40 Phelps and Osborne — Esterification of Benzoic Acid. 



phuric acid was the pure, concentrated acid of commerce, sp.gr. 

 1*84. The alcohol was charged with dry hydrochloric acid 

 by saturating in the cold a given weight of alcohol with a 

 known amount of dry hydrochloric acid, and then diluting to 

 definite concentration. Pure anhydrous zinc chloride was 

 melted and treated at the same time with hydrochloric acid 

 gas dried by means of sulphuric acid. 



In every experiment recorded in Table I alcohol alone or 

 alcohol charged with dry hydrochloric acid was boiled in a 

 500 cm3 round-bottomed flask, fitted with an outlet tube and a 

 separating funnel carrying a drying tube, and passed in vapor 

 at a uniform rate during the entire time to the bottom of 

 another 500 cm3 round-bottomed flask containing a definite 

 weight of benzoic acid and a definite volume — 40 c,n3 — of alco- 

 hol alone or charged with a definite weight of dry hydrochloric 

 acid as indicated in the table. The temperature of the mixture 

 in the flask in which esterification took place was kept between 

 100° and 110° by heating the flask in a bath of sulphuric acid 

 and potassium sulphate, and this temperature was indicated by a 

 thermometer dipping in the mixture and held in a three- 

 bored rubber stopper fitted to the second flask and carrying 

 also the glass tube for the introduction of the vapor. The 

 vapor liberated in the second flask passed by means of a 

 Hempel column, arranged as described in the paper to which 

 reference has been made, to a condenser and was collected as 

 the liquid distillate. 



In general, the mass of ester with its impurities was poured 

 into a separating funnel containing a little ice, the last traces 

 of the liquid being transferred from the flask to the funnel by 

 successive rinsings with ether. The impure ester in the funnel 

 was treated with an excess of dissolved sodium carbonate, and 

 the water solution was drained off from the supernatant mix- 

 ture. This mixture was washed once with a water solution 

 of sodium chloride of sufficient density to separate it easily 

 from the mixture. To recover any portion of the ester carried 

 along in the water solution of sodium carbonate and the wash 

 water containing sodium chloride, each solution was shaken 

 out separately three times with fresh portions of ether and 

 these were added to the mixture. These mixtures of ester in 

 the ethereal solutions were gathered in a 250 cm3 side-necked 

 flask connected with a 100 cm3 side-necked flask as a receiver in 

 the usual way for a vacuum distillation. The impurities of 

 lower boiling point, presumably composed chiefly of ether, 

 alcohol, and water, were removed from the benzoic ester by 

 allowing a gentle current of air to pass through the apparatus, 

 while the flask containing the ester solution was heated in a 

 water bath raised finally to 60° until the pressure shown 



