Mar. 38. igts Fatty Acids in Butter Fat 723 



EsTERiFiCATiON (fig. i). — Earlier investigators have indicated various 

 methods of esterification. Absolute alcohol with a mineral acid catalyzer 

 appeared the most practicable for analytical purposes and was adopted 

 tentatively. Between methyl and ethyl alcohols there was little choice, 

 except as to cost and convenience, although the methyl esters have a 

 somewhat lower boiling point. Ethyl alcohol was used exclusively. 



The preparation of dry ethyl alcohol substantially free from aldehydes 

 was found considerable of a problem. For dehydration neither metallic 

 calcium nor any quicklime from the usual sources proved efficient. A 

 granulated caustic lime containing about 95 per cent of calcium oxid was 

 eventually obtained from the manufacturers which would produce a dry 

 alcohol on the third distillation. 



Different schemes have been suggested for the removal of aldehydes, 

 such as oxidation with silver nitrate, potassium permanganate, or 

 potassium bichromate, polymerization with caustic alkali or fractional 

 distillation, and all were tried in some form or other. The following 

 process finally proved satisfactory and w^as adopted : 



Approximately 2 liters of alcohol w^ere fractionated in a water bath 

 over 600 to 700 gm. of caustic lime and 2 to 3 gm. of caustic soda. The 

 main portion of the distillate, the first and last being rejected, w^as refrac- 

 tionated twice in a similar manner over fresh lime and soda. The 

 rejected portions were united and retreated. 



Dry hydrochloric acid or concentrated sulphuric acid has been the 

 catalyzer almost invariably employed by different workers for esterifica- 

 tion. The former with a greater hydrogen-ion concentration is apparently 

 less efficient, gram for gram, than the latter, and is generally used in 

 larger amounts. This may be due in part to loss of hydrochloric acid 

 as ethyl chlorid by volatilization, but more likely to the dehydrating 

 effect of sulphuric acid. By using a larger quantity of alcohol, together 

 with certain chlorids, the yield of esters with hydrochloric acid may be 

 increased, as shown by Phelps. 



A considerable excess of alcohol is also required to insure the necessary 

 mass action irrespective of its dehydrating action. For esterif\ing 150 

 gm. of butter fat, 400 c. c. of absolute ethyl alcohol containing 8 gm. of 

 dry hydrochloric acid or 4 c. c. of concentrated sulphuric acid were 

 employed. This amount of alcohol furnished about 1 1 times that needed 

 for combination with the fatty acids. 



The use of a neutral solvent, such as ether, did not appear to accelerate 

 esterification and w^as omitted after a few trials. Butter fat diffused 

 rapidly through the acid alcohol on boiling, and the solution generally 

 cleared in a few minutes. Short boiling periods were tried, but 24 hours 

 were considered more reliable and adopted. 



Purification of esters. — After completing the esterification and 

 cooling the solution, the esters must be precipitated and freed from 

 mineral acid, glycerol, and excess alcohol. 



