APPENDIX 471 



2. Apply Millon's and the Xantho-proteic tests. 



(a) A well-marked reaction indicates proteins of Kossel's 3rd 

 and 4th groups, (b) A faint reaction (combined with a 

 distinct Biuret, and the absence of coagulation on boiling) 

 points to gelatine ('2nd group). (Confirm by seeing if 

 the solution gelatinises on cooling). 

 If the Biuret Test gives a Violet Colouration, 



A. Add a drop or so of dilute acetic acid and boil. A 



coagulum points to native proteins To ascertain which 

 of these is present (i.e. albumin or globulin), half saturate 

 some of the solution with (NH 4 ) 2 S0 4 . A precipitate 

 indicates globulin ; filter ; if the nitrate still gives a 

 coagulum on boiling, albumin is present. 



B. Carefully neutralise some of the solution. A precipitate 



may be : 



1. Alkali Meta-protein original^ the precipitate re- 



fluid alkaline ! dissolves on adding 



2. Acid Meta-protein original f excess of acid or 



fluid acid J alkali. 



3. Nucleo-protein original fluids precipitate does not 



alkaline I disappear on adding 



4. Mucin original fluid alka- 1 a moderate excess 



line J of acid. 



To distinguish between Nucleo-protein and Mucin. This is 

 possible only when a large amount of these bodies is present. 

 The acetic acid precipitate is collected on a filter paper, washed 

 with acidulated water, and divided into two portions a and b. 



(a) Boil with 20 per cent. HC1 for 10 minutes; cool; 



neutralise ; apply Trommer's test. A positive reaction 

 points to mucin. 



(b) Melt in a crucible with fusion mixture; after the ash 



cools, dissolve it in nitric acid and add molybdate of 

 ammonia solution. A yellow precipitate on warming 

 indicates Nuclein. 



If the Biuret Test gives a Rose Pink Colouration, add a few 

 drops of concentrated pure nitric acid. 



A. A white precipitate, which clears up on warming and 

 returns on cooling, points to Proteose. Confirm by the 

 salicyl sulphonic acid test. 



If proteose be present, saturate some of the original 

 fluid, from which native proteins have been separated 

 by boiling, with sodium chloride. A precipitate indicates 



