90 BIOLOGY AND TECHNIQUE 



Hypochlorous acid may also decompose with the liberation of 

 oxygen as shown in the following equation: 



2HC10 == 2HC1 + 2 



It is conceivable that some of the disinfecting value of chloride of 

 lime and hypochlorites in general is really due to the vigorous 

 oxidizing action resulting from this decomposition. On the other 

 hand, there is much evidence to show that chlorine may attack the 

 protein molecule directly by replacing "H" in the amino groups, 

 thus: 



_R__CO NH R + C1 = R CO NCI R- +H 



The chloramines thus formed seem to be toxic and result in the 

 death of the bacteria. Bleaching powder is readily soluble in about 

 twenty parts of water. Its bactericidal action depends on the 

 hypochlorous acid formed. After water precipitation, an efficient 

 dosage is 10 pounds to the million gallons. The high germicidal 

 action of chloride of lime, together with its relatively low cost, 

 suggest its use as a wound dressing. Solutions of calcium or sodium 

 hypochlorite were found to be too irritating to be practicable, owing 

 to the alkalinity of any available preparations. Recently, however, 

 it has been possible to prepare neutral, and comparatively non- 

 irritating solutions of sodium hypochlorite by several different 

 methods. 



Dakins Solution. The following detailed descriptions of the prepara- 

 tion of Dakin's solution and its titration are taken from the Medical War 

 Manual, Number 6, Laboratory Methods of the United States Army, published 

 from the Surgeon General's Office, and are given directly as printed in this 

 Manual, because the method was standardized for Army use in this way 

 during the war. The description which follows is taken verbatim from 

 this Manual. 



Preparation from Bleaching Powder. Dakin's Original Method. A 

 strong solution of hypochlorite is prepared by decomposing 150 grams 

 bleaching powder (about 25 to 35 per cent available chlorine) with 105 

 grams dry sodium carbonate (122 grams monoliydrate (Na.,CO,H,0) or 284 

 grams washing soda (Na 2 C0 8 10H 2 0). The mixture is very thoroughly 

 shaken, both to make good contact and to render the precipitated calcium 

 carbonate granular and promote its settling. It is then allowed to stand 

 quietly and after half an hour the clear liquid is siphoned off from the 

 precipitate and filtered through paper or a cotton plug. 



