Elastic constants of sodium chlorate from 77 K to 350 K

The elastic constantsC ₁₁,C ₁₂ andC ₄₄ of sodium chlorate single crystal have been evaluated using 10 MHz ultrasonic pulse echo superposition technique. The values areC ₁₁=4.90,C ₁₂=1.39,C ₄₄=1.17 (× 10¹⁰ N/m ²) at 298 K and 6.15, 2.16, 1.32 (×10¹⁰ N/m ²) at 77 K. The data agree well with the values measured earlier up to 223 K. Brief mention is also made of the low temperature bonding problems in these soft crystals.     

Electrical transport and high pressure studies on bulk Ge20Te80 glass

The electrical resistivity of bulk Ge₂₀Te₈₀ has been measured as a function of pressure and temperature. At 5 GPa, an amorphous semiconductor-to-crystalline metal transition has been observed. The sample recovered from the high pressure cell, after the application of 7 GPa, has a face-centred cubic structure with a lattice constant of 6·42 A. In crystalline sample, the semiconductor-to-metal transition occurs at 7 GPa. The thermoelectric power has also been measured for glassy samples in the temperature range 300–240 K.     

Stannoxanes and phosphonates: New approaches in organometallic and transition metal assemblies

Phosphonate ligands, [RPO₃]^2-, are extremely versatile in the assembly of multi-tin and multi-copper architectures. We have used organostannoxane cores for supporting multi-ferrocene and multi-porphyrin peripheries. The copper-metalated multi-porphyrin compound is an excellent reagent for facile cleavage of DNA, even in the absence of a co-oxidant. Reaction oft-BuPO₃H₂ with Cu(C10₄)₂. 6H₂O in the presence of 2-pyridylpyrazole (2-Pypz) leads to the synthesis of a decanuclear copper (II) assembly.     

Elastic constants of galena down to liquid helium temperatures

The elastic constants of single crystal galena have been determined from the measured ultrasonic velocities down to liquid helium temperature. A cryostat incorporating an arrangement to inject the liquid bonding material at low temperature is described. At 5 K, the values of elastic constants are C₁₁=14.9₀, C₁₂=3.5₁ and C₄₄=2.9₂×10¹⁰ N/m².     

Study of effects of dopants on structure of vitreous semiconductors (GeSe3.5)100-xMx (M = Bi,Sb) using high pressure techniques

An investigation of the problem of controlled doping of amorphous chalcogenide semiconductors utilizing a Bridgman anvil high pressure technique, has been undertaken. Bulk amorphous semiconducting materials (GeSe_3.5)_100-x doped with M = Bi (x = 2, 4, 10) and M = Sb (x = 10) respectively are studied up to a pressure of 100 kbar down to liquid nitrogen temperature, with a view to observe the impurity induced modifications. Measurement of the electrical conductivity of the doped samples under quasi-hydrostatic pressure reveals that the pressure induced effects in lightly doped (2 at % Bi) and heavily doped (x = 4, 10) semiconductors are markedly different. The pressure effects in Sb-doped semiconductors are quite different from those in Bi-doped material.     

Microdetermination of indoles with N-bromoacetamide in acetic acid medium

Summary A titrimetric method for the microdetermination of indole and its derivatives withN-bromoacetamide is described. It has been observed thatN-bromoacetamide brominates the compound containing indole nucleus in the presence of acetic acid. The usual reaction time is 15 minutes and the reaction is carried out at room temperature. The relative errors are less than ±1.5% at the mg level.

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Zusammenfassung Die maßanalytische Bestimmung von Indol und seinen Derivaten mitN-Bromacetamid wurde beschrieben. Dieses Reagens bromiert in Gegenwart von Essigsäure indolhältige Verbindungen innerhalb 15 min bei Zimmertemperatur. Der rel. Fehler ist geringer als ±1,5%.

     

New band systems of NiBr molecule in visible region

Thermal emission spectrum of NiBr molecule excited by vacuum graphite tube furnace revealed the existence of ten new band sub-systems in the region λλ 5540-4720 Å which were attributed toA→X,B→X,C→X andD→X transitions. Vibrational analysis was carried out for each of the systems mentioned above.A ² Δ has been suggested as the ground state of NiBr molecule with an electronic interval of about 533 cm^?1. Transitions responsible for NiBr spectrum appear to be of the type²π–²Δ and²Δ–²Δ.     

The elastic constants of isomorphous sodium bromate and sodium chlorate from 77 to 350 K

The elastic constants of NaBrO₃ and NaClO₃ are evaluated from ultrasonic velocity measurements using pulse superposition techniques. The values of C₁₁, C₁₂ and C₄₄ for NaBrO₃ at 298°K are 5.57₈, 1.70₅, 1.51₀ (x 10¹⁰ N/m²) and for NaClO₃ the values are 4.89₇, 1.38₉, 1.17₄. The values at 77°K are respectively 6.35, 1.98 and 1.65 for NaBrO₃ and 6.15, 2.16 and 1.32 for NaClO₃.