CHOLESTERIN. 
23 
alcoholic extract of the brain or spinal cord; on cooling, the cholesterinj to- 
gether with protagon ami cerebrin, separates out. From this mixture the 
cholesterin is dissolved out with ether, and the ether distilled off. To 
get rid of traces of lecithin it is heated for an hour with alcoholic potash ; 
this decomposes the lecithin, and the residue obtained by evaporating to 
dryness is dissolved in a mixture of alcohol and ether: from this solution, 
cholesterin crystallises out as its solvents evaporate off. 
Cholesterin is readily obtained from gall stones by simply extracting 
them with boiling alcohol, and treating with alcoholic potash to free it 
from extraneous matter. 
Like the fats, cholesterin is insoluble in water, hut freely soluble 
in hot or cold ether, glycerine, benzol, hot alcohol, and chloro- 
form. From anhydrous ether or chloro- 
form it separates in the form of needles, 
containing no water of crystallisation : 
from alcohol, or ether containing water, 
it separates in the form of rhombic, 
bright taldes, which contain a mole- 
cule of water of crystallisation, and 
are easily identified by the microscope 
(Fig. 6). * 
Dry cholesterin melts at 145°, distils in 
nir no at 360° 0. ; its specific rotatory power 
is (a) D = - 31° - 6. It may he recognised by 
the following colour tests : — 
1. With iodine and concentrated sulphuric acid the crystals give a 
play of red, green, and blue. 
2. Salhowski's reaction} — The cholesterin is dissolved in chloroform 
and an equal volume of concentrated sulphuric acid added ; the solution 
becomes first red and then purplish, while the sulphuric acid is dark red 
with a green fluorescence. On pouring off the chloroformic solution, it 
becomes green and finally yellow. 
3. Liebermann-Burchard's reaction. 2 — This is a very delicate test, and 
is stated to be capable of detecting one part of cholesterin in 20,000 of 
solvent. The cholesterin is dissolved in 2 c.c. of chloroform, and ten 
drops of acetic anhydride are added, and then concentrated sulphuric 
acid drop by drop. The mixture becomes first red, then blue, and 
finally green. 
Cholesterin is a monatomic alcohol, the formula of which has been 
given as C 20 H 43 OH and <', 7 H 4 -<)H. The second formula was first 
ascribed to the substance by Reinitzer, 3 and it is probably the correct 
one, as it has been confirmed by the careful work of Obermiiller. 4 These 
observers have prepared a large number of compounds and derivatives 
of cholesterin, but its constitution still remains unknown. 
Fig. 6.- Cholesterin crystals. 
After Frey. 
The subject is complicated by the circumstance that there are several 
isomeric cholesterins. 
1 Arch. f. d. ges. Physiol., Bonn. BJ. vi. 
2 Liebermann, B< r. d. deidsch. chem. Gesellsch., Berlin, Bd. xviii. S. 1S04 ; Burchard, 
" Beitriige zur Kenntniss der Cholesterine," Rostock, 1889. 
3 Reinitzer, Monatsh. f. Chem., Wien, 1888, Bd. ix. s. 421. 
4 Arch. f. Physiol., Leipzig, 1889; Ztschr. f. physiol. Chen., Strassburg, 18S9, Bde. 
xv. S. 37; xvi. S. 143, 152. 
