764 A MANUAL OF BACTERIOLOGY 



objects are not likely to be injured, the hypochlorites are 

 among the best of known disinfectants, provided they 

 are used fresh. The slow addition of hydrochloric acid, 

 yielding nascent chlorine, increases the activity of a hypo- 

 chlorite considerably. A solution of iodine is now used 

 for skin disinfection in surgical practice. Iodine tri- 

 chloride is a powerful disinfectant, of which the use has 

 been suggested, among other purposes, for the sterilisation 

 of water. Nessfield suggested the use of chlorine for 

 sterilising water on the large scale, and iodine for the same 

 purpose on the small scale. Chloride of lime or other 

 hypochlorite and chlorine gas are now being extensively 

 used for sterilising water on the large scale (p. 724). 



Hypochlorites, e.g. Eusol and Dakin's solution, have 

 been much used of late for the treatment of septic 

 gun-shot and shrapnel wounds, as in the Carrel-Dakin 

 system. Dakin's solution which is used contains 0-5-0-6 

 per cent, of sodium hypochlorite. It is prepared as 

 follows : 



One hundred and forty grams of dry sodium carbonate 

 (Na 2 C0 3 ), or 400 grams of the crystallised salt (washing 

 soda), are dissolved in 10 litres of tap water, arid 200 grams 

 of chloride of lime (chlorinated lime) of good quality are 

 added. The mixture is well shaken, and, after half an 

 hour, the clear liquid is siphoned off from the precipitate 

 of calcium carbonate and filtered through a plug of cotton ; 

 40 grams of boric acid are added to the clear filtrate, and 

 the resulting solution is ready for use. A slight additional 

 precipitate of calcium salts may slowly occur, but it is of 

 no significance. The solution should not be kept longer 

 than one week. The boric acid must not be added to the 

 mixture before filtering, but afterwards. 



When a hypochlorite acts upon an organic substance 

 containing the = NH group, the first reaction consists 

 in the replacement of hydrogen by chlorine and the 



