(iii). 2HClO = 2HCl + O_{2} (iv). CaCO_{3} + 2HCl = CaCl_{2} + CO_{2} + H_{2}O. Phelps, during the hearing of this case, suggested that hypochlorites were directly toxic to micro-organisms but this view was not supported by any definite evidence and the nascent oxygen hypothesis met with almost universal acceptance. Investigations made by the author in 1915, 1916 and 1917 have produced data which cannot be adequately explained by the nascent oxygen hypothesis.[3] The disinfecting action of bleach can be most conveniently considered by regarding it as a heterogeneous mixture of the reactants and resultants of the reaction CaO + H_{2}O + Cl_{2} <=> CaOCl_{2} + H_{2}O which is in equilibrium for the temperature and pressure obtaining during the process of manufacture. Under suitable physical conditions the chlorine content can be increased to 40-42 per cent but such a product is not so stable as those represented by the analyses on page 14 and which contain approximately 20 per cent of excess hydrate of lime. The stability of bleach depends upon this excess of base (Griffen and Hedallen[4]) and although magnesia can be partially substituted for this excess of lime, a minimum of 5 per cent of free hydrate of lime is required to ensure stability. On dissolving bleach in water the first action is the decomposition of calcium oxychloride into an equal number of molecules of calcium hypochlorite and calcium chloride. 2CaOCl_{2} = Ca(OCl)_{2} + CaCl_{2}. In dilute solution these salts are dissociated and hydrolysis tends to occur in accordance with the equations 2Ca(OCl)_{2} + 4H_{2}O <=> 2Ca(OH)_{2} + HOCl + HCl and CaCl_{2} + 2H_{2}O <=> Ca(OH)_{2} + 2HCl. Calcium hydrate and hydrochloric acid are both practically completely dissociated, i.e. there is a large and equal quantity of H^{.} and OH', and the product is much greater than K_{_w_} (ionic product of water), and hence there is a combination of these ions, leaving the solution neutral and no undissociated acid or base exists. This statement is only approximately correct as hydrochloric acid is slightly more dissociated than calcium hydroxide (ratio 9:8) and the solution is consequently slightly acid, i.e. the H^{.} concentration is greater than 1 × 10^{-7}. Hypochlorous acid is only very slightly dissociated, especially in the presence of the OCl' ion due to the dissociation of the Ca(OCl)_{2}, as compared with Ca(OH)_{2} and hydrolysis of the Ca(OCl)_{2} proceeds with increased dilution. The action is best represented by the equation 2Ca(OCl)_{2} + 2H_{2}O <=> CaCl_{2} + Ca(OH)_{2} + 2HOCl