I 49 
1880.] History of Ozone. 
He brought forth a variety of hypotheses, thus introducing 
great uncertainty into a confessedly difficult subject, and 
necessitating the labours of chemists during nearly a quarter 
of a century for their complete overthrow. 
His earliest hypothesis was that ozone is a compound 
consisting of hydrogen and oxygen. This, in 1844, he 
abandoned in favour of the theory that ozone itself is 
elementary, and along with hydrogen enters into the com- 
position of nitrogen, which is a compound substance. The 
following year he reverted to his original hypothesis, and, 
while maintaining strenuously that ozone is not peroxide of 
hydrogen, he nevertheless upheld the view that it is com- 
posed in certain unknown proportions of hydrogen and 
oxygen. 
The second hypothesis was overthrown by the experiments 
of Marignac and De la Rive, who showed that ozone could 
not be derived from the decomposition of nitrogen, inasmuch 
as they obtained it by passing eledtric sparks through per- 
fedtly pure and dry oxygen. They proved the resultant body 
to be ozone, by causing it to readt on moist silver and 
potassium iodide with the formation of argentic peroxide 
and iodate of potassium. They explained these readtions 
by supposing that under the influence of the eledtric dis- 
charge the oxygen had acquired an eledtrified condition, 
with exalted chemical properties : in other words, that ozone 
is oxygen, and oxygen only, but oxygen in an eledtrified 
state. Plausible as was this explanation, there was nothing 
in the experiments — water having been present in the re- 
adtion upon silver and potassium iodide — to confute the 
different interpretation brought forward by Schonbein, that 
ozone was oxygen to which in some way was added the 
elements of water. Nor was this point settled by a more 
elaborate experiment of the same nature, instituted by 
Fremy and Becquerel in 1853, who demonstrated that when 
a certain volume of oxygen is confined over an aqueous 
solution of potassium iodide, moist silver, or mercury, all 
of the oxygen undergoes absorption by the reagent under 
the influence of a sufficiently prolonged series of eledtric 
sparks. 
The first to abandon the theory that hydrogen is a 
constituent of ozone was Schonbein himself (1849). He 
employed air, ozonised as strongly as possible by moist 
phosphorus, and afterwards dried by passage through a 
sulphuric acid drying tube. That water was employed in 
the generation of the ozone was not from Schonbem’s point 
of view an essential element in the problem ; it was whether 
