Phelps and Osborne — Esterification of Benzoic Acid. 43 



in the flask, as was done when the first masses of benzoic acid 

 were esterified. In case of experiments (14) and (15) the 

 vacuum fractionation was repeated, and a third portion of the 

 alcoholic mixture was driven as before into the esterifying 

 mass. 



It would seem from experiment (1) of series A of Table I that 

 under the conditions imposed the esterification of benzoic acid 

 with ethyl alcohol alone does not proceed far enough to pro- 

 duce benzoic ester in appreciable amounts. The presence of 

 hydrochloric acid as shown by the remaining experiments of 

 series A causes the esterification to proceed, but so large an 

 amount of it as 25 per cent is not advantageous if the time of 

 sending all vapors into the esterifying mass is the same in all 

 cases ; for, it was observed that on heating the alcoholic hydro- 

 chloric acid of so high concentration as 25 per cent only the 

 acid was driven over during the first part of the experiment, 

 and consequently the time of the action of the alcohol on the 

 benzoic acid was made correspondingly shorter. Results in 

 series B seem to indicate that removing by a vacuum fraction- 

 ation the water formed during the esterification that takes 

 place with a given alcoholic mixture driven more rapidly into 

 the flask containing the benzoic acid is not so efficient in pro- 

 ducing esterification as is allowing half that amount of alcoholic 

 vapor with the hydrochloric acid to act for the same interval. 

 This is shown by comparing (3) with (7), and (4) with (9) and 

 (10), although in the last cases the difference is not so marked 

 as perhaps might be expected from a consideration of the 

 amounts of hydrochloric acid introduced. The difference in 

 the yield where 25 per cent acid was used, in experiments (5) 

 and (13), is due probably to the difference in the times during 

 which the alcoholic mixture was passing into the flask contain- 

 ing the benzoic acid. Experiments (14) and (15) seem to 

 indicate that with the concentrations used, removing the water 

 a second time does not increase the efficiency of the process for 

 the same time of action, even though more of the alcoholic 

 mixture is used. This is seen by comparing experiments (12) 

 and (14). On comparing (13) and (15) it is seen that neither 

 increasing the amount of alcohol, lengthening the time beyond 

 three hours, nor removing the water a second time materially 

 helps esterification. It seems clear that the complete esterifica- 

 tion of a given mass of benzoic acid with ethyl alcohol and 

 hydrochloric acid would be a matter of some difficulty. 



All of the experiments of series A in Table II show the 

 action of zinc chloride in assisting the esterification of benzoic 

 acid with alcohol alone as well as with the same alcoholic mix- 

 tures used for the work given in Table I ; and in series B the 

 action of zinc chloride in ethyl alcohol of 88 "8 per cent purity 



