On the Functions of the Bile as a Solvent. 



69 



k small volume of absolute alcohol, and once more cooling out of solu- 

 tion. The final product was dried in a desiccator over sulphuric acid 

 for some days. 



In the case of cholestearin the figures obtained for the solubility 

 were so low, that pure cholestearin preparations were made from 

 several sources in order to make certain of the result; but all the 

 specimens gave a like result. 



The cholestearin first used was prepared from a laboratory specimen 

 by repeatedly recrystallising from ether and from hot alcohol. The 

 second specimen was obtained by repeated recrystallisation from hot 

 alcohol and ether of the residue after taking out the lecithin from the 

 hot alcoholic extract of egg yolk by means of a small volume of 

 absolute alcohol as above described. Large characteristic cholestearin 

 crystals were easily obtained by this method in great abundance. A 

 third specimen was similarly prepared from ox brain, and a fourth from 

 human gallstones by the usual method of extraction. 



Comparative determinations were made of the solubilities in distilled 

 water, in 5 per cent, aqueous solution of bile salts, in 5 per cent, 

 aqueous solution of bile salts plus 1 per cent, of lecithin, and occa- 

 sionally in ox bile. Two methods were employed in carrying out 

 the determinations, which were all made at a temperature as close to 

 that of the human body as possible, viz., at 37° to 39° 0. 



In one method, an excess of the substance of which the solubility 

 was to be determined was heated to a temperature of 50° to 60° C. 

 with the solvent ; the mixture was allowed to cool to the required 

 temperature, and then filtered through paper in a funnel kept at body 

 temperature by a warm jacket. It was afterwards tested that the 

 filtrate became clear, when it was once more heated to body tem- 

 perature. 



The percentage dissolved is then estimated by determining the 

 amount of dissolved substance in a given volume, say 5 c.c, of the 

 filtered solution. This is done by evaporating to dryness, extracting 

 the fatty acids with ether (in the case of the soaps, after first convert- 

 ing into free fatty acids by the action of a mineral acid), and weighing- 

 after evaporating off the solvent. 



This method has some practical disadvantages which have precluded 

 its use except in the case of the determination of the solubility of the 

 sodium soaps in bile. In the first place, a considerable amount of 

 both solvent and solute must be used in order to obtain a workable 

 ■quantity of filtrate. It is also difficult to filter with some of the sub- 

 stances tested, and on extraction of the evaporated solution with ether 

 it is often impossible to obtain a clear ethereal solution. This method 

 has therefore only been carried out in the case of the sodium soaps and 

 bile. Here it has been used to determine the maximum amount which 

 -can be taken up by the bile from such a naturally-occurring mixture of 



