A simple and sensitive analytical method for the determination of antimony in environmental and biological samples.

The results of a study and application of leucocrystal violet for the determination of antimony in parts per million levels is described here. The proposed method is based on the reaction of antimony(III) with acidified potassium iodate to liberate iodine. The liberated iodine selectively oxidizes leucocrystal violet to crystal violet dye. The formed dye shows maximum absorbance at 590 nm. The color system obeys Beer's law in the concentration range from 0.4 - 3.6 microg antimony per 25 ml of final solution. The molar absorptivity and Sandell's sensitivity were found to be 7.32 x 10(5) l mol(-1) cm(-1) and 0.0016 microg cm(-2), respectively. All variables were studied in order to optimize the reaction. The proposed method is satisfactorily applicable for the analysis of antimony in various environmental and biological samples. The method is simple, highly sensitive, accurate and reliable.     

Observation of inter-grain Josephson effects in Y-Ba-Cu-O samples

Josephson effects have been observed in bulk samples of Y-Ba-Cu-O. The magnitude of the zero-voltage current is found to change systematically with externally applied small magnetic fields of a few mG. It is also found to vary when samples are irradiated with microwaves. These observations suggest the presence of inter-grain Josephson junctions.     

Collapse of square and rectangular tubes in transverse loading

Summary Analysis of the in plane lateral collapse of square and rectangular cross-section tubes is presented by considering the out-of-straightness of horizontal and vertical arms, corner radius, friction between the platens and the deforming specimen and instability of vertical arms. Results of collapse load for tubes of aluminium and mild steel, thus computed, are presented for some typical tube geometrics, and influence thereon of various parameters considered is discussed. Experiments were conducted wherein tubes of square and rectangular cross-sections of both the materials were laterally compressed between two parallel platens in an Instron machine. The observed collapse loads compare very well with the corresponding computed values.

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Kollaps von vertikal belasteten Rohren mit quadratischem und rechteckigem Querschmitt

Übersicht Der Kollaps von Rohren mit quadratischem und rechteckigem Querschnitt, welche senkrecht zur Achse belastet werden, wird untersucht, wobei schiefe Vertikal- und Horizontalstege, gerundete Profilecken, Reibung zwischen Belastungsplatten und Rohr sowie die Stabilität der Vertikalstege brücksichtigt werden. Die Kollapslast wird für Aluminium und Weichstahl und einige typische Rohrgeometrien ermittelt und der Einfluß verschiedener Parameter wird untersucht. Die Experimente wurden auf einer Instron-Maschine durchgeführt, wobei Rohre mit quadratischem und rechteckigem Querschnitt aus beiden Werkstoffen zwischen zwei parallelen Platten quer zur Achse komprimiert wurden. Es konnte eine gute Übereinstimmung zwischen den Resultaten aus Experiment und Rechnung festgestellt werden.

     

Kinetics and mechanism of the oxidation of acetaldehyde by chromic acid in perchloric acid

Summary The oxidation of MeCHO by chromium(VI) has been studied in HClO₄ medium over a wide range of experimental conditions and has been found to obey the rate law;v=k[MeCHO][HCrO ₄ ^– ][H⁺]. The calculated H and-S values for the reaction are 30±2kJ mol^–1 and 171±7J mol^–1deg^–1, respectively. The mechanism is discussed in terms of carbon-hydrogen bond cleavage.