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The products obtained from molten and aqueous SnF 2 : M I systems ( M = Na, K, Rb, and NH 4 ) have been studied. The Mossbauer data for phases with 1:1, 2:1, and 3:1 SnF 2 : M I molar ratios are reported. The M SnIF 2 phases show evidence of two tin sites, one of which has Mossbauer parameters attributable to an octahedral tin(II) environment. The materials obtained are all colored and the reasons for these colors are discussed.

A series of compounds, Cs3MIII2X9 (MIII = Sb and Bi, X = Cl or Br) are doped with impurity ions (Ba2+, Ca2+, Sn2+, Pb2+, Mg2+, Fe2+, Tl3+, In3+, Se4+). Lattices doped with Sn(II), Pb(II) and Se(IV) are colored. Sn-119m Mossbauer data are consistent with the donation of Sn-5s electron density from tin(II) to a conduction band to give a pseudo-tin(IV) electronic environment.

The electronic structure of the cubic phase of crystalline CsSnBr 3 has been investigated using X-ray photoelectron spectroscopy and a semiempirical energy band structure calculation. The observed semimetallic behaviour of this system and some similar crystalline trihalides in the cubic phase is related to the presence of a triply degenerate R 15 energy level in the calculated conduction band. The nonmetallic behaviour of the cubic phase of CsSnCl 3 may be accounted for by consideration of the spin-orbit splitting of this R 15 level.

The effect is studied of the presence of a wax binder on the flammability of, and smoke production from, systems containing acrylonitrile-butadiene-styrene copolymer, decabromobiphenyl and (a) antimony(III) oxide and (b) metastannic acid. The studies were carried out both by linear and by triangular designs and values were measured of flammability (by limiting oxygen index) and of smoke production (by maximum smoke density). Pelletisation of the additive metal compound or the addition of up to 3 phr of wax has virtually no effect on the properties of the system. It is thus shown that the use of up to 3 phr of a wax binder can reduce the health hazard arising from the use of powdered flame-retarding and smoke-suppressing additives.

Flame retardance and smoke suppression have been studied in three systems containing acrylonitrile-butadiene-styrene terpolymer, decabromobiphenyl, and (a) commercial metastannic acid, (b) laboratory-prepared metastannic acid and (c) anhydrous tin(IV) oxide. Values of limiting oxygen index and smoke density have been measured for a large number of compositions in each system. They have then been fitted by fourth-order polynomials and plotted in triangular diagrams. Optimum atomic ratios for all these synergistic systems were found to be: Br/Sn = 9, a value which is much higher than would be expected from stoichiometric calculations. The systems also possess significant smoke-suppressant effectiveness.