potassium nitrate is observed at 130°. The endotherm at 290°c orresponding to the first crystalline transition of barium perchlorate culminates in the sharp exotherm at 325°caused by the solid state metathesis. All of the potassium nitrate is used up in the reaction and the next break in the curve is a shallow endotherm at 360°c orresponding to the second crystalline transition of the excess barium perchlorate. During the endotherm at 410°, the sample, which now consists of barium nitrate, potassium perchlorate and excess barium perchlorate, melts completely. This endotherm is succeeded immediately by exothermic perchlorate decomposition at 535°. The 410°endothermic fusion and subsequent perchlorate decomposition observed with this sample is similar to that exhibited by potassium perchlorate-barium nitrate mixtures at 465°. This system, however, is inherently more complex since the metathetical reaction occurring in the presence of an excess of one of the reactants results in a ternary system. This in turn may lead to the formation of lower melting eutectics. Nitrate decomposition occurs above 700°. On thermogravimetric analysis the mixture loses an amount of weight equivalent to the decomposition of barium perchlorate to barium chloride at 565°. It undergoes a further loss in weight above 700°due to the decomposition of nitrate ion.

Effects of A1203 particle size and concentration, flow velocity, and electrode arrangement on the codeposition ratio of A1203 onto Ag-A1203 dispersion films were examined. The following points were observed. In the deposition of Ag-A1203 films on a vertical electrode, the codeposition ratio became larger as the concentration of A1203 increased and the flow velocity dropped. At smaller cathodic overvoltages, the silver crystals grew larger and the A1203 particles codeposited selectively on the silver grain boundaries, rather than on the crystal faces. The grain growth of the silver crystals was suppressed by the addition of Al~O3 to the solution. The adsorption states of A120.~ particles on the electrode were more stable as the particle size decreased. This finding agreed with that in which the codeposition ratio of A1~O3 became larger as the particle size became smaller.

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The characteristics of Ag-Al2O3 films electrodeposited from silver thiocyanate solutions containing Al2O3 particles were investigated. The following results were obtained. As the amount of added Al2O3 particles was increased, the amount of Al2O3 codeposition in the Ag electrodeposited film increased, with a subsequent increase in the wear resistance of the electrodeposited film. The Al2O3 particles codeposited in the films suppressed recrystallization of the Ag film. Dislocations in the annealed films moved in accordance with Orowan's theory in the region where the effect of concentration of Al2O3 particles on the yield stress of the film can be disregarded. As more Al2O3 particles codeposited in the films, the tensile stress of the films became lower. This was proposed as due to the compressive stress occurring at the interface between the Ag crystals and the Al2O3 particles. The electrical contact resistance of Ag-Al2O3 electrodeposited film was higher than that of Ag electrodeposited films.

Mechanisms for the codeposition of Al2O3 particles from silver thiocyanate solution have been investigated. The codeposition rate of Al2O3 onto composite coatings was found to increase with slight agitation near the cathode surface and with larger cathodic overvoltages. The actual cathodic current density was smaller, at low overvoltage, for solutions containing Al2O3 than for those without it. However, the opposite was true at high overvoltage. On the basis of the experimental results, it was felt that Al2O3 dispersion particles suppressed the electrodeposition reaction of silver, since the particles were absorbed on the cathode at low overvoltage. Stirring near the electrode surface promoted the reactions.