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Ozone is formed by passing an electric current through 
air or oxygen gas. Schonbein discovered that it was also 
generated, during the slow oxidation of phosphorus, in 
moist air. Ozone is a powerful bleaching and oxidising 
agent, possessing the property of purifying decomposing 
animal and vegetable substances. It oxidises many of the 
metals, is insoluble in water, and in solutions of acids and 
alkalies. If breathed in a concentrated state, it has a 
powerful effect on the animal system. To test the presence 
of ozone in the atmosphere, Schonbein proposed the 
employment of slips of paper impregnated with iodide of 
potassium and starch. These are exposed to the atmosphere 
with certain precautions ; if ozone is present, these papers 
become coloured, and the depth of colour is supposed to 
indicate the amount of ozone. Schonbein at first supposed 
that ozone was a new electro negative element, analogous 
to chlorine and bromine ; afterwards he suspected it to be a 
constituent of nitrogen. His investigations were continued 
for many years, and, from certain experiments, he concluded 
that oxygen could exist in three distinct states. When 
electro negative it was ozone, when positive it was antozone, 
and when these two states were combined it became passive, 
or neutral oxygen. 
There are some scientific men who do not think the 
existence of antozone is satisfactorily proved. The elaborate 
researches of Dr. Andrews and Professor Tait have added 
largely to our knowledge of the nature and properties of 
ozone. These gentlemen discovered that when oxygen gas 
has been ozonised by a discharge of the electric current 
the volume of gas was diminished — for example, 100 
volumes of oxygen become reduced to about 92 volumes. 
If changed back again by the agency of heat, or otherwise, 
it becomes 100 volumes again. Sordt discovered that the 
oils of turpentine and cinnamon, being brought into contact 
with ozonised oxygen, the whole of the ozone was absorbed. 
He concluded that ozone was 1£ times the density of 
