COLOR REACTIONS AND SPLIT PRODUCTS 109 



drate groups are cleaved off into the residues. 

 Casein gives a very weak Molisch reaction, and 

 casein residue a strong reaction; this may be 

 due to tryptophane, but we think not, as the 

 casein residue gives only a weak tryptophane 

 reaction. Casein residue does not reduce Fehl- 

 ing's solution even after boiling with dilute hy- 

 drochloric acid. Part of the residue is insolu- 

 ble in 10 per cent alkali and this insoluble part 

 gives the Molisch reaction and also tests for 

 nitrogen. 



7. The proteins and their split products all 

 give the Adamkiewicz reaction indicating that 

 they all contain the tryptophane group. Solu- 

 tions of tyro sine give pinkish violet colors which 

 are similar to the tryptophane reactions in di- 

 lute solutions. 



8. The protein poisons do not give good Hop- 

 kins-Cole reactions when performed in the reg- 

 ular way. The proteins and residues do. They 

 all give good positive reactions when furfural 

 is added. The protein poisons probably give 

 negative reactions because they contain no car- 

 bohydrate. 



9. Benedict's modification of Hopkins-Cole 

 reagent gives similar results both with and 

 without furfural. 



10. The Acree Rosenheim formaldehyde test 



