white. 



41. In egg-white which has been well beaten with a whisk 

 (to break up the containing membranes), and diluted with four times 

 its volume of distilled water, note a precipitate of ovo-mucin and 

 globulin. Perform the following tests : 



(a) Take the reaction to litmus. It is alkaline. 



(b) Cautiously neutralise with dilute acetic acid. A slight 



increase in the precipitate of ovo-mucin and globulin is 

 noticed. Remove this by nitration if necessary, and 

 with the nitrate perform the following reactions : 



(c) Boil a portion. A coagulum is formed, indicating the. 



presence of either a globulin or an albumin. 



(d) Make another portion very faintly alkaline by the addition 



of a drop or two of 2 per cent. Na 2 CO 3 . Now add an 

 equal bulk of saturated (NH 4 ) 2 SO 4 . A slight precipitate 

 of globulin or albumin is formed. Filter this off, and 

 boil a portion of the nitrate with a drop of I per cent, 

 acetic acid. A coagulum of albumin is formed. Saturate 

 the remainder of this nitrate with ammonium sulphate 

 by grinding with the solid in a mortar. A precipitate 

 of albumin is formed. 



(e) Completely remove the globulin and albumin by boiling. 



Filter and apply Millon's or the xanthoproteic protein 

 test to the filtrate. Protein is found in small quantities. 



