76 
VARIETIES. 
and had acquired a distinctly brown tarnish, not from sulphur, but from a 
process of ozonation, or, in other words, oxidation. Polished lead similarly 
treated was also oxidized. Ozone had always a tendency to bring metals 
and metallic oxides to their highest degree of oxidation. In this respect it 
was the most powerful oxidizer that was known. A tube containing seve- 
ral rings of metallic arsenic had been placed for a short time in a bottle of 
ozone. The metal had entirely disappeared, and had become transformed 
into arsenic acid. Paper wetted with a solution of proto-sulphate of man- 
ganese was introduced into a bottle of freshly prepared ozone, and in the 
course of a short time black spots appeared oyer the surface, proving that 
the manganese had passed to a higher degree of oxidation. 
Nitrogen and sulphur are easily oxidized by it. Schl'nbein succeeded in 
procuring a quantity of nitre (of which a crystallized specimen was shown) 
by the agency of ozone in contact with nitrogen (of air) and potash. Sul- 
phur was also converted to sulphuric acid. Paper stained with sulphuret 
of lead was immediately bleached when exposed to an ozonic atmosphere. 
Some curious experiments of Schonbein's were now shown, in which por- 
traits and inscriptions were seen in white letters on a dark ground, as a 
result of placing stenciled metallic plates on paper which had been stained 
brown by sulphuret of lead. The uncovered spaces had been exposed to 
light and air, or insulated. The result was that in these spots the sulphuret 
of lead had entirely disappeared, having been converted into colorless sul- 
phate of lead by the oxidizing action of ozone. 
The alleged bleaching properties of solar light on colored articles are thus 
probably due to the agency of ozone, — in other words, to a process of oxi- 
dation and alteration of color.* 
Sulphuretted hydrogen, phosphuretted hydrogen, and all foul effluvia, are 
speedily oxidized and destroyed by ozone. It is, therefore, the great puri- 
fier of the air ; and, owing to its continual exhaustion by oxidating pro- 
cesses, it is difficult to discover the presence of ozone in large and populous 
places, or in close and crowded dwellings. In the open air of the country, 
and on the sea, it constantly exists in a proportion which is probably sub- 
ject to great variation, although ruled by laws which are at present unknown. 
Schonbein had contrived an Ozonometer for testing the amount contained in 
air. It is prepared by immersing paper in a solution made of one grain of 
iodide of potassium, ten grains of starch, and 200 grains of water. The 
paper is dried, and when intended for use, is exposed for some time to the 
air. There is no change until it is wetted with water, when, if ozone was 
present in air to which it had been exposed, a blue color will appear, the 
intensity of which varies according to the quantity of ozone present and the 
* This hypothesis should have its correctness tested by the exposure of colors 
known to fade, in hermetically sealed tubes. Oils,it is well known, are bleach- 
ed in close bottles ; but they may contain air, and wherever there is air there is 
ozone, a very small portion of which possessses remarkable powers of bleaching. 
