470 reports on the state op science. 



Introduction. 



The era in the scientific investigation of gaseous combustion with which 

 this Eeport is specially concerned was inaugurated some thirty years 

 ago by the pioneering researches of the French savants Mallard and 

 Le Chatelier, and M. Berthelot, on the initial stages of ' inflammation ' 

 and the setting up of ' detonation ' in explosive mixtures, and by the 

 equally fruitful discoveries of H. B. Dixon and H. B. Baker concerning 

 the part played by steam in combustion. Previous knowledge of the 

 chemistry of fire had been mainly derived from the researches of Davy 

 and his contemporaries (1815 to 1825), and those carried out or inspired 

 by Bunsen some fifty years later. Davy's work, primarily undertaken 

 in order to elucidate the causes of explosions in coal-mines, had disclosed 

 and brought within range of experimental inquiry the broad facts con- 

 nected with the ignition of explosive mixtures, the influence of narrow 

 passages and of cold surfaces in extinguishing flames, the relative ' com- 

 bustibilities ' and ' explosion limits ' of inflammable gases, and the 

 effects of rarefaction and dilution upon gaseous combustion. Finally, 

 his notable discovery of the flameless combustion of hydrogen and of 

 coal-gas in contact with a glowing spiral of platinum, followed by the 

 more systematic investigations of Dulong and Th6nard, had drawn atten- 

 tion to the ' intensifying ' influence of hot surfaces upon combustion, the 

 importance of which has perhaps never been fully appreciated. 



But the work of Davy, standing as it does between the ages of 

 Lavoisier and Clausius, and singularly fruitful as it was in its immediate 

 practical results, gave rise to no great theoretical developments. Soon 

 after his death the path of progress became choked with error; there 

 arose the dogma of the selective combustion of hydrogen in hydrocarbon 

 flames, which, although inconsistent with Dalton's experiments on the 

 partial combustion of ethylene and methane, continued to dominate 

 chemical science for more than half a century. There is no evidence that 

 Davy himself ever countenanced this doctrine, but it possibly may have 

 been suggested to his immediate successors by his mistaken views con- 

 cerning the much higher combustibility of hydrogen as compared with 

 hydrocarbons — a notion which is still widely prevalent. 



Bunsen 's researches upon gaseous combustion, whilst they did in- 

 calculable service to chemistry and metallurgy in introducing exact 

 methods of gas analysis and in elucidating the reducing action of carbon 

 monoxide in the blast furnace, unfortunately gave rise to certain 

 misconceptions, due to unsuspected errors in the experimental methods 

 employed. His experiments on the division of oxygen between carbon 

 monoxide and hydrogen, which were originally undertaken to test the 

 law of mass action, are now recognised to have been vitiated by the fact 

 that he worked with undried gases in a ' wet ' eudiometer. From his 

 results, however, he concluded that the condition of equilibrium in such 

 a case is determined by an assumed tendency to form certain ' hydrates 

 of carbon dioxide,' and undergoes discontinuous alteration on gradual 

 change in the relative proportions of the combustible gases originally 

 present. But whilst this conclusion was afterwards disproved by the 

 independent researches of H. B. Dixon and Horstmann, the underlying 



