> 
1885.] The Exhalation of Ozone by Odorous Plants. 859 
not blooming, were first selected and placed within the glass case. 
The test papers were moistened and suspended on the branches 
of the plants. After adjusting the removable part of our case, 
the latter was found to be pretty well filled though not over- 
stocked with plants. For the purpose of detecting any alkaline 
substance whose presence, it is said, will change the Schoenbein 
and guaiacum pdpers in a manner indistinguishable from that 
produced by ozone, we suspended with the test papers a piece of 
red litmus, with the results indicated in the following tables. The 
air on the exterior of the case was simultaneously tested for 
ozone. In view of the fact that these tests are in an unsatis- 
factory state, the necessity for taking precautions against inter- 
fering conditions must be obvious to the mind of the scientfic 
reader. ; 
The following table will serve to show the results obtained 
from the specimens above named for seven consecutive days in 
the month of June, 1884: 
: ; s Schoenbein : State of | Litmus 
No. experiment.| Schoenbein, Guaiacum. $ open wir. Time. | ovat hee. | (red). 
“iene, SES ...| negative | negative | negative | Shours| clear | negative 
Mach 266 ‘ ‘ec g «s “ s 
ee i, slight marked | marked jrr “ -a blue 
NO vD aa negative slight negative | 9“ n negative 
Ee ae very slight | marke o 7 G vd 
haa a eee roe x " negative |Io “ st a 
Na WIS ges slight marked slight | 8 « be blue 
These results are in exact accord with those previously re- 
corded (supra) by one of us. It should be remarked that whilst 
two “slight” reactions occurred with the Schoenbein paper, they 
were probably due to the presence of some alkaline substance, 
since on the same days the red litmus was changed to a 
“marked” blue. Thus, after repeated experiments, it would 
appear certain that it cannot be claimed for non-odorous foliage 
plants that they are ozone-generating. Though the guaiacum 
Paper gave “ slight” reactions in three experiments which yielded 
no results with the litmus paper, it should be here noted that 
Owing to the fact that this paper (guaiacum) is materially affected 
by various atmospheric conditions, we did not much rely upon 
the results obtained from its employ. On the other hand, if 
_ Proper precautionary measures be taken, the Schoenbein is, 
doubtless, of all the tests for ozone the most reliable. 
