152 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



possible by heating in an evaporating-d^ ^ nd also in part 

 by pouring off the water), then, when it is perfectly cold, it is 

 broken up as finely as possible, placed in a flask, treated sev- 

 eral times with ether until it is almost entirely decolorized, 

 and then filtered. 



The ether extract C is distilled; on standing the residue 

 yields cholesterin, which is pressed between filter-paper and 

 identified by the chloroform sulphuric acid reaction (see 

 chapter on Biliary Calculi, page 91). The paper, which 

 was used to free the cholesterin from its mother -liquor, is 

 extracted with ether, and this is examined with the spectro- 

 scope (lute in). When the treatment with baryta-water is 

 long continued, however, the lutein is frequently so changed 

 that it cannot be detected in this way with certainty. It is 

 therefore advisable to use the reserved part of the original 

 ether solution for its detection. When this is examined 

 spectroscopically the blue of the spectrum appears com- 

 pletely absorbed; on diluting with ether to the proper point 

 an absorption-band between the green and the blue appears, 

 and also a suggestion of a second band in the blue. A por- 

 tion of the ether extract quickly becomes colorless when nitric 

 acid is added, after giving a transient green color. Evapo- 

 rate the remainder of the reserved part of the ether solution 

 on the water-bath and dissolve the residue in a little chloro- 

 form. 



Shake a part of the chloroform solution with a dilute solu- 

 tion of sodium hydroxide: the coloring matter is not with- 

 drawn from the chloroform by the alkali (distinction from 

 bilirubin or hsematoidin). 



To another part of the chloroform solution add some 

 strong nitric acid and shake: at first a blue color and then 

 decolorization. 



The residue D is ground in a mortar with an excess of 

 hydrochloric acid, the pasty mass placed in a separating- 



