374 Phelps and Hubbard— Est-erification of Succinic Acid. 



tious of the acid. In experiments (21) and (22) after the treat- 

 ment for esterification, as given earlier, was completed, all low 

 boiling point material, chiefly alcohol, water, and hydrochloric 

 acid, was removed from the ester in the sideneck flask lyy a 

 vacuum fractionation, carried out by heating the flask in a 

 waterbath finally at 60° with the pressure on the manometer 

 registering 15 mm , this pressure and temperature being main- 

 tained fifteen minutes. The material in the flask was then 

 treated with fresh alcohol and hydrochloric acid in amounts 

 given in the table in gaseous form as in the first half of the 

 experiment. Pure succinic acid was used in case of (21), and 

 commercial acid in case of (22). This process of removing traces 

 of water by the intermediate vacuum distillation from the 

 mixture containing the ester is obviously very effective, and 

 the yield of experiment (21) is the best of the entire suite. 

 Indeed if it be recalled that the losses inherent in the processes 

 of obtaining the pure ester are a fraction more than a gram, 

 it is seen that all of the acid taken appears as ester except a 

 portion as small as 0*30 of a gram. 



So it appears that while high purity of the succinic acid and 

 the alcohol, the proportion of the hydrochloric acid, the time 

 of the reaction, are all influential factors in the process of 

 forming the ethyl ester, the thing most important in obtaining 

 a high yield is the removal of the water as it is formed in the 

 reaction ; and we have found that this may. be done most 

 easily and very effectively by passing the vapor of alcohol 

 charged with a small proportion of hydrochloric acid into a con- 

 tinuously distilling mixture of succinic acid and alcohol also 

 charged with hydrochloric acid. By thus acting with a total 

 volume of 300 cni3 of the alcohol charged with 1*25 per cent of 

 hydrochloric acid upon 50 grins, of succinic acid, the yield in 

 action of five hours reached 97 per cent of the theory, while 

 this time of action was cut in two and the yield at the same 

 time slightly increased to 97*7 per cent by interpolating in the 

 process a vacuum distillation to remove water more effectively 

 from the reacting mixture. 



Even if the usually small amounts of ester which pass to 

 the distillate are disregarded in the process of recovery, the 

 yield of the process in its simpler form is still 20 per cent 

 higher than that of any other described procedure known to 

 us for making the ethyl ester of succinic acid by the inter- 

 action of the acid and alcohol. 



