422 THE LIVER. 



Cholesterin is insoluble in water, dilute acids, and alkalies. It is 

 neither dissolved nor changed by boiling caustic alkali. It is easily 

 soluble in boiling alcohol, and crystallizes on cooling. It dissolves readily 

 in ether, chloroform, and benzene, and also in the volatile or fatty oils. 

 It is dissolved to a slight extent by alkali salts of the bile-acids, better 

 in the presence of oleic soap (GERARD 1 ). The solutions in ether and 

 chloroform are levorotatory, (a) D = 31.12 (2 -per cent ethereal solu- 

 tion) . 



Among the many compounds of cholesterin the propionic ester 

 C 2 H 5 .CO.O.C27H4 5 is of special interest because of the behavior of the 

 fused compound on cooling, and it is used in the detection of choles- 

 terin. For the detection of cholesterin use is made of its reaction with 

 concentrated sulphuric acid, which gives colored products. 



If a mixture of five parts sulphuric acid and one part water acts on 

 cholesterin crystals, they show colored rings, first a bright carmine-red 

 and then violet. This fact is employed in the microscopic detection 

 of cholesterin. Another test, and one very good for the microscopical 

 detection of cholesterin, consists in treating the crystals first with the 

 above dilute acid and then with some iodine solution. The crystals 

 will be gradually colored violet, bluish green, and a beautiful blue. 



SALKOWSKi's 2 Reaction. The cholesterin is dissolved in chloroform 

 and then treated with an equal volume of concentrated sulphuric acid. 

 The cholesterin solution becomes first bluish red, then gradually more 

 violet-red, while the sulphuric acid appears dark red with a greenish 

 fluorescence. If the chloroform solution is poured into a porcelain dish 

 it becomes violet, then green, and finally yellow. 



LIEBERMANN-BURCHARD'S 3 Reaction. Dissolve the cholesterin in about 

 2 cc. chloroform and add first 10 drops of acetic anhydride and then 

 concentrated sulphuric acid drop by drop. The color of the mixture 

 will first be a beautiful red, then blue, and finally, if not too much 

 cholesterin or sulphuric acid is present, a permanent green. In the pres- 

 ence of very little cholesterin the green color may appear immediately. 



NEUBERG-RAUCHWERGER'S 4 Reaction. With rhamnose, or better 

 still with d-methylfurfurol and concentrated sulphuric acid, an alcoholic 

 solution of cholesterin gives a pink ring, or after mixing the liquids and 

 cooling, a pink solution. On proper dilution an absorption-band can 

 be seen just beginning before E and whose other side coincides with 6. 

 This reaction is of interest because it is also given by bile-acids, somo 



1 Compt. rend. soc. biol., 58. 



2 Pfluger's Arch., 6. 



3 C. Liebermann, Ber. d. deutsch. chem. Gesellsch., 18; 1804, H. Burchard, Bei- 

 trage zur Kenntnis der Cholesterine, Rostock, 1899. 



4 Salkowski's Festschrift, 1904. 



