174 THE DIGESTIVE FLUIDS. 



SPECTROSCOPIC TEST. If a dilute solution of sodium biliru- 

 binate in water is treated with an excess of ammonia and a small 

 amount of a solution of chloride of zinc, the liquid at first turns 

 a deep orange, but subsequently becomes olive brown, and finally 

 green. If this solution is examined spectroscopically, it will be 

 noted that the violet and blue portions of the spectrum are at first 

 quite dark, but subsequently the bands presented by an alkaline 

 solution of bilicyanin become apparent, and notably the one between 

 C and D, near C (see below). 



Isolation of Bilirubin. Bilirubin is most conveniently obtained 

 from the biliary concretions which are so often found in the gall- 

 bladder of cattle, and which consist almost entirely of the calcium 

 salt of the pigment. They are finely powdered and extracted with 

 ether and then with hot water, so as to remove the cholesterin and 

 the biliary acids which are present. The remaining material is 

 treated with hydrochloric acid, so as to liberate the pigment. It is 

 then washed free from acid with water, and subsequently with abso- 

 lute alcohol to remove the water and any biliverdin that may be 

 present. The pigment remains, and is now dissolved with boiling 

 chloroform. From this solution the chloroform is distilled off, the 

 residue extracted with absolute alcohol, so as to remove any bili- 

 fuscin, and the remaining bilirubin dissolved in a small amount of 

 chloroform and precipitated with alcohol. This procedure is 

 repeated until the substance has been obtained in pure form ; it 

 is then allowed to crystallize out from its chloroform solution on 

 cooling. 



Biliverdin. Biliverdin is found in the bladder-bile of many ani- 

 mals together with bilirubin, and is especially abundant in certain 

 herbivora, where the bile frequently presents a bright grass-green 

 color. It is said to occur also in the placenta of the bitch, in the 

 shells of certain mollusks, and in birds' eggs. Its relation to bili- 

 rubin has already been considered. In the bile it is present princi- 

 pally in the form of its sodium salt, and, like bilirubin, the free 

 pigment possesses acid properties ; this is termed biliverdinic acid, 

 but should not be confounded with the acid of the same name which 

 Kiister obtained from biliverdin on oxidation with sodium chromate 

 (see above). In acid bile biliverdin is found as such. Unlike 

 bilirubin, the free pigment is readily soluble in normal as well as in 

 neutral and acid bile. It is insoluble in water, ether, and chloro- 

 form, but dissolves in alcohol, glacial acetic acid, and solutions of 

 the alkalies. From the latter it is precipitated by the salts of the 

 alkaline earths and the heavy metals, as also by acids. On treating 

 an alcoholic solution of biliverdin with ammoniacal chloride of zinc 

 solution the fluid exhibits a green fluorescence. The green color of 

 the pigment is changed to yellow if its solution in acid alcohol is 

 treated with zinc. If chlorine-water is added instead, a blue color 

 develops at the bottom of the liquid, and above it layers present- 

 ing a violet, a red and a yellow color will be observed. On adding 

 an excess of chlorine-water the solution is decolorized. 



