120 
DE. ANDEEWS AXD PEOFESSOE TAIT OX THE 
related to one another, that the expansion due to the one is exactly equal to the con- 
traction arising from the other. Such a supposition can, however, not be considered 
probable. 
§4- 
In order to subject this remarkable property of ozone to a further examination, two 
additional series of experiments were undertaken, to a description of which we now 
proceed. 
In the first series, a primary and an auxiliary vessel with large reservoir’s were filled 
with pure and dry oxygen, small capsules hermetically sealed, and containing portions 
of the same solution of iodide of potassium, having been previously placed in each. The 
silent discharge was passed through the primary vessel so as to produce a considerable 
contraction, amounting in difierent experiments to from 40 millims. to 80 millims. The 
levels of the acid in the siphon tubes of both vessels ha\ing been carefully read while 
the vessels were in the calorimeter, the ends were sealed, and the vessels shaken so as to 
break the capsules in both. In the primary vessel, the iodide of potassium solution 
became instantly coloured dark brown from the iodine set free, while that in the auxi- 
liary vessel did not change. On replacing the vessels in the calorimeter, and opening 
the ends of the siphon tubes, the change in the levels indicated a considerable expan- 
sion in both. In the auxiliary vessel, this expansion was due to the tension of the 
vapour of the solution of iodide of potassium alone ; in the primary vessel, the expan- 
sion ought to have been less than this, on account of the absorption of ozone, if the 
volume of that body were capable of measurement. 
In the following Table, which contains the results of five very careful experiments 
made in this way, the first column gives the amount of contraction produced by the 
silent discharge in the primary vessel, previous to the breaking of the capsules; the 
second, the temperature ; the third and fourth, the respective expansions in the primary 
and auxiliary vessels ; and the fifth, the differences of the numbers in the third and 
fourth columns : — 
I. 
mm. 
81-5 
li’OC. 
mm. 
68’5 
mm. 
70’0 
mm. 
— I’O 
II. 
62-2 
13’5 C. 
79’5 
80-0 
-0’6 
III. 
72’2 
8’7C. 
50’7 
52’0 
-I’3 
IV. 
63’5 
12-2 C. 
71-5 
73’() 
-I’O 
V. 
45-5 
16’2 C. 
87-0 
89’2 
9-9 
— — ^ ^ 
The capacity of the vessels 
employed in 
these experiments 
was 
about 30 cub. 
the primary and its auxiliary were found, in each experiment, by careful comparati^e 
observations, to work accurately together. The solution of iodide of potassium was 
purposely employed of different strengths in the several experiments. In I. it contained 
4 ^th part of iodide of potassium ; in II. 2 -^th ; in III. ^rd ; and in IV. and V. |^th. 
In the two last the solution was slightly acidulated with hydrochloric acid, in the othei-s 
it was neutral. The capsules contained each about O’ 7 grin, of these solutions. 
