On the Properties of Ozone. 321 



1. Ozone has the property of decomposing the protoxyd salts 

 of manganese, throwing down that metal in the shape of the 

 hydrate of peroxyd of manganese and setting at liberty the acids 

 of the said salts. If aqueous solutions of sulphate, nitrate and 

 muriate of manganese he shaken with atmospheric air which has 

 been strongly ozonized in the usual manner, (by means of phos- 

 phorus,) ozone rapidly disappears, the saline solutions become tur- 

 bid, hydrate of peroxyd of manganese is precipitated in the 

 shape of little scales of a brownish color, and sulphuric, nitric 

 or muriatic acid set at liberty. To cause the decomposition 

 described, it is not required to dissolve the salts, the latter being 

 acted upon by ozone even in their solid state. I make use of 

 this remarkable property of ozone to prepare a specific and deli- 

 cate test for that curious substance. Small strips of the whitest 

 filtering paper are drenched with a weak solution of sulphate of 

 protoxyd of manganese, suffered to dry, and kept in stoppered 

 bottles. 



On introducing such paper into ozonized air, it rapidly assumes 

 a brownish tint, growing darker and darker, the longer the test 

 paper is left suspended within the air. If the atmosphere hap- 

 pens to be strongly ozonized, the discoloration makes its appearance 

 after a few seconds suspension. I hardly need mention that the 

 test paper turns brown when exposed to the action of oxygen, 

 which has been obtained by the electrolysis of water, and exhib- 

 its the peculiar electrical smell. The said paper may also be 

 used to prove that ozone is formed by electrical discharges taking 

 place either in oxygen or atmospheric air. By exposing a bit of 

 test paper to the action of the electrical brush, (playing in air 

 or oxygen,) it undergoes the same change of color as it does 

 within air ozonized by phosphorus, or within the oxygen pro- 

 duced by electrolysing water. But as under the first mentioned 

 circumstances, only very small quantities of ozone are generated, 

 11 requires rather a long action of the electrical brush to turn the 

 te st paper brown. 



Electrical discharges continually taking place in our atmos- 

 phere, and ozone being invariably produced by them, it necessa- 

 ry follows that some small portions of that oxydizing agent are 

 Present in atmospheric air. The correctness of that conclusion 

 ls most easily proved by the means of my test paper ; for on being 

 ^posed to the action of free circulating air, it gradually assumes a 

 br <>wn tint, whilst the paper remains perfectly white, when kept 

 ^closed within a bottle filled with atmospheric air. According to 

 l be state of the atmosphere, the test paper is comparatively more 

 0r less rapidly turned brown, but always slowly. I have strips of 

 P a per which have been very perceptibly turned brown, after a 

 Peek's exposure to the open air. 



8 *co HD Series, Vol. IV, No. 12.— Nov., 1847. 41 



