Not the least important factors affecting the utilization of gaseous fuels are the remarkable effects of small quantities of catalytic substances, the presence of which may initiate or entirely change the nature of a combustion process. A proper understanding of these factors is therefore of great importance in the control of processes which are fundamental to many parts of applied chemistry. Such processes, however, are also intrinsically interesting for the insight they give into the ultimate mechanism of chemical reaction, and as a result of their study in the light of the theory of chain reactions, many empirical facts relating to combustion processes which previously were obscure now acquire a new significance. Of all these reactions the combustion of hydrogen and carbon monoxide stand in a unique position, for these substances more than any others occur as intermediaries in the burning of gaseous fuels; it is therefore of special interest to realize that the presence of traces of hydrogen may have a profound effect on the combustion of carbon monoxide, not only in lowering the temperature of ignition, but also in influencing the rate of propagation of the flame. This becomes of particular importance when it is remembered that carbon monoxide as used industrially nearly always contains traces of hydrogen.
II. Ignition phenomena in mixtures of carbon monoxide and oxygen sensitized by hydrogen