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A comparative experimental study of flames propagating in mixtures of oxygen with methyl alcohol, formaldehyde or formic acid has been made. The results have been compared with those obtained in a previous work on methane-oxygen flames and show a remarkable similarity. A kinetic interpretation is proposed.Although methane and its partial oxidation products differ markedly in their behaviour when they are submitted to a slow reaction with oxygen in the gas phase, the experimental results presented in this paper show a remarkable analogy between the burning velocities of the flames propagating in the mixtures of any of these compounds with oxygen, provided the amount of diluent is adjusted in such a manner as to render the flame temperatures identical. As it will be discussed in the last section of this paper the observed analogy finds its explanation in the fact that the branching process happens to be the same, even if some differences occur in the mechanism of the chain reaction by which the fuel molecules are transformed into complete oxidation products. EXPERIMENTAL PARTThe determination of the burning velocities and the flame temperatures will not be described here; the reader should refer to a previous paper [l]. The gases (0, and N2) were commercial dry products with less than 0.5% impurities; the liquids CH30H and HCOOH were "pro analysi" chemicals (purity better than 99.8%); HCOH was obtained in a methanol solution (see below) from paraformaldehyde purissimum.Mixtures involving liquid fuels were preheated to a temperature of 125°C for CH30H, and for HCOH solutions in CH,OH, to a temperature of 160°C for HCOOH. It has been verified that at these temperatures no slightest prereaction took place with oxygen after the mixing of the gases and before their arrival at the burner port. Special care was taken in the preparation of the gas mixtures in order to obtain a homogeneous and constant composition. Injection needles were used together with the gas feeding at the entrance of a very long heated tubing; this tubing was connected (*)

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A comparative kinetical study of flames burning in mixtures of nitrousoxide and different hydrocarbons has been made. It has been found that the mean molecular weight of the chain carriers changes with the nature of the fuel. A probable reaction mechanism requests the formation of alkoxy radicals which decompose more or less easily according to their structure. Concerning the apparent activation energy derived from burning velocities at different degrees of dilution with nitrogen, no systematic change with the nature of the fuel has been observed. UNIVERSIT~ DE LOUVAINLaboratoire de Chimie Inorganique Communiqut a la Soci& Chimique de Belgique le 31 octobre 1963.