68 



Messrs. B. Moore and W. H. Parker. 



which dissolves out the surplus of alkali and inorganic salts. The 

 soaps were next converted into free fatty acids by treatment with 

 dilute hydrochloric acid, and the mixture of fatty acids was thoroughly 

 washed by warming with water. The free acids were again con- 

 verted into soaps by very slight excess of caustic soda, dissolved in 

 boiling water, precipitated by cooling, washed with cold water, dried 

 in a water bath, powdered, and kept in a glass-stoppered bottle. 



The mixed calcium and magnesium soaps were prepared from these 

 by precipitation from solution in hot water with calcium chloride and 

 magnesium sulphate respectively, washing thoroughly with water, and 

 drying on a water bath. 



The pure oleic acid and oleates used were prepared from a sample 

 of pure oleic acid by Merck. 



The pure palmitic acid was obtained from bereberry tallow by 

 repeated partial recrystallisation from alcohol until a constant and 

 .accurate melting point was obtained. The sodium soap was obtained 

 by neutralising with caustic soda and recrystallising from hot alcohol ; 

 i:he magnesium and calcium soaps by precipitation of the sodium salt 

 in hot aqueous solution by the appropriate salts, washing by decanta- 

 ,tion with cold water, and drying. 



The pure stearic acid and stearates were similarly prepared from 

 .commercial stearin, and their purity tested by melting-point deter- 

 minations for the free acid. 



The lecithin used was prepared from yolk of egg by the follow- 

 ing modification of the method of Hoppe-Seyler : The yolks were 

 separated, beaten up into a common mass and extracted with five times 

 their volume of 95 per cent, alcohol at a temperature of 50° to 60° C. 

 for about two hours. The precipitated proteid and membrane was 

 separated off by pressing through cheese cloth, the filtrate was allowed 

 to cool to about 30° C. and separated from a certain amount of fatty 

 •oils which became pressed through along with the alcoholic extract. 

 The alcoholic extract was evaporated down to a syrup at a temperature 

 of about 60° C. on the water-bath, and then taken up in a small 

 volume of absolute alcohol at a temperature of 40° to 50° C. This 

 extract was next surrounded by a freezing mixture and kept at a 

 temperature of - 5° to - 10° C. for some hours, which precipitates 

 the greater part of the lecithin. This was removed by decantation 

 and filtering through a chilled funnel, purified by again dissolving in 



precipitant is required. !N~ot even any sodium oleate is dissolved by the cold 

 water, as can be shown by first throwing into cold water, then removing the soap 

 and saturating the water with sodium chloride, when scarcely a trace of a preci- 

 pitate is obtained. JNor are acid soaps formed by this method of preparation, on 

 account of dissociation of the alkali, for on incineration of the soaps and titration 

 of the residue as sodium carbonate, we have obtained almost the theoretical yields 

 required for neutral soaps. 



