GUTHRIE ON THE BZSULPHIDE OF IODINE. VIIT.-On the Bisukhide of Iodine. BY FREDERICK GUTHRIE. AN examination of the action of certain compound halogens on some of the olefines has led me to consider incidentally the preparation of some of the compound halogens in the pure state. Of compound halogens while the constitution of none is more invariable and definite than that of the bisiilphide of chlorine,- the bisulphide of iodine can scarcely be said to have been prepared notwithstanding the strong analogy between chlorine and iodine. That iodine combines with sulphur is well known; that such combination is attended by the liberation of heat is equally well established; and since homogeneous mixtures of the two may be prepared in all proportions it is clear that a substance having the percentage composition of the bisulphide of iodine may be formed.Bodies so formed have little or no title to the name of chemical compounds. If we remember on the one hand the fact which I have abun-VOL. XIV. F GUTHRIE ON THE BISULPHIDE OF IODINE. dantly proved on former occasions that an equivalent of bisulphide of chlorine functions as two equivalents of chlorine or as some chemists would express it that the rnoleciile of bisulphide of chlorine is biatomic; and if we further remember that at least two equivalents of chlorine or of zinc are required to recompose iodide of ethyl according to the equations- (l)*C,H,I + 2C1 = C,H,Cl + IC1 (2) C,H,I + 2Zn = C,H,Zn + ZnI we must be prepared to anticipate the analogous re-action- (3) C4H51 + S,Cl = C4H,Cl + S,I This the more because in the case of certain compounds such as NaSn we find-(4) C,H,I + NrtSn = C,H5Sn + NaI.The method I employ for the preparation of the bisulphide of iodine is in fact based upon the validity of equation (3). Recornpositions quite akin to (3) are suffered by the iodides of methyl and of amyl; whence we may assert the general equation-(5) C,H,+,I + S,C1 = C,H,+,Cl + 3,I. For obvious reasons the ethyl-compound is preferred The reciprocal action of iodide of ethyl and bisulphide of chlorine is perhaps as interesting in its manner as in its result. The two liquids may be mixed in all proportions without a greater change in colour than is due to the dilution of the coloured sulphide by the colourless iodide ;neither is heat liberated nor other immediate token given of chemical change taking place.The change appears to be complete in about twelve hours. If the vessel be ogen to the air the chloride of Gthyl evaporates as it is formed leaving the bisulphide of iodine in magnificent crystals contami- nated however by the products of the action of the moisture of the air upon the bisulphide of chlorine. For this reason the process is best conducted in a hermetically sealed tube. The CO-reagents are used in the proportions shown by the equation-& very slight excess of the iodide being added. * Equation (1)expresses only the initial recomposition-the ultimate prahcts are HCl,ICl and chlorine substitution-products of C,H,Cl.GUTHRIE ON THE BISULPI-IIDE OF IODINE. On opening a tube so charged which has been left over night and applying the heat of the hand the chloride of ethyl escapes. A gentle heat suffices to expel the residual iodide of ethyl-where-upon the bisulphide of iodine is left in the form of' fine tabular crystals of the lustre of iodine and in a state of absolute purity. Although the exact composition of the substance may be fairly deduced from its synthesis it was submitted to analysis in the following way 0.3270 grm. was heated in a combustion-tube with nitrate of potash and carbonate of soda whereby the iodine and sulphur were converted respectively into iodide and sulphate of potassium. They were then estimated in the usual way Calculated. Found. S .2O*J3 20.28 I 7'9.87 7'9.81 100*00 100.09 Though in this note this curious re-action is considered as a means of preparing the compound halogen S,I it is perhaps of equal interest as offering a method for preparing an organic chlo-ride from its iodide ;-a problem hitherto difficult and cumbrous in solution albeit its inverse is often easy and of frequent occurrence.