SVLPHOCYAN'OGEN A THE SULPHOCY'ANIDES. The former of these terms is given to a monobasic radical, or CyS,, which has never yet been isolated, but which forms an acid compound, known as hydrosulphocyanic acid (II,CNS,), with hydrogen, and yields numerous metallic salts. These salts, known as sulphocyanides, may be represented by the general formula, where M represents any metal. The sulphocyanides of potassium, sodium, and ammonium are crystallizable and soluble in water; those of the heavy metals are comparatively insoluble. These salts do not possess the poisonous character of the cyanides. Sulphocyanide of potassium (K,CyS2) is anhydrous, but very deliquescent, and occurs in long streaked colorless prisms, some what resembling niter both in appearance and taste; it is extremely soluble in water, and fuses on the application of a gentle heat. The sulphocyanide of mercury is a white powder which possesses the property of swelling or growing in size to an almost incred ible degree when moderately heated, so as to decompose it into a mixture of mellon with a little sulphide of mercury. The resulting mass often assumes a most
fantastic shape, and is sufficiently coherent to retain its form: it is of a yellow color externally, but black within. It is this sulphocyanide which is the ingredient of the well-known toy known as " Pharaoh's serpents." Each serpent consists of a little cone of tinfoil, resembling a pastille in shape, and filled with the above-named compound. On lighting the cone at the apex, there begins to issue from it a thick serpent-like coil, which continues twisting and increasing in length to an extraordinary degree, the ser pent-like shape resulting from the salt being burned in the tinfoil cone. The compound is readily obtained by•precipitating a strong solution of pernitrate of mercury with sulpho cyanide of ammonium, which is most cheaply prepared by Mr. Wood's method from btsulphide of carbon. •