Before considering the "modus operandi" of chlorine and hypochlorites, it will be advisable to take up the composition of the latter substances and particularly that of "bleach." Bleach is manufactured by passing chlorine gas over slaked lime and the ensuing reactions are often represented by the equation Ca(OH)_{2} + Cl_{2} = CaOCl_{2} + H_{2}O. This represents the substance formed as a pure oxychloride of calcium which contains approximately 50 per cent of chlorine, but the article commercially produced never contains this amount of chlorine, the usual percentage being from 35-37. The general composition of commercial bleach is fairly uniform. This is shown in the following analyses of which two are of German bleach examined by Lunge and one of Canadian manufacture analysed by the author. -------------------------------+----------------+-------- | Lunge. | Race. -------------------------------+--------+-------+-------- | % | % | % Available chlorine | 37.00 | 38.30 | 37.50 Chlorine as chlorides | 0.35 | 0.59 | 0.52 Chlorine as chlorates | 0.25 | 0.08 | 0.18 Lime | 44.49 | 43.34 | 44.12 Magnesia | 0.40 | 0.31 | 1.28 Iron oxide | 0.05 | 0.04 | 0.11 Alumina | 0.43 | 0.41 | 0.46 Carbon dioxide | 0.18 | 0.31 | 0.22 Silica | 0.40 | 0.30 | 0.52 Water and undetermined | 16.45 | 16.32 | 15.09 -------------------------------+--------+-------+-------- From these analyses the constitutional of commercial bleach might be represented by the formula 4CaOCl_{2}·2Ca(OH)_{2}·5H_{2}O which assumes it to contain: 68.0 per cent of calcium hypochlorite, 20.0 per cent of calcium hydroxide, and 12.0 per cent of water. In this formula calcium hypochlorite has been written CaOCl_{2}, but this substance actually contains one atom of oxygen less than the true hypochlorite, which has the constitutional formula ClO-Ca-OCl. This difference led some of the earlier chemists to regard CaOCl_{2} as a mixture of equal molecules of calcium chloride and calcium hypochlorite (CaCl_{2} + Ca(OCl)_{2} = 2CaOCl_{2}), but it has been definitely established that no calcium chloride exists in the free state in dry commercial bleach.