64 HOW CROPS FEED. 
several times its weight of air or oxygen.* It is entirely 
insoluble in water. It has, when breathed, an irritating 
action on the lungs, and excites coughing like chlorine gas. 
Small animals are shortly destroyed in an atmosphere 
charged with it. It is itself instantly destroyed by a heat 
considerably below that of redness. 
The special character of ozone that is of interest in 
connection with questions of agriculture is its oxidizing 
power. Silver isa metal which totally refuses to combine 
with oxygen under ordinary circumstances, as shown by 
its maintuining its brilliancy without symptom of rust or 
tarnish when exposed to pure air at common or at greatly: 
elevated temperatures. When a slip of moistened silver 
is placed in a vessel the air of which is charged with 
ozone, the metal after no long time becomes coated with a 
black crust, and at the same time the ozone disappears. 
By the application of a gentle heat to the blackened 
silver, ordinary oxygen gas, having the properties already 
mentioned as belonging to this element, escapes, and the 
slip recovers its original silvery color. The black crust is 
in fact an oxide of silver (AgO,) which readily suffers de- 
composition by heat. In a similar manner iron, copper, 
lead, and other metals, are rapidly oxidized. 
A variety of vegetable pigments, such as indigo, litmus, etc., are 
speedily bleached by ozone. This action, also, is simply one of oxidation. 
Gorup-Besanez (Ann. Ch. u. Ph., 110, 86; also, Physiologische Chemie) 
has examined the deportment of a number of organic bodies towards 
ozone. He finds that egg-albumin and casein of milk are rapidly altered 
by it, while flesh fibrin is unaffected. 
Starch, the sugars, the organic acids, and fats, are, when pure, unaf- 
fected by ozone. In presence of (dissolved in) alkalies, however, they 
are oxidized with more or less rapidity. It is remarkable that oxidation 
by ozone takes place only in the presence of water. Dry substances are 
unaffected by it. 
The peculiar deportment towards ozone of certain volatile oils will be 
presently noticed. 
* Babo and Claus (Ann. Ch. u. Ph., 24 Sup., p. 304) prepared a mixture of oxy 
gen and ozone containing nearly 6 per cent of the latter. : 
