416 Dr. Henry on the Action of [June, 



Article III, 



On the Action of finely divided Platinum on Gaseous Mixturesy 

 and its Application to their Analysis. By William Henry, 

 MD. FRS * 



Skveral years have elapsed since the President of the Royal 

 Society, in the further prosecution of those Researches on 

 Flame, which had already led him to the most important 

 practical results, discovered some new and curious phsenomena 

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

 platinum introduced into them at a temperature below 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 proportions, immediately became white hot, and continued 

 to glow until all that was inflammable in the mixture was con- 

 sumed- The wire, repeatedly taken out of the mixture and 

 suffered to cool below the point of redness, instantly recovered 

 its temperature on being again plunged into the mixed gases. 

 The same phaenomena were produced in mixtures of oxygen with 

 defiant gas, with carbonic 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 explosive proportions, the heat of the wire became 

 sufficiently intense to cause them to detonate. In mixtures, 

 which were non-explosive from the rpdundancy of one or other 

 gas, the combination of their bases went on silently, and the 

 same chemical compounds were formed as by their rapid com- 

 bustion.t 



Facts analogous to these were announced, in the autumn of 

 last year, by Prof. Dobereiner of Jena, with this additional and 

 striking circumstance, that when platinum in a spongy form is 

 introduced into an explosive mixture of oxygen 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 detona- 

 tion. It is remarkable, however, that platinum 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 uniting with oxygen at the tempera- 



• From the Philosophical Transactions, for 1824, Part II. 

 -)• Philosophical Transactions, 1817, p. 77. 

 j DiibereineT in Ann. de Chim. et de Phys. xxiv — xcvi, 

 § Ditto xxiii. 4i2. 



