AN ADDRESS ON A NEW ANTISEPTIC DRESSING 317 



antiseptic in the dressing in spite of the discharge. How was this difficulty 

 to be overcome ? 



Now came to our aid our experience with the iodide of mercury and the 

 starch. Might it be that the particles of the double cyanide would attract 

 starch as those of the iodide had done ? It did not seem very likely, seeing 

 that cyanogen is not known to have the special affinity for starch that iodine 

 has. Still, I thought I would try the experiment. I prepared the double 

 cyanide by mixing a solution of the double cyanide of mercury and potassium 

 with a solution of sulpliate of zinc. I tried this with one of the ingredients 

 dissolved in a starchy solution, and, to my great satisfaction, I found that the 

 precipitated double cyanide left a supernatant liquor almost absolutelv free 

 from starch, and that the particles which thus fell, the double cyanide with the 

 starch associated, fixed themselves to a gauze in such a way that it did not 

 in the least dust when dry. Not only so, but immediately after being charged 

 with the precipitate diffused in water it might be washed in the wet state without 

 the double cyanide being washed out of it, so closely did the starch v particles 

 stick the double cyanide to the fabric. It is of great importance that in some 

 way or other the double cyanide should be washed, because at the same time 

 that an insoluble double cyanide is formed there are produced other double 

 cyanides which are soluble, and which are in the highest degree irritating ; 

 they must be washed out. 



Well, I thought I had thus attained my object, and that bv mixing starch 

 with one of the two solutions necessary for forming this double cvanide and 

 allowing the precipitate to deposit itself, then pouring in more water, and, 

 after precipitation, decanting and repeating the process another time, so as to 

 get rid of all the irritating soluble salts, and then diffusing the precipitate through 

 a gauze, I should have all that I desired. But when I tried to get this done bv 

 a manufacturer I found that I got blundering after blundering in such a way 

 as to make the thing practically hopeless. There was nothing for it but in 

 some way or other to get the double cyanide from the chemist as a definite 

 article, and then in some way devise a means of fixing that powder of the double 

 cyanide to the fabric. I therefore naturally tried whether a solution of starch 

 would answer this purpose, whether the starchy particles would associate them- 

 selves with the double-cyanide particles, not onlv in the nascent state, whicli 

 we had before tried, but also when the already formed double cyanide was mixed 

 with the starchv solution. I found that it did so ; that when a starch\- sohition 

 was stirred up witli the double cyanide in the jH'oportion (>f one j^art of starch 

 to two of cyanide, the starch was almost all precipitated, and the preci]"»itate so 

 formed adhered to the gauze in the most satisfactory manner. 



