Insensitive Iodid and Bromid of Silver. 75 
source of the ozone was not the same as that used by M. Kaiser, 
my results cannot be considered as strictly controlling his, but 
the action of ozone from the two sources is so similar that we 
should naturally expect similar results in the two cases. 
A. OZONE BY PHOSPHORUS, 
The ozone was generated in a large bell glass, and the experi- 
ments were not commenced till paper impregnated with starch 
and alkaline iodid exhibited an immediate and strong ozone re- 
action. 
I. Action on Jodid of Silver. 
Paper was plunged into an ordinary negative bath, and dried. 
Strips were immersed in solution of iodid of potassium, and 
without leaving them in too long, were next thrown into clean 
water and washed. 
(1.) A piece of this paper, thus imbued with washed insensi- 
tive iodid of silver, was placed in the ozone a paratus for two 
minutes. It was then exposed to diffuse dayJight for six sec- 
onds. The application of an iron developer produced no dar 
ening whatever. A longer exposure to light was also without 
effect. The paper was just as insensitive as before being exposed 
to the ozone. 
(2.) The effects of a longer exposure to the ozone were next 
tried. The paper, prepared as before, was exposed for half an 
hour to the action of the ozone, and exposed to a moderate dif- 
fuse daylight for twenty seconds. The iron developer produced 
no effect whatev 
(8.) Same as 
Result as before. aut 
4.) The paper was prepared as before, but, after immersion in 
the solution of iodid of potassium, the washing in water was 
Omitted, and the strip was placed in the ozone apparatus just as 
It left the solution of iodid. The paper immediately changed 
to a deep chocolate brown, while still in the ozone apparatus. 
This effect was at once attributed to the action of the ozone on 
the free alkaline iodid, but to place the matter beyond doubt, 
he paper was thrown into a solution of hyposulphite of soda, 
Which instantly bleached it.. —- 
It seems hardly likely that this reaction, so well known, could 
have been mistaken for an indication. of sensitiveness to light. 
Perhaps, if the exposure to ozone had been conducted in dif- 
‘use daylight instead of in a dark room, a careless experimenter 
might have been misled, by the similarity of the chocolate-brown 
Color produced to that so often occurring in photography, intoa 
misap »rehension of the agency at work, and might ave supposed 
that she ozone had rendered the insensitive iodid of silver sensi- 
r. 
2), but exposed io light for thirty seconds, 
