[Footnote 1: Schloffel, Zeitschrift der K.K. geolog. Reichanstalt, 1866, p. 126.] * * * * * SULPHOCYANIDE OF POTASSIUM. The elements of cyanogen, combined with sulphur, form a salt radical, sulphocyanogen, C_{2}NS_{2}, which is expressed by the symbol Csy. The sulphocyanide of potassium, KCsy, is prepared by fusing ferrocyanide of potassium, deprived of its water of crystallization, intimately mixed with half its weight of sulphur and 17 parts of carbonate of potassa. The molten mass, after having cooled, is exhausted with water, the solution evaporated to dryness, and extracted with alcohol, from which the crystals of the salt are separated by evaporation. It is also made by melting the ferrocyanide of potassium with sulphide of potassium. It is a white, crystallizable salt of a taste resembling that of niter, soluble in water and alcohol, and extremely poisonous. It dissolves the chlorides, iodides, and bromides of silver, is, therefore, a fixing agent, but has not come in general use as such. Vogel speaks highly of it as an addition to the positive toning bath, although he prefers the analogous ammonium salt in the following formula: Chloride of gold solution.... (1:50) 3 c. cm. (46-1/5 grains). Sulphocyanide of ammonium ... 20 grammes (308 grains). Water........100 c. cm. (3 ounces 5 drachms 40 grains). _Ferrocyanide of Potassium_--K_{2}Cfy+3HO, or K_{2}C_{8}N_{3}Fe+3HO, is generally known by the name of yellow prussiate of potassa. It contains ferrocyanogen, a compound radical, consisting of 1 eq. of metallic iron and 3 eq. of the elements of cyanogen, and is designated by the symbol Cfy.