84 
SIE B. C. BEODIE ON THE ACTION OE ELECTEICITY ON GASES. 
of electricity, in the induction-tube into oxygen and carbonic oxide is concerned, the 
results of this experiment might, even at the time it was made by me, have reasonably been 
anticipated, not only from the circumstance that carbonic-acid gas is, as is well known, 
decomposed by the passage of the electric spark, but also that Plucker* had already 
observed (although I was unaware of the observation) that when the electric discharge 
was passed through rarefied carbonic-acid gas, the spectrum of the gas after a short time 
changed into the spectrum of carbonic oxide, and from this circumstance had inferred 
the decomposition of the gas. But the observations of this eminent investigator were 
made under very different circumstances to mine ; and he was not cognizant of the forma- 
tion of ozone, which was the critical point of my experiment, and a result which could 
not have been ascertained by his method of observation. 
The experiment having failed in its immediate object was for a time laid aside by me. 
Subsequently, however, I reverted to it under a somewhat modified form. It occurred 
to me, instead of mixing oxygen with carbonic acid, to endeavour to generate in the very 
atmosphere of the carbonic acid itself, by the electric decomposition of the gas, the 
requisite amount of oxygen. I passed, therefore, pure and dry carbonic acid through 
the induction-tube, and examined the gases resulting from its decomposition, estimating 
the ozone by the titre of the gas, and also the oxygen and carbonic oxide formed. This 
examination at once convinced me of the importance of the experiment in reference to 
the problem of the isolation of ozone, and became the foundation of the following 
research, which has gradually been extended in more than one direction. 
Section I. 
The subject will be conveniently considered in two divisions. 
I will first lay before the Society the results of four experiments, in which the quan- 
tities were carefully measured, which may serve to define the general features of the 
decomposition and the methods of operation. 
A measured volume of carbonic-acid gas was passed through the induction-tube and 
there submitted to the electric action. On quitting the tube the gas traversed a bulb 
containing a solution of neutral iodide of potassium, the decomposition in which afiorded 
a measure of the ozone present in the gas. The gas was then passed into a bulb con- 
taining a strong solution of caustic potash, which absorbed the carbonic acid, while the 
oxygen and carbonic oxide were collected in it. 
The carbonic acid was made, in the usual way, from pure marble and dilute hydro- 
chloric acid in a (so called) Kipp’s apparatus. Having been washed with water and 
dried by passing through a system of tubes containing sulphuric acid and pumice imbued 
with sulphuric acid, the gas was collected in a sulphuric-acid gas-holder. A description 
of this gas-holder and of the other apparatus here employed for the collection of and 
measurement of gases is given in my previous paper, to which the reader is referred for 
information on the subjectf . The carbonic acid before its passage through the induction- 
* Pogg. Ann. vol. Cv. p. 82. f Philosophical Transactions, Joe. cit. p. 437. 
