Dr. Wilson on the Decomposition of Water by Platinum. 177 



assure you that as long as the art of writing has been practised 

 no letter has ever been written with such an ink. Dealing now 

 again in my ozone business, I found out the other day that all 

 manganese salts, be they dissolved or solid, are decomposed 

 by ozone, hydrate of peroxide of manganese being produced 

 and the acid set at liberty. Now to come round again to my 

 ink, 1 must tell you that these lines are written with a solution 

 of sulphate of manganese. The writing being dry, the paper 

 Is sus})encled within a large bottle, the air of which is strongly 

 ozonized by means of phosphorus. After a few minutes the 

 writing becomes visible, and the longer you leave it exposed 

 to the action of ozone the darker it will become. Sulphurous 

 acid gas uniting readily with the peroxide of manganese to 

 form a colourless sulphate, the writing will instantly disappear 

 when placed within air containing some of that acid ; and it 

 is a matter of course that the writing will come out again 

 when again exposed to ozonized air. Now all this is certainly 

 mere playing; but the matter is interesting in a scientific 

 point of view, inasmuch as dry strips of white filtering paper 

 drenched with a weak solution of sulphate of manganese fur- 

 nish us with rather a delicate and specific test for ozone, by 

 means of which we may easily prove the identity of chemical, 

 voltaic and electrical ozone, and establish with facility and 

 certainty the continual presence of ozone in the open air. I 

 have turned brown my test-paper within the electrical brush, 

 the ozonized oxygen obtained from electrolysed water and 

 the atmospheric air ozonized by phosphorus. The quantity 

 of ozone produced by the electrical brush being so very small, 

 it requires of course some time to turn the test-paper brown. 

 As it is rather inconvenient to write with an invisible ink, 

 I will stop here; not however before having asked your kind 

 indulgence for the many blunders and faults which my ozone 

 bottle will no doubt bring to light before long. 



Yours most truly, 



Bale, July 1, 1847. C. F. SCH(ENBEIN. 



XXXII. On the Decomposition of Water by Platinum and the 

 Black Oxide of Iron at a white heat, with some observations 

 on the theory of Mr. Grovels Experiments. By George 

 Wilson, ilf.D.* 



THE remarkable discovery recently made public by Mr. 

 Grove, that water in certain circumstances, when raised 

 to a white heat, is resolved into its constituent gases, has na- 



♦ Communicated by the Chemical Society; having been read March 15, 

 1847. 

 Phil. Mag. S. 3. Vol. 31. No. 207. Sept. 1847. N 



