164 On Ozone and its Relations to 
the boiling point, ebullition may be continued, care being 
taken not to wet the test paper. The contents of the vessel 
will be in the following condition, as the test paper will 
show; the vapour is absent of ozone, or, in other words, 
the presence of antozone is indicated by becoming dis- 
coloured or deprived of the amount of oxygen it previously 
held in combination; the water on cooling as before would 
indicate the presence of ozone, but they have been but 
mechanically separated, by quickly shaking the contents 
the opposing principles will combine, and testing the 
same when cool a very dissimilar «effect will be apparent. 
from that previously described, little or no ozone being 
present. In condensing, the vapour gives up the antozone 
and neutralises the excess of. ozone in the liquid from 
which it was derived ; in the presence of the atmosphere it 
however, behaves otherwise, ozonizing the oxygen thereof 
in condensing, it yields a large amount of nascent oxygen 
evident to the test-paper described. With iodide of starch, 
another test for ozone, similar indications ensue. 
The fact may be still further verified. Four ounces Pr 
- distilled water, unboiled as before, is to be prepared by 
adding one drachm of the test fluid, the gum of which 
will be precipitated and render the solution of an opa- 
lescent tinge; two similar quantities of this compound 
solution are to be placed in two similar test tubes, to about 
a quarter fill the same, one is to be corked, allowing a 
small vent aperture for expansion, the other, as previous, 
should have a strip of green test paper inserted at its mouth 
and otherwise left free for evaporation; both are now to 
be placed in a sand bath and gently heated; they will 
gradually, but decidedly, be observed to change from white 
to blue, of deeper intensity as they reach a certain tempe- - 
rature, about the boiling point, they may then be stopped. 
The colour is indicative of an excess of ozone in both. 
The test paper shows an absence of ozone in the vapour of 
one, but in the other instance both vapour and liquid are 
confined ; and if each bear opposite properties, by com- 
mingling them, a neutral result must inevitably ensue. 
Such we find to be the case; but in order that the experi-_ 
ment may be satisfactory, the stoppered tube should be 
allowed to cool, or be artificially coole1 by a stream of. 
water, and in that state shaken to condense the vapour in 
the liquid. Comparing this with the other, although not 
devoid of colour, it is little indicative of free oxygen, — 
the quantity lost by evaporation through the vent aperture 
