EXAMINATION OF BILIARY CALCULI. 93 



a very similar chloroform sulphuric acid reaction, but whose 

 melting-point is 133-136). 



2. The residue B remaining on the filter is washed a few 

 times with ether, the upper part of the filter, which still con- 

 tains some cholesterin, is cut off, the filter filled with dilute 

 hydrochloric acid (1 : 3), and the filtrate poured repeatedly 

 upon the residue. 



3. The filtered solution C contains calcium salts, which 

 may be proved by making a portion of the solution alkaline 

 with ammonia, and adding acetic acid and ammonium ox- 

 alate; sometimes traces of copper are present, as may be 

 ; shown by the addition of a few drops of potassium ferro- 

 'Cyanide: brown color or precipitate of copper ferrocyanide. 



4. The residue D remaining on the filter is washed with 

 water till the wash-water is free from hydrochloric acid, the 

 filter is then dried in an air-bath, cut into pieces, and these 

 are heated in a dry flask with a little chloroform. The brown- 

 ish-yellow fluid resulting is then filtered through a dry filter. 



The solution contains bilirubin, C 32 H 36 N 4 6 . Let a por- 

 tion of this solution evaporate spontaneously on a watch- 

 glass and examine the residue under the microscope: small, 

 ill-defined, elongated rhombic plates or indistinct crystalline 

 grains of bilirubin (not to be confused with the cholesterin 

 crystals, which may still be present). Pour on the edge of 

 the watch-glass a drop of nitric acid which contains some 

 nitrous acid : play of colors of the Gmelin reaction (see chap- 

 ter on Urine, " Bile-pigments/' page 121). Bilirubin 1 is 

 isomeric with hsematoporphyrin (page 56), which gives 

 Gmelin's reaction indistinctly. 



Shake up the greater part of the solution with a weak 

 solution of sodium hydroxide: the pigment goes over into 

 the alkaline solution, while the chloroform is more or less 



1 According to Zaleski hsematoporphyrin has the formula 

 and is not isomeric with bilirubin, Zeit. physiol. Chem. 37,74 (1902). O. 



