BILE-PIGMENT. 315 



composed with hydrochloric acid, which extracts the baryta ; the 

 fat is removed by ether from the residue, which is then dissolved 

 in alcohol. 



Platner precipitates the bile- pigment by digesting the bile with 

 hyclrated protoxide of tin ; the light green deposit which is 

 formed, after being well washed with water, is shaken with spirit 

 containing sulphuric acid, and filtered; the pigment is thrown 

 down in the form of a green flocculent precipitate on the addition 

 of water to the filtered green solution. 



Scherer separated the bile-pigment from urine containing large 

 quantities of it by means of chloride of barium, in the two following 

 ways : he either decomposed the baryta-compound with carbonate 

 of soda, threw down the pigment with hydrochloric acid from the 

 soda-solution, and purified it by solution in alcohol containing 

 ether, by washing with water, &c. ; or the baryta-compound was 

 extracted with alcohol containing hydrochloric acid, the solution 

 evaporated, extracted with water, and then treated in the manner 

 above described. 



Tests. Unless the amount of bile-pigment in a fluid be not too 

 minute, nitric acid, especially if it contain a little nitrous acid, 

 gives the very characteristic play of colours which we have already 

 described. When, however, the colouring matter is present in 

 small quantity, or when it has already undergone a partial modi- 

 fication, nitric acid often fails to give any appreciable reaction. 

 Schwertfeger's* method in such cases is to precipitate the fluid 

 with basic acetate of lead, and to extract the precipitate with 

 alcohol containing sulphuric acid : if any of the pigment be 

 present, the alcohol assumes a green tint. Heller^ recommends 

 that a little soluble albumen should be added to the fluid to be 

 examined (unless, indeed, it be already albuminous), which must 

 be precipitated by an excess of nitric acid; if any pigment be 

 contained in the fluid, it will communicate a bluish or greenish 

 blue tint to the coagulated albumen. Heller observes that if am- 

 monia be carefully poured upon urine which contains unchanged 

 bile-pigment, the surface of the fluid assumes a red colour. 



Physiological Relations. 



Occurrence. Bile-pigment usually occurs in fresh bile in a 

 state of solution ; often, however, it is in a state of suspension. 

 It almost always constitutes the nuclei of gall-stones ; and we some- 



* Jahrb. f. prakt. Pharm. Bd. 9, S. 375. 

 t Arch. f. Chem. u. Mikrosk. Bd. 2, S. 95. 



