Phelps, Palmer and Smillie — Ester Formation. 291 



The catalyzers studied were the acid sulphates of potassium, 

 ammonium, sodium, pyridine, and aniline. These were made, 

 in the case of the inorganic salts, by heating the anhydrous 

 neutral sulphates with the proper proportions of sulphuric acid 

 in a porcelain crucible until the mass fused together, then 

 grinding in an agate mortar. The organic sulphates were 

 made by adding sulphuric acid in the proper proportions to 

 the pyridine or aniline in the esterification flask in the case of 

 the benzoic acid ; in the case of the succinic acid, however, they 

 were mixed before being put into the flask. The sodium sul- 

 phate, the potassium sulphate, the pyridine, and the aniline 

 were the pure anhydrous material of commerce. Pure ammo- 

 nium sulphate was prepared by treating in water solution with 

 an excess of sodium hydroxide the ammonium salt precipitated 

 by the action of hydrochloric acid on cyanacetic ester under the 

 conditions shown in an earlier paper* in this Journal and 

 catching the ammonia evolved on distillation in dilute sul- 

 phuric acid. The salt obtained by evaporating the solution, 

 neutral to litmus, was recrystallized and dried. 



The proportions of catalyzers used were chosen such that the 

 amount of the sulphuric acid used to form the acid sulphates 

 here was the same amount, or a multiple or submultiple of the 

 amount, used as catalytic agent in the former paperf on the 

 esterification of benzoic acid ; that is to say, the concentrations 

 of the hydrogen ions present during the esterification in the 

 two researches were in molecular ratio. 



Of the catalyzers studied, the acid pyridine sulphate was the 

 only one which seemed to go entirely into solution during the 

 esterification. Of the others, the acid ammonium sulphate was 

 perhaps the most soluble, but it did not go entirely into solu- 

 tion, even in the case of the smallest amount which was used. 



The succinic ester in experiments (1) to (7) inclusive of Table 

 I was recovered, according to previous work,;]: by treating the 

 crude ester in the esterification flask with an excess of solid 

 potassium* carbonate, and heating the flask fitted up for a 

 vacuum distillation with a 100 cm3 Claisen flask as receiver, 

 under a pressure of 15 mm , to 100°-110° on an acid potassium 

 sulphate bath until no more carbon dioxide was evolved. The 

 ester was then distilled under the same pressure — 15 mm — , 

 allowing a stream of cold water to strike the receiver continu- 

 ously during the distillation. The distilled product was then 

 redistilled, the lower boiling impurities being first removed by 

 raising the temperature of the flask to 60° under a pressure of 

 15 mm , before the succinic ester was distilled and weighed. The 

 succinic ester in the remaining experiments of Table I and the 



* This Journal, xxvi, 258. f This Journal, xxv, 39. 



X This Journal, xxvi, 253. 



