H. G. Thornton 



267 



the buffer solution standards. Where they differ from ours the " smoothed " 

 curve readings, given by Gillespie, are plotted in broken line beside our 

 readings. It will be seen that the two series agree closely in the case of 

 Brom Thymol Blue, but that there is a constant disagreement of about 

 0-05 pH on the alkaline side in the case of Phenol Red and of about 



8-5 



84 



8-3 



8 2 



8 1 



80 



79 



7-8 



7-7 



7-6 



7-5 



7-4 



7-3 



i 7-2 



I 71 



: 70 



I 6-9 



I 6-8 



?6-7 



i 66 



! 6-5 



6-4 



6-3 



62 



61 



60 



5-9 



5-8 



5-7 



5-6 



5-5 



Phenol Red 



I. I ^—1 I -I I 1 



8:2 7;3 6:4 5:5 4;6 3:7 2:8 

 Fig. 12. Drop ratios. (Acid indicator : alkaline indicator.) 



0-1 pH on the acid side, with Brom Cresol Purple. It is considered 

 probable that this is due to slight differences in the samples of indicator 

 used in the two cases. 



The smoothed curves thus experimentally obtained were used in 

 making the readings of ^H value in the work described below. 



