CHOLESTEROLS 321 



Tests. 



(1) Crystalline form of crystals separated from alcohol. 



(2) On running a drop of sulphuric acid (5 vols. of cone, acid to 



1 vol. of water) upon some crystals on a glass slide, covered with a 

 cover slip, the crystals become red. A drop of iodine solution placed 

 against the cover slip and brought into contact with the crystals 

 by drawing it through with filter paper, changes the colour of the 

 crystals at the points of contact to violet, blue and black. 



(3) Salkowskfs Reaction. A small quantity of dry cholesterol 

 is dissolved in a little chloroform in a dry test tube. An equal 

 volume of concentrated sulphuric acid is added and the liquids mixed. 

 The chloroform rises to the surface coloured at first red, then purple, 

 and the sulphuric acid is yellow and shows a green fluorescence. If 

 the chloroform be poured into a basin it becomes blue, green and yellow. 

 It is decolorised if water be added, but the colour returns on adding 

 strong sulphuric acid. The colour is only stable in the presence of 

 acid. If the sulphuric acid be diluted with glacial acetic acid it be- 

 comes red, but still shows a green fluorescence. 



(4) Liebermanris Reaction. A little cholesterol is dissolved in about 



2 c.c. of chloroform in a dry test tube, 2 or 3 drops of acetic anhydride 

 are added and drop by drop concentrated sulphuric acid. A red colour, 

 which becomes blue and finally bluish-green, is formed. 



(5) Tschugaiejfs. Reaction. A little cholesterol is dissolved in glacial 

 acetic acid, excess of acetyl chloride and a piece of fused zinc chloride are 

 added and the mixture warmed for 5 minutes. The solution becomes red 

 with a green fluorescence. 



(6) Neubergs Reaction. If to some cholesterol dissolved in 2 or 3 c.c. 

 of absolute alcohol a trace of rhamnose (or a solution of methyl furfural) be 

 added and sulphuric acid be run under the solution, a red ring is formed at 

 the junction ; on mixing and keeping the mixture cold, the red colour diffuses 

 throughout the fluid. 



Isocholesterol. C 27 H 4( ,O. 



Isocholesterol has been found together with cholesterol in lanolin. 

 Coprosterol. C 27 H 48 O. 



Coprosterol has been found in human faeces ; it is probably formed by 

 the reduction of cholesterol in the large intestine. 



Hippocoprosterol. 



Two compounds, C 27 H 54 O and C 27 H 52 O, have been isolated from horses' 

 manure and are probably reduction products of phytosterol. 



Spongosterol. C 19 H 32 O ? 



This compound has been isolated from sponges and is very like cholesterol 

 in appearance but melts at 119-120. 



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