ELEMENTARY CHEMICAL PHYSIOLOGY 



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called isocholesterol, is found in sebum and lanolin (purified wool 

 fat), and another coprosterol is found in the faeces. 



Preparation of Cholesterol from Gall-Stones. The gall-stones are finely ground 

 and boiled with 95 per cent, alcohol. The alcoholic extract is filtered hot and 

 allowed to cool, when crystals of cholesterol separate out and can be filtered 

 off, preferably with suction, using a perforated porcelain plate fitted in a 

 glass funnel and covered with a disc of filter paper. The crystals are washed 

 with a little cold alcohol, and may be re-crystallised from hot alcohol. 



Cholesterol is recognised by a number of colour reactions, of 

 which the most important are the following : 



FIG. 176. Crystals of cholesterol magnified 300 diameters. 



EXPERIMENT IX. Place some cholesterol crystals on a micro- 

 scopic slide and distribute them with a glass rod, and examine 

 under the microscope ; or better, dissolve some in absolute alcohol, 

 place a drop of the solution on a slide, and allow it to evaporate. 

 The crystals are colourless, glancing rhombic plates having usually 

 a square piece removed from one corner (Fig. 176). The crystals 

 give distinctive colour reactions. 



Cover the cholesterol crystals with a cover slip and allow a 



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