330 NOTE ON THE DOUBLE CYANIDE OF MERCURY 



Gauze may be charged by drawing it in several thicknesses through a 5 per 

 cent, solution of carbolic acid in which the dyed cyanide is diffused in sufficient 

 quantity to be about 3 per cent, of the weight of the dry gauze, the liquid being 

 constantly stirred to prevent deposition of the heavy salt. 



Old rags or other absorbent fabrics can be readily charged by dipping several 

 la3^ers of them in the 5 per cent, solution of phenol, and dusting one surface 

 with an excess of the powder, which is then diffused by folding the mass, and 

 pressing it till a pretty uniform tint is produced. The absolutely unirritating 

 character of the double cyanide makes a little excess of it in any parts a matter 

 of indifference. 



The solution of carbolic acid is used because the cyanide powder is much 

 more readily diffused in it than it is in water, while it destroys any microbes 

 present in the gauze as it comes from the manufacturer. The solution of phenol 

 has the further advantage that it does not receive the slightest colour from the 

 dyed cyanide, so that the depth of tint of the fabric charged with it is in exact 

 proportion to the amount of salt it contains. 



The gauze, as supplied by the chemist, is dry, and having lost the carbolic 

 acid used in charging it, may have been subsequently contaminated with septic 

 material. The double cyanide, though very remarkable for its inhibitory power 

 over bacteric development, is without efficacy as a germicide ; and the microbes 

 in the contaminating material would be free to develop in the deep parts of the 

 gauze as soon as the cyanide in them had been exhausted. In case of moderate 

 discharge this would probably never occur, thanks to the slight solubility of the 

 salt and its secure fixation by the dye. But in case of copious effusion of blood 

 and serum, the salt would in time be exhausted, and the microbes in the infective 

 material would be free to develop. In order to guard against this risk, the 

 dressing may either be damped throughout with the carbolic lotion, or, as ample 

 experience has proved to be sufficient, a portion of the gauze in several layers, 

 soaked with the lotion, may be applied over and around the wound and the rest 

 of the dressing used dry. 



Bichloride of mercury must not be emplo3^ed for moistening the gauze, 

 because it forms with the double cyanide a triple com.pound which is both' 

 feebly germicidal and highly irritating. 



The double cyanide might, I believe, be very satisfactorily used in military 

 practice as a first dressing, by dusting it over the wound with a pepper box, and 

 covering with any absorbent material that might be at hand. The salt might 

 be used with the utmost freedom, as experience has shown that there is no risk of 

 its producing poisonous effects. Some surgeons who undertook to use the cyanide 

 in this way in the late South African war, had unfortunately no opportunity 



