Sir B. C. Bi'odie on the Action of Electricity on Gases. 471 



mixture. The interior and exterior of the tube were respectively 

 connected with the terminals of a powerful Ruhmkorff's coil. The 

 electrized gas, after its passage through the induction-tube, was 

 collected, in a gas-holder of peculiar construction, over concentrated 

 sulphuric acid. It may be thus preserved for several hours without 

 sensible variation in its properties. 



The principle employed for the measurement of the gas in which 

 it was desired to estimate the changes in volume produced by the ex- 

 periment, was the principle of pipette-measurement which has been 

 so successfully employed by chemists for the measurement of liquids. 

 In this way a considerable volume (say from 2.50 to 300 cub. centims.) 

 may be measured with facility and precision. A definite volume of 

 gas was thus always operated upon. 



The gas having been measured in the pipette was drawn over by 

 means of a mercurial aspirator, an instrument which served the 

 double purpose of an aspirator and measuring-apparatus. The 

 principle of this aspirator was that originally employed in the apparatus 

 of Regnault for measuring the volumes of gases, namely the esti- 

 mation of the pressure and temperature at which the gas occupied 

 a known space, from which the volume of the gas at standard 

 temperature and pressure was calculated. By means of this ap- 

 paratus a change in the volume of the electrized gas, to the extent of 

 about 1 part in 1000, could be accurately estimated; that is to say, 

 after the calibration of the apparatus, 1000 volumes of gas as mea- 

 sured in the pipette were found to measure 1000'7 volumes in the 

 aspirator. These numbers represent the errors of the experiment, 

 and any differences in the volume of the gas beyond this limit must 

 be considered to be due to the experiment to which the gas was 

 submitted. The pipette and the aspirator were placed on a table, 

 separated by an interval of about 8 or 1 inches. 



In Section II. the results are given of passing the electrized gas 

 through a solution of neutral iodide of potassium, also of heating the 

 gas, of passing the gas over metallic silver, copper, gold, aluminium, 

 and binoxide of manganese, and of the decomposition of a solution of 

 binoxide of sodium effected by the passage of the gas, a quantitative 

 estimation of the changes in the volume of the gas and the oxidation 

 effected being in all cases made. 



The precision attained in such experiments may be estimated by 

 the results of the measurement of the gas before and after its passage 

 through a solution of neutral iodide of potassium. As the mean of 

 eight concordant experiments, 100 cub. centims. of gas, as measured 

 in the pipette, were found after the experiment to measure 99*93 cub. 

 centims. in the aspirator. An oxidation was effected in the solution of 

 neutraliodide of potassium equivalent to 3*77 cub. centims. of oxygen; 

 that is to say, 3'77 cub. centims. of oxygen were thus removed from 

 the gas without an appreciable variation in its volume. The volume 

 of the gas thus absorbed by neutral iodide of potassium was in sub- 

 sequent experiments assumed as the unit to which other analogous 

 variations were referred. 



When the electrized gas is passed through a solution of binoxide 



