The formation of OH in the shock wave induced combustion of H2 and O2 has been measured by oscillographically recording the absorption of ultraviolet OH line radiation. The main features of the reaction course are: (1) an induction period whose length, ti, varies inversely with [O2], (2) an increase in the product [O2] ti as ti becomes short compared to the vibrational relaxation time of O2, and (3) at the end of the induction period, a sigmoid rise of [OH] to a maximum, followed by a slow decrease. ti has been studied over the ranges: 1100°≤T≤2600°K, 1.3×10—5≤[O2]≤8.0×10—4 mole/1, 0.25≤[H2]/[O2]≤5., 0.004≤[O2]/[Ar]≤0.20, and 5≤ti≤500 μsec. Agreement between incident and reflected shock experiments has been demonstrated. According to the branching chain mechanism known from explosion limit studies, ti is governed by the rate of H+O2→ lim k1OH+O according to: 2 k1[O2]ti=2.303 n, where n is the number of decades by which [OH] increases between initiation and the end of the induction period. The values of [O2]ti, which is nearly proportional to 1/k1, are summarized by: log10([O2]ti) (mole 1—1 sec)= —10.647+(3966±625)/T. The value k1=1.4×109 deduced at 1650°K from this work is combined with data near 800°K to give: k1=3×1011 exp(—17.5±3. kcal/RT) (mole/1)—1 sec.—1. The relation of these results to detonation experiments is discussed.

The shuck pyrolysis of N2Os in the presence of excess argon has been studied, thus providing information about the properties and reactions of the nitrate free radical, NO3. The important reactions are: N/O5 N02 + NO3 (A and B), N02 + NO3 -» NO + 02 + N02 (e), NO + NO3 -* 2N02 (f), NO3 + N03 -* 2N02 + 02 (g). In the concentration and temperature range studied ([argon] ~0.0076 mole/1., 450-550°K.), the dissociation reaction is a unimolecular reaction close to its second order low pressure limit, -d[N205]/df = A'[A] [N205], with A' = 1013-7 exp(-16,500 ± 700/i?r)(mole/l.)-1 sec.-1.The equilibrium constant of the dissociation reaction is given by Ac = 104-97 exp( -20,100 ± 1100/l?r)(mole/l.). The rate constants of e and g are given (550-1100°K.) by e = 2.3 X 10s exp( -4400 ± 700/l?r)(mole/l.)-1 sec.-1 and g = 2.6 X 109 exp(-7700 ± 1000/1? T)(mole/l.)-1 sec.-1. On the basis of this and other data, the following thermodynamic quantities are calculated: N2Os = NOa + N03, AH\0ok. = 21,600 cal./mole, ASWr. = 33.6 e.u., Aff°i,,0i (NOa) = 17,100 (±1000) cal./mole, S°m (NO3) = 60 ± 2 e.u. The kinetics of various reactions involving NO3 are reviewed and recommended rate constants and activation energies at 300°K. computed. In general, the present investigation, where N03 was a major constituent whose concentration was directly measured, confirms the results of previous investigations in which NO3 was present at low, undetermined concentrations as a reactive intermediate. (1) Research carried out under contract Nonr-220(01) between the

Sets of pressures and their corresponding specific volumes and internal energies are derived from measurements on steadily propagating, planar shock waves propelled by explosively driven metal assemblies into a 1:1 atomic mixture of the elements nitrogen and oxygen in each of two liquid initial states. One of these is the equimolar solution of O2 and N2, at T≂85 K, v0≂1.06 cm3/g; the other is the pure explosive compound NO, at T≂122 K, v0≂0.79 cm3/g. Results for this system are calculated with effective spherical potentials and presented graphically for comparison with the measurements. Single- and reflected-shock states are reported, as are incidental new results on pure liquid N2 at 85 K. The method of measurement is described, with reference to its previous applications to liquid O2 and Ar. First-shock pressures from both initial forms lie between 10 and 30 GPa, and the Hugoniots intersect at a common state, near 21 GPa, where a single reflected-shock Hugoniot is centered. Concordant measured state variables at this intersection provide novel confirmation of the expectation, inherently incorporated into theory, that unique equilibrium states are reached. Accounting for densities of these states by theory indicates a significant amount of oxidized nitrogen, in reversible equilibrium with major, but not exclusive, N2 and O2 components. This is treated as residual NO only, although the uncertainty in the potentials for other oxides does not assure their absence.

The rate of the dissociation reaction, kD M+k;:~ M+I+I, kR has been measured by the shock tube method for argon, helium, nitrogen, oxygen, and carbon dioxide as inert gases, M, in the temperature range 1000o-1600 o K. The shock wave results by themselves and the comparison of the shock wave measurements with the room temperature measurements of kR by flash photolysis both show that kR has a negative temperature coefficient. The absolute value of this negative temperature coefficient derived from the shock wave measurements is greater than the value derived from comparison of the average high temperature result with the room temperature result for any particular gas. This may be due to experimental error in the determination of dkR/dT at the high temperatures, but it is believed that the values of kR determined in the middle of the temperature range studied are reliable.The experimental evidence indicates that, for the measurements with CO2, the rate of vibrational equilibration is so fast that the observations made here pertain entirely to vibrationally equilibrated C02. Evidence from other experiments indicates that the rate of vibrational relaxation in oxygen is such that most of the dissociation reaction occurs in relaxed 02, but that nitrogen remains vibrationally unexcited under the conditions of the dissociation reactions studied here.The ratio, kR, 12/kR,A, of the efficiencies of iodine and argon as third bodies is not greater than 30 at 1300 0 K whereas it is 250-600 at room temperature. The hypothesis is proposed that in general the ratio kR, .. ,/kR.A for complex gases will decrease with increasing temperature.

Spinning detonation waves in acetylene-oxygen mixtures highly diluted with argon have been studied in circular tubes by a variety of simple photographic, electrical, and mechanical (soot inscription) techniques. The combined results of these experiments permit the deduction of a fairly detailed description of the system of shock waves, reaction zones, and contact zones which exists at the front of the spinning detonation. The outstanding feature of the observed structure is that about half of the gas near the tube wall is burned in a wave which propagates in a nearly circumferential direction through shocked, unburned gas behind the nonplanar primary shock front. The relation of this structure to that of White's ``laminar detonations'' in rectangular nozzles and to spinning detonation wave structures recently proposed by certain Russian workers is discussed.