There are frequent references in the literature to the decomposition of hypochlorite solutions on keeping or by heating, and to their decomposition by light.The first mention of their decomposition by metallic oxides is by Balard(l) who observed that in the presence of silver oxide hypochlorites are decom posed with evolution of oxygen. Gay Lussac (2) found a similar decom position in the presence of powdered pyrolusite, and this was confirmed by Mitscherlich (3). Fleitmann (4) suggested warming hypochlorite solutions with the oxides of cobalt, nickel, copper or iron as a means of preparing oxygen, and Bidet (5) described a method of obtaining a continuous stream of oxygen by the action of cobalt oxide on bleaching powder. Bottger (6) has examined the action of barium peroxide.Several references occur to the rapidity of decomposition of bleach liquors containing iron (7) or copper (8), or in contact with metals (9) and the relative effects of various metallic oxides have also been examined (10).No quantitative examination of the decompositon by metallic peroxides appears to have been made. During an investigation (11) of the precipitation of the higher oxide of cobalt by means of alkali and hypochlorite, interest was aroused in the decomposition of the excess of hypochlorite by the precipitated oxide and this reaction has now been investigated.Materials.-The sodium hypochlorite solution was made by bubbling washed chlorine, generated from potassium permanganate and hydrochloric acid, into aqueous sodium hydroxide below 15°. A little free alkali was left to retard on May 10, 2018 http://rspa.royalsocietypublishing.org/ Downloaded from

THE solubility of carbon dioxide in water in the presence of starch was determined by Pindlay and Williams (T., 1913, 103, 636) at pressures lower than atmospheric, and by Findlay and Creighton (T., 1910, 97, 536) a t pressures above that of the atmosphere. From these determinations it appeared that the solubility increases slightly and continuously as the pressure is increased. As this behaviour is different from that found in the case of other colloids it seemed advisable t o re-determine this solubility.The apparatus employed was the same as that previously used, but it has been found possible t o improve its working and manipulation so as t o increase the accuracy of the measurements. We believe the accuracy of the present determinations may be taken as not much less than 0.1 per cent. I n the previous determinations thO initial and final volume of the gas in the burette was read a t different pressures, and the dead space correction which had to be introduced was rather large. I n the present series of determinations the dead-space correction was eliminated by reducing the pressure on the gas in the burette and connecting capillary to atmospheric pressure after the absorption of the gas. The volume of gas was, therefore, always read a t the same pressure. This reading can be done more accurately than the reading of pressure, and although readings of the pressure must also be made, errors in such readings have comparatively little influence on the final result. By working in this way, also, the calculation becomes simplified, the solubility being given by the expression :

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