BILE. 



white porcelain dish add a few drops of red nitric 

 acid. A precipitate will ensue around every drop, and 

 then a red, blue, green, and yellow coloration will pro- 

 ceed in rings from each drop as a centre, due to the 

 reaction of the colouring matters with nitrous and 

 nitric acid. 



16. To a few drops of bile placed in a porcelain dish 

 add a drop of a solution of cane-sugar, and then con- 

 centrated sulphuric acid drop by drop with agitation. 

 After a little time the mixture will assume a purple-red 

 colour, and show the following spectrum : 



A a BO 



Spectrum of Pettenkofer's test. 



The colour of the solution will be destroyed by 

 water and alcohol. 



17. In diseased conditions of the bile, in fatal cases 

 of cholera, the liquid contained in the gall-bladder 

 contains no bile-acids. 



Observe that in such cases the purple reaction just 

 described cannot be obtained even with the concen- 

 trated alcoholic extract. 



18. Boil purified bile dissolved in water with excess 

 of hydrochloric acid in a flask for several hours, until 

 a clear reddish fluid is obtained and a dark pitchy 

 resin is deposited. The resin is choloidic acid and 



