328 OBSERVATIONS ON THE CYANIDE OF ZINC AND MERCURY 



geously enhanced by the addition of a httle ammonia to the mixture, in the pro- 

 portion of I atom of ammonia (NH3=I7) to each atom of haematoxyhn (C 0H14 

 Og3H.O = 356). More than this proves prejudicial. The ammonia is added 

 in a dilute form, and it is convenient to have the dilution such that one 

 fluid drachm of the ammoniacal liquid shall correspond to one grain of haemia- 

 toxylin. The dye is further economized by allowing the ammoniated mixture to 

 stand for three or four hours and stirring it occasionally, so that the ingredients 

 may react thoroughly upon each other. If the mixture is filtered immediately, 

 there is considerable loss of colouring matter. The dyed salt having been drained 

 and dried at a moderate heat, is levigated, and may then be kept for any length 

 of time fit for use. When employed for charging a dressing, it is diffused by 

 means of pestle and mortar in solution of bichloride of mercury (i to 4,000) 

 in sufficient abundance to drench the fabric thoroughly, for which 4 imperial 

 pints to 100 grs. of the salt will be found adequate. This will give a percentage 

 of between 2 and 3 of the cyanide to the dry gauze. For reasons which I have 

 stated elsewhere,^ the gauze should always be used moist ; and if it be prepared 

 for immediate use, as by the dispenser of a hospital, the process of drying may 

 be omitted, the gauze, after being hung up for a while to drain, being deprived 

 further of superfluous moisture by placing it for a while in a folded sheet. It 

 may afterwards be conveniently kept moist by wrapping it in a piece of 

 macintosh cloth. When obtained dry from the manufacturer, it should be 

 moistened again with the weak corrosive sublimate solution before it is used. 



Vide Lancet, loc. cit. (p. 319 of tliis volume). 



