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XLIV. On the Action of Jmely-divided Platinum on Gaseous 

 Mixtures, and its Applicatio7i to their Analysis. By Wm. 

 Henry, M.D. F.R.S* 



^JEVERAL years have elapsed since the President of the 

 ^ Royal Society, in the further prosecution of those re- 

 searches on flame which had already led him to the most im- 

 portant practical results, discovered some new and curioxis 

 phaenomena in the combustion of mixed gases, by means of fine 

 wires of platinum introduced into them at a temperature be- 

 low ignition. A wire of this sort being heated much below 

 the point of visible redness, and immersed in a mixture of 

 coal gas and oxygen gas in due propoi'tions, immediately be- 

 came white-hot, and continued to glow until all that was in- 

 flammable in the mixture was consumed. The wire, I'epeatedly 

 taken out of the mixture and suffered to cool below the point 

 of redness, instantly I'ecovered its temperature on being again 

 plunged into the mixed gases. The same phaenomena were 

 produced in mixtures of oxygen with olefiant gas, with car- 

 bonic oxide, with cyanogen, and with hydrogen ; and in the 

 last case there was an evident production of water. When 

 the wire was very fine, and the gases had been mixed in ex- 

 plosive proportions, the heat of the wire became sufficiently 

 intense to cause them to detonate. In mixtures which were 

 non-explosive from the I'edundancy of one or other gas, the 

 combination of their bases went on silently, and the same che- 

 mical compounds were formed as by their rapid combustion. 



Facts analogous to these were announced in the autumn of 

 last year by Professor Doebereiner, of Jena, with this addi- 

 tional and striking circumstance, — that when platinum in a 

 spongy form is introduced into an explosive mixture of oxy- 

 gen and hydrogen, the metal, even though its temperature had 

 not been previously raised, immediately glows, and causes the 

 union of the two gases to take place, sometimes silently, at 

 others with detonation. It is remarkable, however, that pla- 

 tinum in this form, though so active on mixtures of oxygen 

 and hydrogen, produces no effect, at common temperatures, 

 on mixtures of oxygen with those compound gases, which were 

 found by Sir Humphry Davy to be so readily acted upon by 

 the heated wire. Carbonic oxide appears indeed, from the 

 statement of MM. Dulong and Thenard, to be capable of uni- 

 ting with oxygen at the temperature of the atmosphere, by 

 means of the sponge ; but though this is in strictness true, yet 

 the combination, in all llie experiments I have made, has been 

 extreniely slow, and the due diminution of volume has not 



* From the I'hil. Trans, for 1824, Part II. 

 ' been 



