18 The Philippine Journal of Science im 



although its order has not been determined experimentally. The 

 photolysis has been studied quantitatively by Lewis, (13) who 

 concluded that the reaction was probably monomolecular. 



When waters contain foreign substances either in solution or 

 in suspension, the decomposition rate of hypochlorites is gen- 

 erally markedly changed. Bhaduri(2) found that in the dark a 

 sodium hypochlorite solution was most stable when the con- 

 centration of sodium hypochlorite was 1.5-1.7 per cent; of salt 

 molecules, approximately 0.4 per cent. In the light, (13) alka- 

 line is more stable than neutral sodium hypochlorite solution. 

 Concentration and temperature have very little effect (6) on the 

 stability. Elements of the iron group accelerate decomposition ; 

 the presence of magnesium and aluminium increases the 

 instability when the alkalinity is low. Elmanowitsch and 

 Zaleski(4) found that acids increased, while alkalies decreased, 

 the amount of (calcium) hypochlorite decomposed (at boiling 

 temperature) by natural waters. Such factors as temperature, 

 alkalinity, and the presence of phenols and hydrogen sulphide 

 promote the decomposition of hypochlorites in sewage. (5) 



The accelerating influence of a high organic content in water 

 on the decomposition of hypochlorites has been much studied. 

 Asparagin, peptone and allied products, (8) albumin and its decom- 

 position products, (4) sewage, (5) urine, sweat, saliva, and body 

 products in general (10) have an especially great effect on the 

 chlorine consumption. Apparently there is no direct paral- 

 lelism between oxygen-consuming capacity (as measured by the 

 reduction of permanganate solution) and chlorine-consuming 

 power, (14) this no doubt due partly to the well-known inaccur- 

 acy of determinations of oxygen-consuming capacity in regard 

 to both quantity and kind of organic matter present in water, 

 partly to specific interaction between the substances in water 

 with chlorine. 



At first the disappearance of available chlorine from chlorin- 

 ated water or sewage is very rapid, but it soon becomes slow. 

 The reaction proceeds as though there were present, in some wa- 

 ters at least, substances which are so readily oxidized by chlorine 

 that they take it up before it can destroy the bacteria present. 

 Although the bactericidal action of chlorine occurs simultan- 

 eously with the chemical decomposition, the latter might pro- 

 ceed rapidly enough greatly to impede or even to nullify the 

 former. After the chlorine is once destroyed, bacterial growth 

 might proceed unchecked, which furnishes a possible explana- 

 tion for the repeatedly noted phenomenon — the great increase 



