The electrical and chemical efficiencies of the Haas and Oettel and Dayton cells, which contain carbon electrodes, are smaller than those containing platinum electrodes but for water sterilisation the carbon cells have been found to be more suitable. To prevent the action of magnesium salts on the platinum electrodes it is necessary to use a higher grade of salt or to provide means of purification. Because of the absence of a base and the presence of chlorides, electrolytic hypochlorite cannot be stored for more than a few hours without appreciable loss of titre. Unless used for the treatment of the effluent of a filter plant operated at a fairly constant rate a small storage tank is necessary to compensate for the irregular demand and to provide the head required by orifice feed boxes. Small variations can be made by regulating the flow through the cells but large ones are not compatible with efficiency, which is the highest under a constant load. Claims have been made that electrolytic hypochlorite is more efficient as a germicide than bleach when compared on the basis of their available chlorine content but no evidence of it has been produced. Bleach contains an excess of base, which retards the germicidal action, and electrolytic hypochlorite contains an excess of sodium chloride, which accelerates it (Race[4]) but the ultimate effect is the same with both. This is shown in Table XXIV. TABLE XXIV.[A]--COMPARISON OF BLEACH WITH ELECTROLYTIC HYPOCHLORITE ----------------+-------------------++------------------- | BLEACH. || ELECTROLYTIC | || HYPOCHLORITE. +-------------------++------------------- Contact Period. | Available Chlorine. Parts Per Million. +---------+---------++---------+--------- | 0.4 | 0.6 || 0.4 | 0.6 ----------------+---------+---------++---------+--------- Nil | 182 | ... || ... | ... 10 minutes | 130 | 10 || 120 | 8 1 hour | 66 | 1 || 60 | 0 2 hours | 3 | 0 || 1 | 0 3-1/2 hours | 0 | 0 || 0 | 0 ----------------+---------+---------++---------+--------- [A] Results are B. coli per 10 c.cms. Electrolytic hypochlorite has a greater germicidal velocity than bleach but the difference is so small as to be of no practical importance. Rabs[5] experimented with various hypochlorites but was unable to find any appreciable differences in their germicidal action.