EXAMINATION OF BILE. 87 



requires apparently more sulphuric acid, and is often not 

 equal in intensity to the original Pettenkofer's reaction. 



According to v. Udrdnszky * the best proportions for this 

 reaction are: 1 cc. of the alcoholic solution of the bile-acids, 

 one drop of the furfurol solution (0.1 per cent.), and 1 cc. of 

 concentrated sulphuric acid. 



Modification according to Neukomm. 



Use a 0.1 per cent, solution of the salts of the bile- 

 acids. Add to some drops of this solution a trace of sugar 

 solution, then one or more drops of dilute sulphuric acid, 

 and evaporate in a dish on the water-bath: a violet color 

 develops at the edge of the evaporating mixture. As soon 

 as this is distinctly perceptible stop the evaporation. 



Preparation of Glycocholic Acid. 



Dissolve the rest of the crystallized bile (with the excep- 

 tion of a small part to be kept) in a little water, pour some 

 ether on top of this solution, and then add dilute sulphuric 

 acid until a permanent and marked cloudiness appears. The 

 glycocholic acid separates gradually in fine silky needles. 

 Glycocholic acid is very difficultly soluble in cold water, 

 more readily in hot, and easily soluble in alcohol. The aque- 

 ous solution has a bitter-sweet taste, reacts acid, and decom- 

 poses the alkaline carbonates when heated with them. The 

 acid as well as the salts are dextrorotatory. 



Preparation of Taurocholic Acid. 



The preparation of this acid is best accomplished by 

 using dog's bile, in which it is the only acid present. To 

 show its presence m the crystallized bile, fuse 0.2 g. of this 



1 Zeit. fur physiol. Chemie, 12, 371. 



