Polarographic Behaviour of the Hexa-ammine-chromium(III) Ion: Role of Hydrogen Ions
HEXA-AMMINECHROMIUM(III) ion in acetate buffer solutions is reduced at the dropping mercury electrode, and gives two polarographic waves. The first wave, which is well defined, is considered to be a one-electron reduction of Cr(III) to Cr(II)1. Its half-wave potential at 25° C was found to be −0.970 V versus saturated calomel electrode in 0.1 M acetate buffer solution which contained 0.9 M potassium chloride and 0.005 per cent gelatin (Fig. 1, curve a). The limiting current of this wave was diffusion-controlled and proportional to the concentration of the complex ion up to 5 mM. Both the half-wave potential and the diffusion current remained constant when the pH was varied from 4.5 to 5.45. No change was observed when potassium chloride was replaced by ammonium chloride at the constant ionic strength. The plot of log ī/(īd − ī) versus E, where ī means the average current, īd the average diffusion current, and E, the potential of the dropping mercury electrode, gave a straight line with a reciprocal slope of 64 mV, whereas the examinations with Kalousek's circuit and alternating current polarograph showed that this wave has nearly irreversible character.
Polarographic Studies of Metallic Complexes. II. Isothiocyanato-ammine and Related Complexes of Chromium (III)
1. In neutral and unbuffered solution of 0.1 F potassium chloride, 0.1 F potassium thiocyanate, or 1 F potassium thiocyanate, the complex ion, [Cr(NH3)n(NCS)6−n]n−3 and [Cr en3]3+ were all reduced irreversibly in two steps at the dropping mercury electrode. The first diffusion current corresponds to the reduction, chromium(III)→chromium(II), and the second to the reduction, chromium(II)→chromium(0). 2. In the solution of 0.1 F potassium chloride, the polarograms of [Cr en2X2]+ type complexes show three waves. Each of the first two waves, corresponding to a gain of one electron, represents the reduction of chromium(III) to chromium(II) and the last wave, corresponding to a gain of two electrons, represents the reduction to the metallic state. As regards the first two waves, the former wave represents the reduction of the original chromium(III) complexes to chromium(II) state and the latter represents the reduction of the aquated chromium(III) complexes to chromium(II) state. 3. In agreement with the result...
Calculation of Complex Radiant Heat Load From Surrounding Radiator Surface Temperatures
Abstract A method for calculating the radiant heat exchange between an absorber and individual radiating components in its surroundings is reported. Radiator surface temperatures, ambient and absorber temperatures, and configuration factors for radiating components in the surroundings are used in the customary radiant heat exchange formulae. Simplified methods for calculating or estimating configuration factors for radiators of various shapes solely from angles, subtended at the absorber by the radiators are presented. The method has been verified in the laboratory under controlled conditions and has been used to advantage in the field studies. The method has advantages over the globe therometer method in certain applications.