112 FIXED OIL, ETC. 



Of lauric acid, Oudemans observes that it is easily volatile with 

 the vapour of water, which is not the case with myristic and 

 oleic acid ( 15). (Myristic and other fat-acids may however be 

 distilled in vacuo.) 



Oleic and stearic acids may be separated, according to David, 1 by 

 precipitation from alcoholic solution with glacial acetic acid (1 

 volume to 3 of 95 per cent, spirit). Oleic acid is not thrown out 

 even by the addition of 2 *2 cc. of a mixture of equal volumes of 

 glacial acetic acid and water to 3 cc. of alcoholic solution. Under 

 these circumstances stearic acid would be completely separated. 

 (See 16, 131.) 



131. The separation of resins from fat-acids in soap-analysis has 

 formed the subject of communications from Jean, 2 Barfoed 3 and 

 Gladding. 4 The following particulars are taken from Barfoed : 



a. Stearic and palmitic acids are soluble in hot 70 per cent, 

 spirit, but separate out on standing twenty-four hours in a cool 

 place. Coniferous resin (abietic acid) dissolves in 1 parts of cold 

 spirit of the same strength, but is precipitated on adding water 

 containing hydrochloric acid. 



b. If a mixture of the same fat-acids with resin is boiled with 

 7 volumes of 30 per cent, spirit, to which 1 volume of an aqueous 

 solution of carbonate of soda (1 to 3) has been added, both resin 

 and fat-acid dissolve. On cooling, the soap produced from the 

 fat-acids separates out, whilst the resinate of soda remains in 

 solution. The fat-acids may be obtained from the precipitate by 

 filtering off, washing with alcoholic carbonate of soda solution and 

 decomposing with hydrochloric acid, whilst the filtrate yields the 

 resin on treatment with an acid and shaking with ether. 



c. On adding a solution of 1 part of chloride of calcium in 15 

 of 80 per cent, spirit to a hot solution in spirit of the same 

 strength, and cooling, the calcium salts of both fat-acids separate 

 out, whilst that of the resin acid remains in solution. 



d. If stearic and palmitic acid and resin are dissolved in soda, 

 the solution evaporated to dryness, powdered and extracted with a 



1 Zeitschr. f. anal. Chem. xviii. 622, 1879 (Journ. Chem. Soc. xxxiv. 1011). 



2 Polyt. Journ. ccvii. 1873 (Journ. Chem. Soc. xxvi. 195). 



3 Zeitschr. f. anal. Chem. xiv. 20, 1875 (Journ. Chem. Soc. xxix. 771). 

 Compare also Gottlieb, Poliz. chem. Skizzen, Leipzig, 1853 ; and Sutherland, 

 Chem. News, 1866, 185. 



4 Chem. News, xlv. 159, 1882. 



