489 
1910-11.] On some Nuclei of Cloudy Condensation. 
method of experimenting was therefore expanded and attempts were made 
to see if there was anything in nature which would keep these substances 
active. An answer to this question has been found to be extremely difficult, 
as the quantities of matter involved are extremely minute, of the ultra- 
balance order, as has already been found in these experiments. One 
naturally turns to the oxidising gases in the atmosphere to see if any of 
them will make the salt and iodine active with sunshine. In all pure air 
on the sea-shore there is generally some peroxide of hydrogen and ozone, 
and it seemed possible that their presence might bring about the change. 
Experiments were therefore made with. them. 
Peroxide of Hydrogen. 
To test the effect of peroxide of hydrogen some of the ordinary solution 
was put in the flask E, which was introduced between the filter and the 
sunning flask S, so that the peroxide might be carried by the air into the 
sunning flask and there get mixed with the vapours or gases from the salt, 
iodine, or hydrochloric acid. Another method of introducing the peroxide 
was to saturate some cotton-wool with the solution and pass the air through it. 
No satisfactory results were obtained. If a little condensation did appear, 
as it sometimes did, without the peroxide, the peroxide did not ensure its 
always forming. In these tests only weak peroxide was used, as it has been 
shown in Part I. that strong peroxide is active after sunning. The strength 
used, however, was much greater than is likely to be met with in nature. 
Ozone. 
Ozone is another powerful oxidising agent in our atmosphere, but un- 
fortunately our knowledge of it is somewhat vague. Its origin and even 
the tests for it are under constant revision, most of the early tests not 
being trustworthy, as the indications supposed to be due to ozone may be 
produced either by that or by some other gas, leaving the observer in doubt 
as to what is the agent which produces the results. In experimenting 
with ozone another difficulty presents itself. All methods of preparing 
that gas for experimental purposes give us not only ozone but other active 
gases, with properties in some ways similar to those of ozone ; so that when 
experimenting with ozone we are left in doubt as to whether the results 
are produced by the ozone or by the other gases. If we prepare ozone by 
the electrical methods, we get not only ozone but nitrogen compounds ; if we 
use turpentine, we get, along with the ozone, turpentine vapour ; and so on. 
The most common way of preparing this gas is by the electrical methods, 
the point discharge and the Siemens ozone tube. 
