The effect of sodium chloride on the bacteriological results, like that on the hydrolytic constant, is anomalous. Similar effects have been observed on the addition of this salt to phenol and other disinfectants. The _raison d'être_ of the increased activity is obscure but it is possible that the salt renders the organisms more susceptible to the action of the germicide. Ammonia, though decreasing the hydrogen ion concentration of bleach and other hypochlorite solutions, markedly increases the velocity of the reaction; chlorinated derivatives of ammonia (chloramines), which have a specific germicidal action, are formed. These will be discussed at length in Chapter IX, p. 115. Rideal[6] has shown that the addition of ammonia to sodium hypochlorite destroys the bleaching activity in acid solution. This has been found by the author to be also true for calcium hypochlorite (bleach). If the bleaching effect is due to oxidation, the oxidising power of hypochlorites must be considered to be destroyed by the addition of ammonia. The property of oxidising organic matter in water is also destroyed; this is well illustrated in Table II which shows the rate of absorption of chlorine and chloramine by the Ottawa River water. The water used in this experiment contained 40 p.p.m. of colour and absorbed 9.5 p.p.m. of oxygen (30 mins. at 100° C.). TABLE II.[A] ------------------+------------------------------------------------- | ABSORPTION OF AVAILABLE CHLORINE AT 63° F. Time of Contact +----------------------+-------------------------- Minutes. | Chlorine as Bleach. | Chlorine as Chloramine. ------------------+----------------------+-------------------------- Nil. | 10.00 | 9.98 5 | 6.50 | 9.98 10 | 5.91 | 9.90 20 | 5.18 | 9.90 40 | 4.47 | 9.84 60 | 3.90 | 9.84 80 | 3.65 | 9.84 20 hours | .... | 9.68 ------------------+----------------------+-------------------------- [A] Results are parts per million. From a consideration of these and other experiments made by the author in January, 1916, it became apparent that the nascent oxygen hypothesis entirely failed to explain the results obtained, and that they must be attributed to a direct toxic action of the chlorine or chloramine.