Correctness Of Use Research Articles

A modified nitroso-r method for the determination of cobalt in sea water

The existing colorimetric nitroso-R method for the determination of biologically important cobalt in sea water described by Thompson and Laevastu has been studied in detail, modified and improved. A procedure is recommended in which an approximately five-fold increase in sensitivity is achieved in the measurement of the nitroso-R chelate through close control of : pH, development time of complex, conditions for decomposition of excess reagent, and employment of a wavelength of 425 mμ. The size of the water sample required for an analysis is reduced from 10 to 21. For optimum results it was found necessary for a minimum period of 7 days to elapse following precipitation with sodium carbonate prior to filtration and analysis. A previously unreported salt effect in the procedure is described which requires either construction of a calibration curve from sea water spiked with cobalt or a correction in use of standards in distilled water. A precision was obtained with a 1–2% relative standard deviation throughout range of concentrations used, with an accuracy of 3.0% at 0.5 p.p.b.

Effect of humidity on flashover of air-gaps and insulators under alternating (50 c/s) and impulse (1/50 μs) voltages

The effects of humidity, for alternating voltages up to about 700 kV r.m.s. and impulse voltages up to about 1500kV, on gaps between 1m spheres, on rod-gaps, on suspension insulators and on pedestal-post insulators are described. Data are given on cylindrical-post insulators with alternating current and on point-plane gaps with impulse voltages.The data are limited but appear to be sufficient to justify conclusions which could affect practice, in particular, it appears that the a.c. flashover voltage of some gaps and insulators falls at high humidities, so that the negative correction in use at present should be replaced by a positive correction.The data for positive impulses, except for the sphere-gap, show that flashover voltages increase continuously with humidity. The effect with negative impulses is in some cases negligible.