ie 
78 M. C. Lea on the Action of Ozone, &. 
In this last experiment, the atmosphere was ozonized suflicient 
ly to render iodid of potassium and starch paper instantly blue 
In the two previous, this reaction showed itself more gradually. 
In remarking upon the experiments just detailed, I may 
serve in the first place that the ozone was unquestionably alw 
present in such strength as to bring out its marked chem 
effects. This was demonstrated not only by its action on 
characteristie test paper, but also by its chemical action exh 
in experiment (4). i 
Again, the experiments were tried in the most varied w 
The ozone was produced in two different manners, and o 
strength. The surfaces to be tested were also exposed for W 
varied times, from two minutes to forty-five. 
The nature of the light was also varied, experiment havillg 
been made both with daylight and artificial light. The time® 
exposure to light was very various, and in several cases, all@ 
the first results had been noted, the paper or film still wet w™ 
developer, was carried into the light and exposed for some t 
to see if any faint sensibility existed and would manifest is 
by the prolonged action of light. No such result appeared. 4 
experiments included both iodid and bromid of i paet and b¢ 
paper (of which two different sorts were intentionally used) | 
collodion were used as the vehicles for the silver compoun 
The result appears to show pretty clearly that ozone hi 
wer of giving sensibility to insensitive iodid or bromid 
ver formed in the presence of excess of alkaline iodid, wi 
the excess be left present, as in the bromid experiments, of 
removed, as in those made with iodid. Or at least that 
true in respect to ozone produced in the two manners W 
have described. If Mr. kK i 
» 
stricity which he employs, and not to the ozone p' 
