1884] The Exhalation of Ozone by Flowering Plants. 339 
men who kindly cooperated with him. In these investigations 
three kinds of tests were employed, to wit: Schoenbein paper, 
paper impregnated with tincture of guaiacum, and paper impreg- 
nated with solution of thallous hydrate. The doctor gives the 
methods of preparing these different papers. The Schoenbein is 
made according to the following formula: Potassium iodide 5 
parts, starch 50 parts and water 1000 parts. The starch and 
iodide are rubbed with a small amount of water until a milky 
homogeneous fluid is produced, and then the rest of the water is 
added and the whole boiled for some time with constant Stirring. 
The freshly prepared paste is spread on strips of filter paper, 
which are afterwards dried in a close room. The filter paper used 
is the best Swedish (Munktells). The guaiacum is made from a 
ully prepared tincture containing 8 per cent of resin and 
9 per cent of alcohol. When exposed to artificially prepared 
Ozone this paper turns greenish-blue and finally a bright blue, 
while the Schoenbein turns quite blue. The papers employed in 
the present researches were very kindly prepared for me by Pro- 
fessor Henry Leffman after the above formulz, and they gave 
excellent reactions both in the hands of the professor and in my 
om hands, when exposed to ozone artificially prepared. The 
iodized starch, or Schoenbein, being universally acknowledged to 
be the Most sensitive, as well as giving the most reliable results | 
me reactions obtained by this test were considered of paramount 
portance and value. There are, however, sometimes other 
| bodies present in the atmosphere which have the power of de- 
ic iodide of potassium, and hence give a blue reaction 
. Well as ozone, to wit, peroxide of hydrogen, the oxides of 
i Mio and ammonia. The latter substance can be detected by 
; ee à piece of red litmus near to the test papers, the effect 
. nalo aa the paper blue. The presence of the nitrous oxides 
mm: Teadily demonstrated. How to avoid mistaking the 
: aa of hydrogen for ozone may prove difficult, 
Wat substances appear to have many properties in com- 
Whether "eee. it has been a disputed question among chemists 
W Possible to distinguish between them by any known 
: Claims to be abe > R. Leeds (Chem. News for April 9, 1880) 
; "i . “The epee each by its own properties. He 
ost striking property of ozone is its smell. 
So far as long continued familiarity with it enables me 
