18 



The Philippine Journal of Science 



1913 



Substituting 0.0223 for K 3 in (16), (17), (18), and (19), we 

 obtain, for K,, 0.00498, 0.005176, 0.005589, and 0.005489, respec- 

 tively. The mean of the five values of K is 0.00516. 



Now, putting t 2 =600, t x =305, x 2 =0.0861, and x 1= 0.067 in 

 equation II and applying Simpson's rule, we get t=311.47 min- 

 utes instead of 295 minutes, the observed value. Leaving K 3 as 

 it is and changing K 2 to 0.0053, we obtain for the same difference 

 between the values of x, 303.6 minutes, an error of 2.5 per cent. 



Plotting the values of x as abscissas and the values of 



K TZ1-1-K rz~l 2 as or ^ mates ' using K 3 =0.0223 and K 2 =0.0053, 



we obtain a smooth curve, which shows that the values of K 2 and 

 K 3 are at least very good approximations (fig. 2). We can 

 now test the accuracy of the constants by computing the values 

 of t from the area under this curve. For example, the area 

 under the curve from x=0.0516 to x=0.0861 gives 400.54 min- 

 utes instead of 415 minutes, an error of 3.5 per cent. 



Similarly, values of t computed from the curve between dif- 

 ferent values of x agree well with the observed values of t, 

 except for the first three values of x. The values of t from 

 x=0.04 and x=0.069, for instance, show a discrepancy of 25 per 

 cent. 



This greater discrepancy during the earlier part of the sapon- 

 ification is undoubtedly due to the excessive velocity of the 

 transformation as compared with the rate of solution. 



Table V. — Saponification of methyl salicylate with NaOH 0.09H Normal. 

 T=30° ± 0.1. Congo red indicator. 



t. 



X 



a — x. 



Kmono. 



t (inter- 

 polated 

 values) . 



K2, (when 

 K3=0.0223). 





 65 

 125 

 185 

 245 

 305 

 365 

 415 

 480 

 540 

 600 







0.0263 

 0. 0400 

 0.0516 

 0.0609 

 0. 0670 

 0. 0721 

 0. 0769 

 0. 0806 

 0.0830 

 0. 0861 



0.0944 

 0. 0681 

 0.0544 

 0.0428 

 0. 0335 

 0.0274 

 0.0223 

 0. 0175 

 0. 0138 

 0. 0114 

 0.0083 



0. 00218 

 0. 00194 

 0. 00186 

 0. 00184 

 0. 00176 

 0. 00176 

 0. 00176 

 0. 00174 

 0. 00168 

 0. 00176 























295 

 335 

 415 

 475 

 535 



0. 005489 

 0. 005589 

 0. 005176 

 0. 004540 

 0. 004980 

















Mean 



0. 005160 



