436 Royal Society ;— 



dry oxygen, the ozone was gradually absorbed. The experiment is 

 not yet finished, but already oue-fourth of the gas in a tube of the 

 capacity of 10 cubic centimetres has disappeared. To produce this 

 effect, the discharge from a machine in excellent order has been 

 passed through the tube for twenty-four hours, 



Wlien oxvgen is thus converted into ozone, a diminution of volume 

 takes place.' The greatest contraction occurs with the silent discharge, 

 and amounts to about ^i^ of the volume of the gas. The passage 

 of sparks has less effect than the silent discharge, and will even 

 destroy a part of the contraction obtained by means of the latter. 

 If the apparatus be exposed for a short time to the temperature of 

 250° C, so as to destroy the ozone, it will be found that the gas on 

 cooling has recovered exactly its original volume. This observation 

 proves, unequivocally, that if ozone be oxygen in an allotropic con- 

 dition, its density is greater than that of oxygen. Experiments still 

 in progress indicate that the density of ozone obtained by the elec- 

 trical discharge must, on the above assumption, be represented by 

 even a higher number than that deduced by the authors from their 

 experiments on ozone prepared by electrolysis. 



When mercury is brought into contact with dry oxygen, in which 

 ozone has been formed by the electrical discharge, it loses to a great 

 extent its mobility, and may be made to cover the interior of the 

 tube with a fine reflecting surface resembling that of an ordinary 

 mirror. It is remarkable that this great change in the state of the 

 mercury is not accompanied by any further diminution of the volume 

 of the gas. The apparatus employed by the authors would have 

 enabled them to estimate with certainty a change of volume amount- 

 ing to -prjrou P^^^ ^^ ^^^ whole. On the contrary, on allowing 

 the apparatus to stand, the gas begins slowly to expand ; and in 

 thirty hours, when the ozone reactions have disappeared, the expan- 

 sion amounts to a little more than one half of the contraction which 

 had previously taken place. 



Dry silver, in the state both of leaf and of filings, has the property 

 of entirely destroying ozone, whether prepared by electrolysis or by 

 the electrical machine. If a stream of electrolytic ozone be passed over 

 silver leaf or filings contained in a tube, the metal becomes altered 

 in appearance where the gas comes first into contact with it ; but no 

 appreciable increase of weight takes place, however long the experi- 

 ment may be continued. The volumetric results are similar to those 

 already described in the case of mercury. 



Arsenic also destroys dry ozone, but, as it likewise combines with 

 dry oxygen, its separate action on ozone cannot be observed with 

 precision. 



Most of the other metals examined, such as gold, platina, iron, 

 zinc, tin, &c., are without action on dry ozone. 



Iodine, brought into contact with oxygen contracted by the elec- 

 tric discharge, instantly destroys the ozone reactions, and a yellowish 

 solid is formed : no change of volume accompanies this action. 



Peroxide of manganese and oxide of copper have, it is well known, 

 the property of destroying ozone, apparently without limit. The 



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