The effect of pressure and temperature of reactants, of inert gases, of vessel diameter and of surface condition on the induction periods and explosion boundary of 2H$\_{2}$ + O$\_{2}$ mixtures containing nitrogen peroxide have been determined in the temperature range 350-410 degrees C. The principal results may be summarized: (a) Increase of pressure causes the separation of the upper and lower limiting concentration of sensitizer to increase from zero to a maximum value at the inversion pressure. Above this pressure the upper limit decreases and the lower limit increases linearly with increase of pressure. The induction periods of H$\_{2}$-O$\_{2}$-NO$\_{2}$ mixtures of constant NO$\_{2}$ content decrease rapidly with increase of pressure, approaching a small value asymptotically. (b) All foreign gases lengthen the induction periods and eventually quench the ignition of an explosive mixture of H$\_{2}$-O$\_{2}$-NO$\_{2}$ of constant composition. The order of efficiency of the non-reactant gases in lengthening the induction periods is CO$\_{2}$ > N$\_{2}$ > A = He, whereas the order of efficiency in quenching ignition is CO$\_{2}$ > He > N$\_{2}$ > A. (c) The induction period at the upper limit always exceeds the induction period at the lower limit. The reverse is true of the rates of the slow reactions in the vicinity of the limits. (d) At constant total pressure, rise of temperature causes the upper limit (P$\_{U}$) to be raised according to the equation log P$_{U}$ = - E/RT + constant. E is 19,500 cal. at a total pressure of 75 mm. and increases with pressure to 25,600 cal. at 472 mm. (e) At constant pressure the upper limit decreases and the lower limit increases as the reciprocal of the square of the diameter.

A study of sensitized explosions. V. Some new experiments on the hydrogen-oxygen reaction sensitized by nitrogen peroxide

The kinetics of some reactions in the system containing carbon monoxide, oxygen, and nitrogen dioxide have been studied over the temperature range from 658° to 800°K. It has been shown that the reaction is heterogeneous for the lower pressures of nitrogen dioxide and homogeneous for pressures above 10 mm. The homogeneous portion of the reaction appears to include the oxidation of nitric oxide and the oxidation of carbon monoxide by ``oxides'' of nitrogen. A bimolecular reaction involving nitric oxide and oxygen has been studied. Evidence is presented which indicates that the oxidation of nitric oxide involves two consecutive bimolecular reactions instead of the classical termolecular mechanism.

Reactions in the System Containing Nitrogen Dioxide, Carbon Monoxide and Oxygen; NO3 as an Intermediate in the Classical Trimolecular Oxidation of Nitric Oxide

Cyril Norman Hinshelwood was born in London on 19 June 1897, the only child of Norman Macmillan Hinshelwood, a chartered accountant, and Ethel nee Smith. His father was of Scottish origin, and once he remarked jokingly that some of his ancestors must have been well enough known because a street in Glasgow is named after them. His mother came from the west country. Several members of his family had artistic leanings but none appears to have had associations with science. As a small child he was taken by his parents to Canada, his father having some business there, and for a short time he was at a Montreal kindergarten, and later at a national school in Toronto for a few months. His health was not good, however, and at his father’s wish, his mother brought him back to England. His father died soon afterwards in 1904. Many years later, sailing back from Montreal down the St Lawrence River past Rimouski, he recalled with obvious emotion his childhood memory of how the pilot had been put off there. He went to Westminster City School, where there were two good science masters, H. F. Brand and E. B. Fisher, with whom he remained life-long friends. The Headmaster, too, E. H. Stevens, was scientist with wide interests who helped him a great deal. Here he won a Brackenbury Scholarship to Balliol College, Oxford, but was unable to take it up immediately because of the war. From 1916-18 he worked at the Department of Explosives, Queensferry Royal Ordinance Factory, where his remarkable ability was quickly noticed. Before leaving, at a very early age, he became deputy chief chemist of the main laboratory. His work there on the slow decomposition of solid explosives by measuring the gas evolved stimulated his interest in the mechanism of chemical change, which was to be the main theme of nearly all his subsequent scientific research.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsbm.1973.0015

Cyril Norman Hinshelwood, 1897-1967.

This chapter discusses the thermal reaction between hydrogen and oxygen. There are many possible elementary reactions in the hydrogen-oxygen system, but their relative importance changes radically over diverse ranges of experimental variables. As conditions are altered, some reactions become insignificant while others come to the fore. The reaction mechanism is, therefore, circumscribed by the range of experimental conditions to which it applies. The chapter discusses that for the chain-initiation reaction, the dissociation of hydrogen in bimolecular collisions has been considered in the past. On the face of it, this reaction appeared plausible because it gave an explanation for the marked dependence of the rate of water formation on the partial pressure of hydrogen, and it appeared consistent with the observed overall activation energy in excess of 100 kcal. As neither the dissociation of hydrogen or of oxygen nor the gas-phase reaction between them can be admitted as the chain-initiation reaction, attention is focused on the experimentally established presence of H 2 O 2 in the reacting mixture. If H 2 O 2 is both formed and destroyed in a chain reaction, it attains a steady state concentration that is independent of the chain carrier concentration.

The Reaction between Hydrogen and Oxygen

Es wird eine Ubersicht uber die Fortpflanzung von Flammen, die Detonationsgeschwindigkeit in Gasgemischen und die Entwicklung der Theorien der Kettenreaktionen unter Hinweis auf deren Bedeutung fur die chemische Technik gegeben. Ausfuhrlich wird die Bedeutung labiler Reaktionszwischenprodukte fur die Moglichkeiten des Reaktionsablaufs dargelegt. Die nahere Kenntnis des Ablaufs von Kettenreaktionen wird nicht nur die Vervollkommnung bekannter und die Entwicklung neuer technischer Prozesse fordern, sondern das allgemeine Verstandnis chemischer Reaktionsablaufe grundlegend befruchten.

C. N. Hinshelwood

Papers

The influence of nitrogen peroxide on the union of hydrogen and oxygen.—A problem of “trace catalysis.”