DR. ANDREWS ON THE CONSTITUTION AND PROPERTIES OF OZONE. 
quantity of free iodine was introduced into D, and a solution of pure iodide of potas- 
sium into E. After passing 4 litres of air through the apparatus, E was found to 
contain 0‘0015 grm, iodine. This is equivalent to one-tenth of a milligramme of 
oxygen, and, from the large excess of iodine in the first solution, must be a greater 
quantity than could have been carried over in any of the subsequent experiments, 
although in some of them larger volumes of gas were passed through the apparatus. 
The free iodine was determined according to the very delicate method first, I be- 
lieve, proposed by Bunsen. A dilute solution of sulphurous acid was prepared, and 
its strength determined, immediately before analysing the liquid in D, by ascertain- 
ing how many measures of it were required to destroy a known weight of free iodine 
in a solution of iodide of potassium. A corresponding experiment was made with 
the solution in D, from which the quantity of free iodine in it was deduced by a very 
simple calculation. 
I. 10’2 litres of electrolytic oxygen containing ozone were passed through the 
apparatus at the rate of about three-quarters of a liti’e per hour. At the first 
weighing, the barometer was 29*85 in. and the thermometer, 5°*9 C. ; at the second 
weighing, the barometer was 29*98 in. and the thermometer, 5°*3. The value of V 
(see preceding note) was 47 cub. cent. The gain in weight of the double apparatus 
D and E was 0*0375 grm., which gives, when corrected for atmospheric changes, for 
the true gain, 
0*0379 grm. 
The free iodine in the solution contained in D, was neutralized by 112*7 measures of 
a dilute solution of sulphurous acid. The other solution of iodide of potassium, 
which had been prepared at the same time as the first, and to which the same amount 
of acid had been added, required 0*8 measure of the same solution of sulphurous acid 
for neutralization. Hence the iodine eliminated by the action of the ozone was 
equivalent to 111*9 measures. Next, 0'5341 grm. pure iodine was added, togethei* 
with 2 grms. of iodide of potassium, to a few drops of water, and when both were 
dissolved, the solution was diluted till it occupied exactly 100 cub. cent. From the 
mean of two experiments which closely agreed with one another, it appeared that 
100 measures of the solution of sulphurous acid neutralized 95'96 cub. cent, of this 
solution, and hence 1 measure of the former corresponded to 0*005 12 grm. iodine. 
From these data it follows, by an easy calculation, that the iodine disengaged by the 
ozone amounted to 0*609 grm., and the equivalent of oxygen to 
0*0386 grm. 
II. 2*72 litres of electrolytic oxygen were passed through the apparatus at the same 
rate as before. At first weighing, barometer 29*60 in., thermometer 5°*8 C. ; at 
second weighing, barometer 29'60in., thermometer 6°*0 C. Gain of weight of D 
and E 0*0107 grm., corrected, 
0 0107 grm. 
The-free iodine in D, after deducting the iodine due to the small quantity of iodate 
