The polymorphism of phenobarbitone has been investigated using infrared spectroscopy, X-ray diffraction and differential scanning calorimetry. Eight crystalline modifications have been isolated and shown to have distinguishable infrared absorption spectra and X-ray powder diffraction patterns. Other forms were found to be present in mixed crystals and molecular compounds obtained from mixtures of phenobarbitone with other barbiturates. Differential thermograms of three forms of thialbarbitone are also given.

The charucterisarion of hydrocarbon and natrrral waxes by dr#i~rent ial scatinirrg culorinietry is described. It is shown that the determination of the melting, cooling and remelting curves of a wax, and comparison with the corresponding curves of authenticated waxes, affords a rapid arid valuable method Jiir the identification of many waxes. Heats oj'transition of many waxes are also givcw.

The thermal decomposition of sodium dithionite (Na2S2O4) in the solid state was investigated by differential scanning calorimetry and the exothermic heat of decomposition was determined. The effect of isothermal pretreatment at various selected temperatures on the subsequently determined decomposition temperature was studied, together with the effect of sample weight on the decomposition temperature and degree of exothermicity.

The cobalt(II), cadmium(II), copper(II), mercury(II), nickel(II) and zinc(H) complexes of diethyldithiocarbamic acid were prepared and investigated by TG, DSC thin-layer chromatography and gas-liquid chromatography. Heats of fusion were determined.Diethyldithiocarbamic acid (DDC) readily forms complexes with S C2H5-If ~)N -C-SI-I C21-I~/ monovalent, divalent, and trivalent metal ions, having the general formula M(DDC)n, where n is the positive charge of the metal ion. D'Ascenzo and Wendlandt [1 ] have repoited the preparation and thermal properties of hydrated forms of cohalt(II), nickel(II), copper(II), zinc(II), cadmium(ID, silver(I) and mercury(II) complexes of DDC. These workers concluded that most of these metal chelates were highly volatile and therefore suggested their separation via the gas chromatographic technique. We have attempted to reproduce the preparations and thermal characteristics of these hydrated metal complexes but can find no evidence of hydrate formation and from our thermal data we do not reach the same conclusions as D'Ascenzo and Wendlandt [1] regarding the volatility of these particular metal complexes. We wish to report our studies on the preparation of these particular metal chelates and their investigation by thermogravimetry (TG), differential scanning calorimetry (DSC), thin-layer chromatography (t.l.c.) and gas-liquid chromatography (GLC). Experimental Thermal instrumentationThe TG curves were recorded on a Du Pont Model 950 Thermobalance using a dynamic nitrogen furnace atmosphere. Sample sizes ranged from 9.9 to 10.1 rag;-a heating rate of 10 ~ per min was employed. DSC curves were recorded on a Perkin-Elmer DSC-1B with a dynamic nitrogen atmosphere. Sample sizes ranged from 3 to 10 mg and a heating rate of 8 ~ per rain was employed. The temperature scale of the DSC was calibrated using pure Indium metal (m.p.