The thermal behaviours of sulphur, selenium and their mixtures have been studied over the range 40–450‡. It has been shown that the polymerization threshold temperature of sulphur,TØ, decreases with increasing selenium content and follows the equilibrium copolymerization model proposed by Tobolsky and Owen. The formation of octa-atomic species Se8−xSx, where 8 >x > 4, takes place only after sulphur is in the liquid state. The rate of polymerization is enhanced by the addition of increasing amounts of selenium and this is reflected in the higher polymerization peak temperatures. The X-ray powder diffractograms show that all the sulphur-selenium melts belong to the same phase as that of SeS, though the constituent atoms are randomly distributed.
A radiochemical method for the determination of fluoride has been developed. The effect of fluoride on the extraction of the Fe/III/ thiocyanate complex into TBP in nitrobenzene has been utilized. Microgram quantities of F– have been determined. Effect of diverse ions has also been reported. The method is applied for the determination of F– in a natural sample of apetite.
Authors:S. Krishnan, E. Cortés, V. Cassorla, L. Muñoz, and N. Gras
Mercury pollution in the industrial environment of Chile has been studied using hair as a monitor. Data from samples representing people living in the non-polluted and also from the polluted areas show that, hair is an effective and convenient indicator of environmental mercury pollution in Chile. A major source of mercury pollution and its transport is contaminated water. Hair is found to concentrate mercury from water to an extent of 80 to 500 fold increase in hair concentration. This absorption occurs in a contact time of 24 h and thus provides a means of treating mercury containing water to reduce the mercury to acceptable levels. The capacity of hair for this purpose is about 0.2% which means that, with a kilogram of hair /valued at less than 25 cents/ nearly 20.000 litres of contaminated water /at 0.1 ppm mercury/ can be treated. This is an inexpensive and convenient alternative to conventional ion-exchange processes which are generally very expensive, particularly for developing countries.
Authors:Hrudananda Jena, R. Venkata Krishnan, R. Asuvathraman, K. Nagarajan, and K. V. Govindan Kutty
Ba10−xCsx(PO4)6Cl2, (x = 0, 0.5) chloroapatite ceramics were prepared by sonochemical method of synthesis. The measured room temperature lattice parameters of Ba10 (PO4)6Cl2 and Ba9.5Cs0.5 (PO4)6Cl2−δ are practically the same; that is, a = 10.26 (8), c = 7.65 (7) and a = 10.27 (7), c = 7.65 (5), respectively. Heat capacity measurements were carried out on these materials by differential scanning calorimetry (DSC) in the temperature range 298–800 K. The heat capacity values of Ba9.5Cs0.5(PO4)6Cl2−δ are found to be slightly higher at all temperatures than those of Ba10(PO4)6Cl2. From the heat capacity data, other thermodynamic functions such as enthalpy and entropy increments were computed. The heat capacity values of Ba10(PO4)6Cl2 and Ba9.5Cs0.5(PO4)6Cl2−δ at 298 K are 0.3912 and 0.4310 J K−1 g−1, respectively. Thermal expansion property of the doped and undoped barium chloroapatites was measured by using a home built dilatometer which uses LVDT as displacement sensor. The bulk thermal expansion of Ba10(PO4)Cl2 and Ba9.5Cs0.5(PO4)Cl2−δ is observed to be about 0.9% in the temperature range of 298–973 K.