space-group P6122-D,2. The structure w a s determined from a Patterson projection, and refined by threedimensional least squares, the final R being 0.090 for 193 reflections.Gold trifluoride is a fluorine-bridged polymer, with gold atoms linked to square-planar arrangements of fluorine atoms. Each square-planar unit is linked to two adjacent units by cis fluorine bridges, giving an infinite hexagonal helix, with AU-F (bridging) = 2.04 A, Au-F (non-bridging) = 1.91 A, Au-F-Au = 11 6". Weak cross-linking between chains, with Au * -F = 2.69 8, completes a tetragonally-elongated octahedral environment around each gold atom.Gold trifluoride is the least densely packed of the noble-metal trifluorides. This and the geometry of the fluorine ligand co-ordination are consistent with the antibonding nature of one of the electron pairs of the low-spin da electron configuration of gold(ii1).Vancouver 8, B.C., Canada GOLD trifluoride was first prepared in 1949 by Sharpe by pyrolysis at 180" of the adduct BrF,,AuF,, derived by dissolving gold metal in bromine trifluoride. Material so prepared usually contains some bromide,l and is weakly paramagnetic.2 Analytically pure gold trifluoride is diamagnetic, so the ds Auxn electron configuration must be of low spin. A crystal-structure determination of AuF, was first undertaken by Asprey, Jack, Kruse, and Maitland,3 but the absence of satisfactory single-crystal results prevented the completion of their structure analysis. Recently, we have prepared small single crystals of excellent quality for X-ray diffraction work and have completed the AuF, structure analysis. We have employed the accurate unit-cell dimensions of Asprey et aL3 and their value for the measured density of AuF,.

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SYNOPSISFree radical copolymerization of ethyl methacrylate (EMA) and acrylamide ( AA) was carried out in the presence of 2,2'-azobisisobutyronitrile ( AIBN ) in dimethyl formamide (DMF) at 60°C. The percentage composition of the copolymers were established by elemental analysis. The copolymerization reactivity ratios were determined by both FinemanRoss (F-R) and Kelen-Tudos (K-T) methods. The copolymers were characterized by IR, 'H-NMR, thermal, and dielectric studies. Glass transition temperatures ( Tg) have been determined by DSC. The solubility parameter of this copolymer was evaluated by studying the intrinsic viscosity in different solvents. I NTRO DUCT10 NAcrylic copolymers have acquired prime importance in various avenues of industrial application^.'-^ They serve as basic materials for the preparation of formulations that are used as base and top coats in leather industry. Saini et al.4 studied the free radical copolymerization of acrylamide ( AA ) -methyl methacrylate and AA-styrene. Copolymerization of acrylamide with styreneY5 n -butyl acrylate, acrylic acid,7 methyl vinyl ketone,' acrylo nitrile,g and methacrylic acid" were also studied by various workers in the past few years. In our earlier paper, l1 we determined the reactivity ratios of methacrylamide with ethyl methacrylate (EMA) . In the present investigation, reactivity ratios, thermal electrical properties, and solubility parameters of EMA-AA copolymer systems are studied. EXPERIMENTALEthyl methacrylate (Fluka) was purified from inhibitor by washing with 5% sodium hydroxide in water, and dried over calcium chloride and distilled twice under reduced pressure. Acrylamide was crys- tallized from chloroform. 2,2'-Azobisisobutyronitrile ( AIBN) (Fluka) was crystallized from methanol. N,N-Dimethyl formamide (DMF) (Qualigens) was reagent grade product and was dried and purified by distillation before use.All experiments were performed in glass tubes filled with dry monomers, solvents, and initiator. The tubes were then sealed in a nitrogen atmosphere and introduced into the thermostat at desired temperature. The reaction was allowed to go for less than 10% conversion, the reactions were stopped by adding excess volume of water as nonsolvent, and the copolymers were precipitated, washed thoroughly with ether and hexane to remove DMF and unreacted monomer. Reprecipitation was done from acetone solution. The total concentration was kept constant at (1.6 mol/L monomers). The initiator was used at 0.6 g/L solvent.The IR spectra of the copolymers were recorded with Perkin-Elmer model spectrophotometer.'H-NMR spectra were recorded from CDC13 solution using a EM-360 60 MHz spectrometer. The glass transition temperatures, Tg , of the copolymers were determined by differential scanning calorimetry (DSC) at a heating rate of 8OC/min. Thermogravimetric analysis (TGA) was carried out using a Dupont 900 thermobalance in air at a heating rate of 8"C/min.The integral procedural decomposition temperature (IPDT)12 values were determined from a 1521

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