The autoxidation of stannous chloride has recently been investigated by Filson and Walton (l), who studied the effect of hydrochloric acid on the reaction velocity and showed a linear relation between the velocity and the hydrogen-ion concentration. This paper is a continuation of the above work and is a general survey of certain factors influencing the rate of reaction. APPARATUS AND PROCEDURETwenty-five cc. of an acid solution of stannous chloride were placed in a 150-cc. Pyrex flask of the type used by Filson and Walton. The flask was placed in a thermostated shaking apparatus and connected to a waterjacketed burette containing oxygen gas a t the temperature of the thermostat, 25°C. When the system had come to constant temperature, the shaking apparatus was started and readings were taken on the volume of oxygen absorbed. The speed of shaking was selected as about 1000, since Filson and Walton had shown that higher speeds have no effect on the reaction velocity. REAGENTS AND SOLUTIONSSeveral brands of stannous chloride were used and were found to give varying results. Baker's "purified" salt gave results which were only slightly changed by three recrystallizations under nitrogen from hydrochloric acid solution, consequently this preparation was used in the experimental work. Solutions made from stannous chloride which had been dehydrated by treatment with excess acetic anhydride and washed with anhydrous ether (2) gave results which agreed with those obtained from the recrystallized hydrated salt.The solutions, made in 2-liter batches and stored under nitrogen, contained approximately 32 grams of stannous chloride per liter, and were I
The oxidation of solutions of stannous chloride was first studied extensively by Young1 who found that the reaction was somewhat dependent upon the acidity of the solution, highly sensitive to the action of certain catalysts such as copper and iron salts, and further, was inhibited by some of the alkaloids and certain other substances. The reaction was also studied by Miyamoto,2 who determined the effect of acid concentration, the rate of bubbling of the oxygen, and several other factors.It has been shown by many investigators that autoxidations are catalyzed by the presence of certain metallic ions, notably by those of copper, iron, manganese, cobalt, and nickel. This investigation was originally undertaken with the object of finding out whether or not a mixture of these ions exhibit promoter action in the case of autoxidations. Since no cases of promoter action were found, certain physical and chemical conditions affecting the autoxidation of stannous and cuprous chlorides have been studied.Reagents: In most cases no special precautions were taken to further purify the reagents inasmuch as very pure reagents were available. The stock solutions of stannous chloride were made by dissolving a weighed amount of the salt in air-free distilled water containing enough hydrochloric acid to prevent the precipitation of any of the basic chlorides of tin. These solutions were kept under an atmosphere of hydrogen.Apparatus: The apparatus used in these experiments was essentially the same as that used by Walton.3 This apparatus consists of a burette and leveling tube connected to a reaction flask by means of capillary glass tubing. The reaction flask was clamped in a vertical position and by means of an appropriate mechanism, it was rotated back and forth around the vertical axis.The only deviation from the original apparatus was in the shape of the reaction flask (Fig. i). The bottom of a 150 cc. round bottom Pyrex flask was heated in such a way that a narrow band, extending to within an inch of the end of the neck on either side and parallel to the vertical axis, was softened. This softened portion was then pressed in by the edge of an iron spatula so that a fissure about one-half inch deep was formed. A second fissure was made in a plane at right angles to the first. When shaken, the ridge on the inside of the flask breaks the surface of the liquid and in this way drives the liquid into the gaseous phase and drives the gas into the liquid phase.Method of Procedure: The concentration of acid in the stannous chloride solution was determined by titration of a measured sample with standard
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