﻿114 M. H. St.-Claire Deville on the Temperature of Flames, 



I have said that if the flame of hydrogen becomes luminous 

 under a high pressure, it arises from the temperature of the flame 

 increasing in proportion as the pressure at which the combus- 

 tion takes place itself increases. Let us now see what are the 

 consequences of this fact, supposing it to be well established. 



M. Debray and I have proved that the temperature of combi- 

 nation of hydrogen and oxygen, under the ordinary pressure, 

 is 2500°. We determined this fixed point by throwing into water 

 a kilogramme of melted platinum raised to the highest tempera- 

 ture which could be produced in a lime-furnace, taking into 

 account the increase in the temperature of the water, the specific 

 heat of platinum and the law of its increase given by M. Pouil- 

 let, along with its latent heat as determined by M. Person. We 

 should have liked to control so important a result by a great 

 number of tests, and to fix it, as far as the data of calculation 

 permitted, in an incontestable manner. For that purpose it 

 would have been necessary to use large masses of platinum, and 

 to protect ourselves against very serious accidents, terrible ex- 

 plosions, of which we narrowly escaped being the victims. We 

 were closely occupied with the solution of this question when 

 Professor Bunsen published his beautiful memoir on the tempe- 

 rature of combustion*. The excellence of the method invented 

 by the great Heidelberg physicist made it unnecessary for us to 

 recur to a tedious and dangerous method, the more so as the 

 numbers obtained by Professor Bunsen are in the most com- 

 plete agreement with our own. Professor Bunsen gives 2800° 

 as the temperature of combination of the two gases purified 

 and introduced in a state of absolute dryness into his valve- 

 eudiometer. Allowing for the moisture of the gases used in our 

 experiments, and for the nitrogen brought into the gasholder by 

 the water which displaced the gas, a number is obtained very 

 near 2800°, which I shall adopt for the future as the true tem- 

 perature corresponding to this phenomenon. 



Taking the number 2500°, I obtained the fraction 0*44 f to 

 represent the portion of the gases which really combine at the 



dissociation took place with the production of oxygen and of a yellow 

 pulverulent and light carbon, to which, according to all appearance, is due 

 the blue tint of the flame. M. Cailletet has observed that, in withdrawing 

 and suddenly cooling the gases from the tuyere of a blast-furnace by means 

 of my hot and cold tubes, these gases, produced by a carbon absolutely 

 destitute of volatile matters, were rendered almost opaque by a sort of 

 -thick brownish fog, which after the lapse of some time was resolved into a 

 blackish-yellow deposit of extremely finely divided carbon. 



* Pogg. Ann. vol. cxxxi. p. 161 ; Phil. Mag. S.4. vol. xxxiv. p. 489. 



t Compare Lemons de la Societe Chimique {de la Dissociation), p, 290 

 (Paris, Hachette, 1866). 



