Sill B. C. BRODIE ON TIIE ACTION OF ELECTRICITY ON GASES. 
459 
of the gas through the solution of hydriodic acid contained in one of the small bulbs 
previously described, and estimating the oxidation effected with a standard solution of 
hyposulphite of soda in the usual manner. A strong solution of hydriodic acid invari- 
ably contains a certain amount of dissolved iodine ; this amount was similarly estimated 
before the experiment in a quantity of the solution equal to that employed in it, and the 
number of cub. centims. of hyposulphite of soda employed in this titration was deducted 
from the number of cub. centims. of the same solution employed in the final titration. The 
difference represents the oxidation effected. The hydriodic acid was made of a definite 
strength by suspending in water a weighed quantity of iodine, and passing through the 
solution a current of sulphide of hydrogen, the acid being purified in the usual manner, 
a method sufficiently exact for the object in view. 
The solution of hydriodic acid employed was measured, in all cases, in a small pipette 
of the same capacity, namely about 15 cub. centims. This quantity will be here 
termed a bulb of the solution. 
The following experiments were made in the way described at a temperature of 18° C. 
I. 16 cub. centims. of the solution contained about one gramme of iodine in the form 
of hydriodic acid ; a bulb of this solution required for titration before the experiment 
0-72 cub. centim. of the standard solution of hyposulphite. After the passage of the 
oxygen, the bulb of hydriodic acid required for titration 1 cub. centim. of the same 
standard solution, which gives 0-28 cub. centim. of hyposulphite as equivalent to the 
oxidation effected by the pipette of pure oxygen. One cub. centim. of the hyposulphite 
employed was equivalent to 0-0002814 gramme of oxygen. The oxygen therefore 
operative in the experiment for the decomposition of the hydriodic acid was certainly 
not more than -000093 gramme. It was useless to attempt to follow the oxidation 
beyond this point. 
II. 8 cub. centims. of the solution contained one gramme of iodine ; the bulb of solution 
before the experiment required for titration T4 cub. centim.. of hyposulphite and after 
the passage of the gas in two experiments 3-25 and 4 cub. centims. of the same. Taking 
the mean of these two experiments, 3 - 62 cub. centims., and deducting T4 cub. centim., 
we have 2-22 cub. centims. of the standard solution of hyposulphite of soda as the 
measure of the oxidation. 
III. 4 cub. centims. of the solution contained one gramme of iodine in three experi- 
ments: the “ titres” after the experiment were respectively 5, 7 - 5, and G‘75 cub. centims. ; 
the “ titre” before the experiment was 2" 8 cub. centims., and the mean oxidation effected 
was equivalent to 3-61 cub. centims. 
IV. 2 cub. centims. of the solution contained one grain of iodine ; the “ titre” after the 
experiment was in three determinations respectively 9-75, 9-75, and 10 cub. centims., 
and before the experiment 5*75, the oxidation effected being equivalent to 4-0S cub. 
centims. 
Y. In the case of a very strong solution of hydriodic acid, of which 1 cub. centim. con- 
tained one gramme of iodine, 22-75 cub. centims. of hyposulphite were required for 
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