286 Phelps and Eddy — Hydrobromic Acid. 



estimated. The amount of mineral acid left in the esterifi- 

 cation flask and neutralized with sodium carbonate in the 

 process of recovery of the crude ester in the experiments (1) 

 and (2) of Table III and (1) of Table I was also estimated. 

 This was done by acidifying the sodium carbonate wash water 

 with nitric acid, the precipitated benzoic acid w T as filtered off 

 and washed with cold water and the halogen acid in the filtrate 

 was determined gravimetrically as the silver salt. In experi- 

 iment (1) of Table I the total amount of hydrobromic acid in 

 the residues was found to be 1*34 grm., of which 0*07 grm. 

 was in the alcoholic distillate. In this experiment 4*4 grm, 

 of hydrobromic acid were used, leaving 3*06 grm. of hydro- 

 bromic acid, which presumably formed ethyl bromide. In 

 experiment (4) of Table II the amount of hydrobromic acid 

 found in the alcoholic distillate was 0*0102 grm. In experi- 

 ment (24) of Table II the amount of hydrobromic acid found in 

 the alcoholic distillate was 0*0048 grm. In diluting the first 

 portion of the alcoholic distillate ethyl bromide was found 

 present in such amount as to make the resulting liquid turbid. 



These experiments show first that at a temperature 85°-90° 

 about seventy-five per cent of the hydrobromic acid has reacted 

 to form ethyl bromide ; second, that the hydrobromic acid 

 which remains as such accumulates in the ester ifi cation flask ; 

 and, third, that zinc bromide has a catalytic effect upon the 

 action of ethyl alcohol and hydrobromic acid, as might have 

 been anticipated. 



Similarly, in experiment (1) of Table III the total residues 

 of hydrochloric acid were found and amounted to 1*84 grm., 

 of which 0*110 grm. were found in the alcoholic distillate and 

 1*455 grm. in the esterification flask, leaving 0*185 grm. from 

 a total of 2*025 grm. of hydrochloric acid taken w T ith the alco- 

 hol, which reacted presumably to form ethyl chloride. In exper- 

 iment (2) of Table III the total hydrochloric acid found in all 

 residues was 1*485 grm., of which 0*615 grm. was in the alco- 

 holic distillate and 0*595 grm. was in the esterification flask, 

 leaving 0*54 grm. from a total of 2*025 grm. taken in the alco- 

 holic mixture. In experiment (3) of Table III the hydro- 

 chloric acid found in the alcoholic distillate was 0*0019 grm., 

 and in (4) of the same table 0*0017 grm. was found in the 

 alcoholic distillate. 



The evidence from these experiments proves that, at a tem- 

 perature of 100°-110°, about ten per cent of the hydrochloric 

 acid present has reacted to form ethyl chloride. At the higher 

 temperature of 125°-150°, a larger amount, about twenty-five 

 per cent, is used in this way. With hydrobromic acid of simi- 

 lar concentration, this sort of action, at the lower temperature 

 of 85°-90°, goes on to a much larger extent. Thus, in experi- 



