134 EXPERIMENT STATION. [Jan. 



tiouation apparatus. Heat is furnished by means of a linseed 

 oil bath, and suction bj a pump of any type, using a mercury 

 manometer to prove constancy of vacuum. The neck of the 

 flask from the shoulder to an inch or more above the side tul>e 

 should be wound with asbestos paper to prevent cracking, due 

 to sudden changes of temperature. The condenser should be 

 kept full of water, without circulation, to serve as a hot-water 

 jacket. The vacuum should be as high as the flask will safely 

 withstand, but above all uniform, otherwise the fractions are of 

 questionable value. The temperature range of an ester also 

 varies with the distance between surface of liquid and side tube. 

 At least one redistillation of like fractions is necessary. 



As the esters are very stable, more difficulty was experienced 

 in finding some means for their quantitative decomjoosition than 

 in any other portion of the work. Heating with mineral acids 

 hydrolizes the fatty acids very slowly, even under pressure. If, 

 however, the esters are first saponified ^ by heating over a naked 

 flame with twice their volume of glycerol and an excess of caus- 

 tic potash until all the alcohol is expelled, and then the result- 

 ing soap dissolved in water and heated on a water bath with a 

 slight excess of sulfuric acid, the separation is readily accom- 

 plished. This plan was suggested by the Lefi"mann-Beam sapon- 

 ification for volatile acids, and after extended trial proved the 

 most thorough and rapid means for decomposing the esters. 

 The resulting acid should be washed in a separatory funnel with 

 boiling water until clear, and the cake allowed to drain. As 

 previously stated, several crystallizations are necessary if a 

 crystalline product of satisfactory melting point and neutrali- 

 zation number is to be secured. When crude acids are employed 

 it is also advisable to crystallize at the outset to exclude a major 

 ])art of the unsaturated acids, which otherwise would prove 

 troublesome. 



To summarize : saturated fatty acids may be purified by dis- 

 tillation of the acids or their ethyl esters. The latter method is 

 less hazardous and easier to manipulate, although more steps 

 are required. Crystallization is a finishing rather than an ini- 

 tial process of purification. 



1 Observing the usual precautions given for the determination of insoluble fatty acids, Massa- 

 chusetts Agricultural Experiment Station, twenty-first report, p. 130 (1909). 



