Phelps and Eddy — Hydrobromic Acid. 



283 



similar to that given in the former paper in this Journal on the 

 esterih'cation of benzoic acid to which reference has been made. 

 In brief the treatment consisted in heating at a definite tem- 

 perature a given weight of benzoic acid in the presence of a 

 small amount of alcohol with a certain amount of hydrobromic 

 or hydrochloric acid, or with an alcoholic solution of hydro- 

 bromic or hydrochloric acid, and zinc bromide or chloride in 

 definite amount. Into this mixture a known amount of alcohol 

 and hydrobromic or hydrochloric acid in definite amount was 

 driven at a uniform rate in vapor condition. The vapor issuing 

 from the flask in which the esterification took place was frac- 

 tioned by passing through a Hempel column attached to an 

 ordinary condenser. It has been shown in the earlier paper 

 that benzoic ester is retained completely in the flask in which 

 the benzoic acid is esterified. The ester was isolated in pure 

 condition by shaking out the mixture of the crude product with 

 ether, treating with sodium carbonate, and distilling under 

 diminished pressure in the manner described in the earlier 

 work on benzoic ester. 



It appears from an inspection of the results recorded in Table 

 I that hydrobromic acid as a catalyzer varies in its efficiency 

 according to its concentration, and according to the temper- 

 ature at which esterification takes place. This is seen in com- 

 paring experiments (1) with (10) and (1) with (5), or (10) with 

 (12) and (13). It is also clear that in comparing (8) with (9) 

 that the rate of flow of a given amount of alcoholic mixture 

 is of influence. A certain amount flowing rapidly is able to 

 esterify 10 per cent less benzoic acid than half that amount of 

 alcohol even in shorter time, as is seen by comparing (4) with 











Table I. 













Ben- 



Alcohol 





Time of 



Benzoic ester 





zoic 



with ttt?^ 



Tempera- 

 ture 



Q(jj:ir»-n 





A 





No. 



flcid. 











Theory 

 grm. 



Found 

 grm. 



' 





grm. 



• cm 3 



per ct. 



hrs. 



min. 



per ct. 



( 1) 



50 



200 



2-77 



85°- 90° 



2 



10 



61-48 



41-18 



66 98 



( 2) 



50 



200 



2-77 



90° 



1 



55 



61-48 



39-45 



64-17 



( 3) 



50 



200 



2-77 



100° 



2 



35 



61-48 



29-30 



47-66 



( 4) 



50 



200 



2-77 



100°-110° 



1 



45 



61-48 



27-00 



43-92 



( 5) 



50 



200 



2-77 



100°-120° 



3 



15 



61-48 



26-40 



42-94 



( 6) 



50 



200 



2-77 



125°-130° 



1 



55 



61-48 



17-70 



28-79 



( 1) 



50 



200 



2-77- 



125°-140° 



2 



5 



61-48 



15-58 



25-34 



( 8) 



50 



400 



2-77 



100° 



2 



5 



61-48 



20-31 



33-03 



( 9) 



50 



400 



2-77 



100° 



4 



25 



61-48 



35-96 



58-49 



(10) 



50 



200 



27-74 



85°- 90° 



3 



__ 



61-48 



56-05 



91-17 



(H) 



50 



200 



27-74 



90°-100° 



3 



50 



61-48 



50*96 



82-89 



(12) 



50 



200 



27-74 



90°-100° 



3 



_. 



61-48 



51-75 



84-17 



(13) 



50 



200 



27*74 



100° 



3 





61-48 



41-05 



66-77 



