46 Phelps and Osborne — Esterification of Benzoic Acid. 



evident from a comparison of (17) and (18) with (12), and of (20) 

 with (23). If certain concentrations of zinc chloride and 

 hydrochloric acid are taken with a suitable amount of alcohol 

 it is possible to obtain yields of ester" either theoretical or very 

 nearly so, as is seen in (12), (13) and (16). With greater con- 

 centrations of mineral acid and the same amount of zinc 

 chloride more alcohol and longer time for the esterification are 

 required. With a smaller amount of zinc chloride more alcohol 

 and a longer time are necessary to obtain equalW desirable 

 results. 



From a comparison of the results in series A with those of 

 series B it is clear that the alcoholic mixture made of alcohol 











Table III. 



















A 





Benzoic ester 



g 



enzoic 

 acid 



Alcohol 



H 2 S0 4 



Eeaction 

 tinie 





_^_ 







Theory 



Found 





No. 



grm. 



cm 3 



grm. 



hr. 



mi. 



grm. 



grm. 



per cent 



( 1) 



50 



200 



0-5 



2 



20 



61-48 



56-14 



91-3 



( 2) 



50 



300 



0-5 



2 



30 



61-48 



59-82 



97-3 



( 3) 



50 



200 



1 





45 



61-48 



50-59 



82-3 



( 4) 



50 



200 



1 



2 



30 



61-48 



61-15 



99-5 



( 5) 



50 



300 



1 





45 



61-48 



53-43 



86-9 



( 6) 



50 



100 



2 



2 





61-48 



55-80 



90-8 



( 7) 



50 



200 



2 





45 



61-48 



60-18 



97-9 



( 8) 



50 



200 



2 



3 





61-48 



61-52 



100-0 



( 9) 



50 



200 



2 



3 



15 



61-48 



61-83 



100-0 



(10) 



50 



120 



10 



1 



45 



61-48 



58-38 



95-0 



(ID 



50 



200 



25 



5 



20 



61-48 



57-81 



94-0 



(12) 



50 



200 



50 



3 





61-48 



57-81 



94-0 



(13) 



50 



200 



50 



3 





61-48 



57-88 



94-2 



(14) 



50 



100 

 100 



20 



2 



3 





61-48 



59-95 



97-5 



(15) 



50 



300 



2 



3 



B 



61-48 



58-00 



94-3 



(16) 



50 



300 



2 



3 





61-48 



57-98 



94-3 



(17) 



50 



300 



50 



3 





61-48 



5311 



86-4 



of 88-8 per cent purity does not esterify the benzoic acid as 

 completely as does the purer alcohol. The time during which 

 esterification goes on is also a factor. By comparing (20) and 

 (21) it is seen that the yield of ester is increased 5 per cent by 

 increasing the time during which the reaction was allowed to 

 take place. It is clear here, too, that the increase, within 

 limits, in the proportion of zinc chloride to the other reagents 

 produces a larger amount of ester, as may be seen by compar- 

 ing (18), (19) and (22). 



