Phelps and Eddy — Purification of Esters. 255 



— ester, alcohol and water — of the second 100 cm3 Claisen flask, 

 connected in the manner just given for distilling under dimin- 

 ished pressure, were carefully fractionated by heating the 

 Claisen flask in a water bath raised slowly to 60°, which tem- 

 perature was maintained for 15 minutes after the manometer 

 showed a pressure of 15 mm , and the ester distilled in the 

 usual manner into the flask, weighed, in some instances, alone, 

 in others, with the short tube held in place during distillation 

 by the rubber stopper, and the weight of ester determined. 



In all the experiments in the table except (3), (4), (8) and (10) 

 the potassium carbonate was ignited before attempting to 

 neutralize the esters mixed with organic and mineral acids. 

 In experiments (3), (4), (7), (8), (9) and (10), both in distilling 

 and redistilling the ester from the Claisen flasks the process 

 was carried out in flasks where the shortened side-neck tube 

 of the first flask was held with a glass tube through a rubber 

 stopper. It seems evident that igniting freshly the potassium 

 carbonate is unnecessary. Further, the jointed apparatus does 

 not appear to diminish the small loss of ester. 



The purity of the product obtained was shown by redistilling 

 the recovered ester at atmospheric pressure, when it was found 

 that the entire portion distilled within a fraction of a degree. 



From an inspection of the results obtained it is clear that 

 diethyl succinate, diethyl malonate and ethyl benzoate may be 

 freed from small amounts of mineral and organic acids, when 

 alcohol is present, by heating suitably with dry potassium car- 

 bonate under diminished pressure, and that the total product 

 obtained in this way, fractionated under diminished pressure, 

 gives a satisfactory indication that ester is not lost in consider- 

 able amounts. The losses in the treatment of the masses of 

 75 grm. each of pure ester as in the former work from this 

 laboratory, referred to above, amounted to 0'6 grm. in the 

 case of the recovery of succinic ester, to 1"25 grm. in the case 

 of malonic ester, and to 0*25 grm. in the case of benzoic ester. 

 While the loss in the recovery of ethyl benzoic ester by neu- 

 tralizing as described with dry potassium carbonate is slightly 

 greater than by shaking out with ether, the loss in recovering 

 diethyl succinic ester is somewhat less, and the loss in recover- 

 ing diethyl malonic ester is much less than by shaking out 

 with ether. But, even in the case of ethyl benzoic ester, the 

 treatment with dry potassium carbonate is to be preferred of 

 the two procedures, both on account of the greater ease in 

 manipulation and on account of the saving in expense, since 

 dry potassium carbonate accomplishes the purpose of the 

 aqueous sodium carbonate and shaking out with ether. 



Obviously it is possible to neutralize the acid impurities pres- 

 ent with these esters with dry potassium carbonate completely 



