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General expressions are derived for the pairwise fluctuations of thermodynamic properties in multicomponent systems, in terms of thermodynamic derivatives. The expressions are valid for an open system close to thermodynamic equilibrium in contact with an energy and mass reservoir. The system is defined by an arbitrary extensive constraint. Fluctuations involving the entropy S, the volume V, and the number of molecules Ni of each component, as well as their conjugate variables, are expressed as second‐order derivatives of the energy U and Legendre‐transformed functions. Fluctuations involving U itself are obtained in the entropy representation of the fundamental equation.

Hydrogen‐atom reaction rates with thin solid propylene films were studied at 77°K. Propylene was deposited on the walls of a quartz resonance cavity of an ESR spectrometer and hydrogen‐atom concentrations were monitored during reaction. The hydrogen atoms were produced in a 2450 Mc/sec microwave discharge external to the cavity and either diffused into or were pumped through the reaction zone.The products of the reaction were found to be propane and 2,3‐dimethylbutane. The ratio of propane to 2,3‐dimethylbutane in the products increased as the average hydrogen‐atom concentration in the reactor increased. The product distribution and the variation of this distribution with hydrogen‐atom concentration may be explained by the following sequence of reactions: CH3–CH=CH2+H→ lim k1CH3–CH–CH3, 2 CH3–CH–CH3→ lim k2CH3–CH2–CH3+CH3–CH=CH2, [Complex chemical formula] CH3–CH–CH3+H→ lim k4CH3–CH2–CH3.The rate constant k1 was found to be 1.8×106 cc/mole·sec at 77°K assuming that the monitored hydrogen‐atom concentra...

Single crystals of potassium chloride were grown from aqueous solutions under carefully controlled conditions of supersaturation, agitation, and impurity lead chloride concentration. The growth rate of the (100) face was determined.It was found that PbCl2 concentrations as low as 10−8 moles PbCl2/mole KCl decreased the rate of growth, and the retardation increased markedly with increasing PbCl2 concentration. The growth process changed from a layer type to a dendritic form over a small supersaturation range. Mass transfer rates of both KCl and PbCl2 from the solution to the crystal face were estimated and conditions delineated where each may be the rate‐controlling step. A mechanism is proposed to account for the formation of crystal clusters on the surface of KCl at slow stirring rates.

Seed KCl crystals were grown from aqueous solution under conditions of constant temperature, supersaturation, and impurity Pb+ + level. Experiments were carried out both in‐and‐outside a gamma‐irradiation field. The dislocation densities and absolute‐growth rates of the (100) faces of the KCl crystals were measured.With solutions containing about 10−7 moles PbCl2/mole KCl, irradiation had no measurable effect on dislocation density. At lower lead concentrations, irradiation reduced the number of dislocations and a dislocation climb process is suggested to explain the results.The effect of irradiation on growth rates of KCl was insignificant when the Pb+ + concentrations were 10−8 and 10−6 moles/mole of KCl. At intermediate concentrations (around 10−7 moles Pb+ +/mole KCl), the effect of irradiation was such as to decrease the growth rate. A possible mechanism is suggested to explain these somewhat anomalous results.