The presence of small concentrations of inhibitors (CCI,, CL, and HCI) in the air passufp into a bed of burning coke is found to increase the CO content o the combustion &ws at the cxpaw of the CO,. With sufficient inhibitor (> 2.0% CCl,) the effect amounts to almost complete suppression of the formation of CO ,The effect is not due to a promotion of the reduction of CO., d s reaction prorpdhg only to a very Bslpll extent under thc conditions of the ex enments. Further expcnments show that inhibitors can prevent L oxidation of 95 o/ of the co at Ioooo in the prcsence of excess oxygen, if the inhibytor (chlorine) is present in the inlet gases in a concentration greater than a sharply defined critical value (c. 0.5 %). This is an extension to a high tan ture region of the well-known action of halogen compounds on =oxidation at lower temperatures. The inhibition of the oxidation of carbon monoxide is found to be most effective when the area of surface of the silica reaction vessel is greatest and also when the CO and CI, arc preheated together; in an empty reaction tube and with the CO preheated separately from the Cl,, no critical CI, concentration IS found and inhibition is poor.The conclusions from the work on the oxidation of CO are applied ?o the earlier experiments on coke combustion in the presence of inhibitors ; it is inferred from the absence of CO, in the combustion gases produced in inhibited coke combustion, that CO, is not formed as a primary product of the interaction between carbon and oxygen, but is always produced by the oxidation of carbp," monoxide. lliz conception is discussed with reference to the of combustion.The four reactions to be considered in the combustion of Many investigations have been made to decide the relative extent to which these reactions contribute to the overall combustion reaction at different temperatures and under Werent conditions.In particular, experimental evidence has been sought to decide whether the final mixture of CO and CO, obtained by the combustion, arises from an initial CO-formmg reaction (I), or from an initial C0,-forming reaction (2), or, if both are evolved simultaneously, the proportions in which they are produced. In any case, the first formed gas subsequently undergoes oxidizing and reducing reactions (3) and (4, to an extent depending on the chemical and physical nature of the surroundings of the primary reaction, such as the presence of excess oxygen and the temperature and reactivity of the carbon surface. Because of the various chemical and physical conditions that inevitably prevail in such combustion investigations (to name, among many, carbon surface temperature and reactivity), the conclusions of different workers have often been conflicting. The problem has been approached in many ways, but, broadly speaking, from two directions. The first approach has been by experiments involving low pressure and low temperature conditions, to eliminate the complications which reactions (3) and (4) introduce in following the initial reaction. Experiments of t...