136 MASS. EXPERIMENT STATION BULLETIN 166. 



Limit of error, 0.05 per cent. 



Synopsis of Reaction. — Saponification of the fat with alcohoUc potash. 



Evaporation of the alcohol and dehydration of the soap. 



Extraction of the unsaponifiable matter with ethjd ether. 



Purification of the extract. 



Supplementary Notes. — In terms of the definition, the components of 

 unsaponifiable matter do not form water-soluble compounds on boiling 

 with potassium hydroxide. They are largely soluble, however, in the soap 



Fig. 4. — Ether extraction apparatus employed in the determination of unsaponifiable 



matter. 



solution, which is a factor to be noted in their separation by ethyl ether 

 from water or dilute alcoholic solutions. Furthermore, water hydrolyzes 

 neutral soaps, and alcohoHc solutions containing less than 50 per cent, 

 alcohol are unrehable for the same reason, as described under "Acid 

 Number." Soaps are soluble in moist ether. The extraction of un- 



