Substituted Aliphatic Acids. 



60 7 



immediately neutralized by the excess of acid present. In this 

 way a very sharp end-point was obtained, since in acid of such 

 dilution the velocity of decomposition of any ester is negligible. 

 It seems probable that irregularities in constants caused in this 

 way are very slight, especially in view of the fact that uniform 

 procedure was adopted for all measurements. The principal 

 cause of irregularities is the difficulty of titrating accurately with 

 such dilute solutions in the presence of relatively large amounts 

 of salts of the organic acids. On the whole, however, reason- 

 ably good constants were obtained even in cases where the 

 reaction proceeded with considerable velocity. 



Calculations were made by the use of the titration formula* 

 for reactions of the second order. 



K = 



4343 -**T, 



[log T 



log (T.-TJ 



loo- T 



log (T - T )] 



T is the amount of HC1 consumed by the excess of NaOH 

 at the time t. T is the initial titration and T x the titration 

 value of the excess of NaOH at the end of the reaction. All 

 values of T were of course obtained indirectly by subtraction 

 of the quantities of barium hydroxide from the fifteen cubic 

 centimeters of acid employed. V is the volume of the pipette, 

 and N the normality of the hydrochloric acid in terms of which 

 the reaction was measured. 



In the tables are given the values of K and of the periods in 

 minutes over which the reactions proceeded with measurable 

 velocity. 



Table I. 



Eeaction at C 



Ester. 



Time. 



K 



Ethyl 

 acetate 



300 

 'T24 

 1-21 

 1-20 

 144 

 143 

 141 

 146 



147 

 149 



Ethyl 

 glycollate 



35 

 13-8 

 13-5 

 (9-7) 

 12*3 

 12-6 

 12*4 



Ethyl 



methyloxy 



acetate 



25 



36*7 

 39*5 

 40-3 

 37-7 

 36*4 

 33-7 

 30'5 



Ethyl 



ethyloxy 



acetate 



25 



13'8 



18-6 



16'8 



15*8 



14-5 



15-4 



Ethyl 



propyloxy 



acetate 



25 

 12-6 

 12-8 

 13-8 

 12-9 

 13-0 

 11-4 

 12-3 



12-7 

 12-9 



Averages.. 147 12-9 36*4 15*9 



Averages.. 149 12*8 374 15*2 



(duplicate) 



* Findlay, Practical Physical Chemistry, p. 243. Ostwald-Luther, loc. cit. 



