4 DR. ANDREWS ON THE CONSTITUTION AND PROPERTIES OF OZONE. 
oxygen gas was determined only for the purpose of ascertaining its relation to the 
ozone produced. 
The mixture of oxygen and ozone, having been perfectly desiccated in its passage 
through the long tube CC'C", enters the vessel D, where the ozone is decomposed, 
iodine being set free and caustic potassa formed, which latter, combining with the 
free hydrochloric acid, forms chloride of potassium. If a neutral solution of iodide 
of potassium is employed, the reaction is more complicated ; for, wdiile the greater part 
of the iodine is set free as before, and dissolves in the excess of iodide of potassium, 
iodate of potassa and caustic potassa are at the same time formed. Whether the 
solution be taken in an acid or neutral state, the final result is in this respect always 
the same, that the active oxygen enters into a chemical combination in the vessel D, 
and increases the weight of the liquid contained in that vessel. 
The increase in weight of the vessels D and E will give the entire weight of the 
ozone, whether that body be allotropic oxygen, or an oxide of hydrogen. On the 
former supposition, the decomposition of the iodide of potassium will result in the 
substitution of oxygen for iodine, both remaining in D, while the sulphuric acid in E 
will retain the moisture which would otherwise be swept away by the current of dry 
gas; on the latter, ozone will become resolved into water and oxygen, both of which 
will be retained in the vessels D and E. Now by determining the amount of free 
iodine in the iodide of potassium solution at the end of the experiment, the amount 
of active oxygen by which it has been displaced may be easily calculated ; and on 
comparing this with the increase in weight of the vessels D and E, it will at once be 
seen whether ozone be a peroxide of hydrogen yielding water in its decomposition. 
Two experiments of this kind were performed by Baumert ; in tlie first, the 
increase in weight of the apparatus amounted to 0‘0133grm., and the weight of the 
oxygen, as calculated from the iodine set free, to O’OOSl grm. ; in the second, the 
same quantities were respectively 0'0149 grm. and 0’00989 grm. The iodide of 
potassium was employed in the state of a neutral solution, and the iodate of potassa 
was subsequently decomposed by the addition of a little hydrochloric acid. 
It was from these results that Baumert inferred that the ozone which accompanies 
oxygen obtained by the electrolysis of water, is an oxide of hydrogen having the for- 
mula HO 3 ; and this conclusion, deduced from experiments which were devised with 
great skill and executed with care, has, in Germany at least, received very general 
assent. 
Having, as already mentioned, found, on a repetition of these experiments, that a 
different expression resulted for the composition of ozone from every new trial, I 
instituted a diligent search into all the circumstances of the experiment, and at last 
succeeded in referring the irregularities to the presence of a small, but appreciable 
quantity of carbonic acid, which, unless very great piecautions be taken, is always 
present in electrolytic oxygen. When baryta water was substituted for the solution 
of iodide of potassium in D, a precipitate of carbonate of baryta appeared in the 
