Insensitive Iodid and Bromid of Silver. 17 
posed to a highly ozonized atmosphere for three minutes. It 
was then exposed to a large gas light for fifty seconds. On the 
application of an iron developer no darkening was observable. 
(10.) In order to afford a term of comparison, a film of ordi- 
nary collodion was sensitized in the negative bath in the usual 
manner, and was exposed to the same light for twenty seconds. 
On ~ application of the same developer it was strongly dark- 
ene 
(11.) The same collodion as ‘in (9) was exposed to the same 
ozonized atmosphere for 45 minutes. It was next exposed to 
the same gas light as (8) and (9) for thirty seconds. The appli- 
‘cation of the developer produced no darkening. 
(12.) Same as (10), but exposed to light for one and a half 
minutes. Result as before. 
13.) Same, but exposed tolight for three minutes. Result as 
before. In no case was the slightest reducing effect produced. 
B. OZoNE BY CHAMELEON MINERAL, 
Action on Bromid of Silver. 
The bromid of silver was used in the same form as before, 
viz: in collodion containing a small excess of bromid of am- 
monium. I should have mentioned before that the insensibility 
to light of this argento-ozonized collodion was first carefully 
and proved. Ozone was generated in a closed box 
the action of undiluted sulphuric acid on chameleon mineral ; 
the vessel containing which was set aside for a short time to let 
the i isa vapors pass off. It was then set in the box, and the 
Condition of the atmosphere was examined from time to time 
by appropriate test paper. : : 
14.) Before commencing with the ozone trials, a piece of glass 
was collodionized with ordinary collodion and sensitized in the 
negative bath. It was then exposed to a weak diffuse “ries 
(15.) The eollodion containing insensitive bromid was exposed 
to a weakly ozonized atmosphere for ten minutes. It was then 
to the S 
mentioned in (14), and for the same time. An iron developer 
was then applied, but not the slightest indication of sensitive- 
ness bl 
