60 BOTANICAL GAZETTE [JULY 
all the dissociation in pyrogallol at 1/20 molecular concentration is 
due to H* dissociation and only one H dissociates, the H* con- 
centration is less than 0.000616 equivalent. If all three H’s dis- 
sociate it is less than 0.000616 3, or, in other words, the theoretical 
H™ concentration of the pyrogallol solution in the apparatus is 
between 107” and 107° or less than either. Because of BUNZEL’S 
statement (2, p. 28) that either fresh or old pyrogallol solution 
may be used it is worthy of note that a 1 per cent solution six 
months old required dilution to 3.5 and a two-thirds of 1 per cent 
solution to 2.33 times its original volume before it failed to give the 
red color with methyl orange, thus indicating for the two-thirds 
solution an H* concentration of 2.331075 or 107? (not 
allowing for increased dissociation with diJution). That is, by 
slow spontaneous oxidation the H* concentration of a two-thirds 
of 1 per cent solution of pyrogallol solution is increased in six 
months from less than 107333 to 1o~?-%. It follows that fresh 
pyrogallol solution should be made up for each experiment. In 
this connection it seems rather more than a coincidence that in 
BUNZEL’s experiment 6 (2, table VI, p. 28) fresh 1.0 per cent and 
o.1 per cent pyrogallol solutions gave, in a test only one hour long, 
respectively o.1 and 0.05 cm. higher negative pressure (greater 
oxidation) than similar solutions one year old. 
The reaction to phenolphthalein of the mixtures in the apparatus 
may be calculated from the data given in table III. For those 
containing extract of healthy bark, sample 17, it would be 
0.0+0.86+(4X0. 34) 
6 
0.37; for those containing extract of dis- 
0.0+0.38+(4X0. 34) 
: ee 
eased bark, sample 15, 0.29. The acidity 
of the once distilled water was found to be negligible. On account 
of the correspondence already observed between titration and 
indicator figures for both the pyrogallol solution and the extracts, 
the reaction of the mixtures in the apparatus may be taken to 
represent roughly the H~* concentration also until further work 
can be done. 
To test the effect of varying the acidity of the extract on the 
rate and total amount of oxidation, experiment 3 was set up, using 
