458 
SIE B. C. BRODIE ON THE ACTION OE ELECTRICITY ON GASES. 
Section III. 
According to the statements of Andrews and Tait, the action of ozone upon an acid 
solution of iodide of potassium is, as regards the amount of oxidation effected, identical 
with its action upon a neutral solution of iodide of potassium. “ In some of the expe- 
riments the solution of iodide of potassium was slightly acidulated, in others it was 
neutral but “ the results were the same whether the solution was taken in the neutral 
or in the acid state”*. The method is not mentioned by which a comparison was effected 
between these results ; but the assertion is probably to be explained by the circumstance 
that these chemists experimented only with very dilute solutions of hydriodic acid, in 
which case the difference between the two oxidations, although by no means imper- 
ceptible, may not have been appreciated by their method of estimation. Out of many 
comparative experiments in no single case have I found the two oxidations to be 
identical. Meissner, on the other hand, who detected the essential difference in the 
case of the two oxidations, has fallen into an error of a different order, inferring the 
oxidation effected in the neutral iodide of potassium to be an altogether incorrect mea- 
sure of the ozone contained in the electrized gasf. I shall hereafter recur to his expe- 
riments on this point. 
The following experiments were among the first made by me as to the quantitative 
reactions of ozone, and were undertaken before the construction of the apparatus for 
exact measurement previously described, which accounts for some deficiencies in them. 
The volume of gas before the experiment was measured in a gas-pipette, into which 
the gas was passed from a sulphuric-acid gas-holder substantially of the same con- 
struction as that previously described ; the actual capacity of this pipette was 265’44 
cub. centims., and the pipette contained a volume of gas which, at the temperature 
and pressure at which the experiments were made, was in round numbers equal to 250 
cub. centims. at 0° C. and 760 millims. pressure. This volume does not in any tvay appear 
in the result of the experiment, and I shall speak of the volume of gas employed simply 
as a pipette of the electrized gas : this volume is assumed to be the same in consecutive 
experiments, which is not exactly true ; for although the barometer may be considered 
constant for the short interval of the experiments, the temperature of the gas was 
subject to slight variation : this variation in extreme cases amounted to as much as 1° C. 
I have taken no cognizance of this point in the calculation of the experiments, as it 
could only affect the results to the extent of part, whence the error in the calcu- 
lated result would appear only in the second decimal place, and be inappreciable. 
The investigation of the action of ozone upon hydriodic acid is complicated by the 
analogous decomposition effected by the oxygen with which the ozone is invariably 
associated ; in weak solutions of hydriodic acid this latter oxidation is extremely minute, 
but in strong solutions great errors would arise if it were not taken into account. 
The oxidation effected by the passage of a pipette of oxygen through a solution of 
hydriodic acid of a known degree of concentration was determined by passing a pipette 
* Philosophical Transactions, 1860, vol. cl. p. 121. 
t Meissxer, ‘Ncue II nt ersuchun gen uber den. elektrisirten SauerstofF,’ 1869, p. 82. 
