Point-defect aggregates in (111) dislocation-free silicon single crystals grown by the float-zone (FZ) method have been studied by diffuse X-ray scattering (DXS) and compared with those in the Czochralskigrown (CZ) crystals. A two-axis X-ray diffractometer was used. It employs three monochromators in (+,-,-) setting to obtain a highly collimated and monochromatic Mo Ka, beam. DXS measurements were made around the 111 reciprocal-lattice point (r.I.p.) with K* along +[111] and +[01i]; K is the vector which joins the elemental volume of the reciprocal space under investigation to the nearest r.I.p. For FZ crystals for a given K* the DXS intensity was higher for 0 < 0B in comparison with that for 0> 0~ showing that the anisotropy (DXS Io>o,,-DXS Io

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The popular hepatoprotective Indian herbal drug Kalmegh (Andrographis paniculata) can be standardized by high pressure liquid chromatographic determination of its major active constituent, andrographolide. The leaves of the herb were found to contain the highest amount (2.39%w/w) of andrographolide and the seeds to contain the lowest. The technique was found to be much more sensitive and simple than the known spectrophotometric method.

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Densities, ρ, viscosities, η, and refractive indices, n D, for binary mixtures of hexane, decane, hexadecane, and squalane with benzene were measured over the whole composition range at 298.15 K and atmospheric pressure. The excess molar volumes, , and viscosity deviations, δη, were calculated from experimental measurements. These result were further fitted to the Redlich−Kister equation to estimate the binary coefficients and standard errors. The effects of chain length and branching of alkanes on and δη values have been discussed.

SynopsisThe thermal degradation of cellulose and its phosphorylated products (phosphates, diethylphosphate, and diphenylphosphate) were studied in air and nitrogen by differential thermal analysis and dynamic thermogravimetry from ambient temperature to 750°C. From the resulting data various thermodynamic parameters were obtained following the methods of Broido and Freeman and Carroll. The values of E, for decomposition for phosphorylated cellulose were found to be in the range 55-138 kJ mol-I in air and 85-152 kJ mol-' in nitrogen and depended upon the percent of phosphorus contents in the samples. The mass spectrum of cellobiose phosphate indicated the absence of the molecular ion, indicating that the compound was thermally unstable. The IR spectra of the pyrolysis residues of cellulose phosphate gave indication of formation of a compound having C = O and P=O groups. A fire retardancy mechanism for the thermal degradation of cellulose phosphate has been proposed.

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