The rapid technique of measuring overpotential leads t o the most reproducible results in acid solutions if the solutions are adequately purified. The negative deviations from the Tafel equation a t high c.d.'s are spurious and caused by impurities such as H,S (or a similar substance) in the electrolyte, which is adsorbed a t the electrode only a t potentials far from the electrocapillary maximum. The additions of O,, H,O,, As,O, have a qualitatively similar effect on the course of the potential-log c.d. relation. Equations are deduced for * Fig. 5 and 7 are taken from Parsons, Thesis (London, 1945).

An apparatus is described for the measurement of overpotential at very high current densities and the correction of the results for ohmic and concentration overpotential. The potential-distance relation within about 0-05 cm of the electrode surface is linear and undergoes a sharp inflection at distances greater than this. Measurements have been made 145

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Nanotechnology is one of the most emerging fields in the recent years. In the current investigation, we report the biosynthesis of iron nanoparticles (Fe-NPs) employing Alternaria alternata fungus, which is an eco-friendly process for the synthesis of metallic nanoparticles. Fe-NPs were synthesized through the reduction of aqueous Fe 3+ ion in the dark conditions. Ultraviolet-visible spectrum of the aqueous medium containing iron ion showed a peak at 238 nm and another peak at 265 nm. The forming of nanoparticles was confirmed by transmission electron microscope, scanning electron microscope and energy-dispersive x-ray. The morphology of nanoparticles is found to be cubic shapes mostly and the average particle diameter as determined by scanning electron microscope was found to be 9±3 nm. Fe-NPs showed antibacterial activity against both Gram-positive and Gram-negative bacteria used in this study due to its oxidative damage for bacterial cell wall. Iron nanoparticles show more antimicrobial activity to Bacillus subtilis than Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa.

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Strahlverdichtern und Trockenkondensierung ist aus Abb. 2 ersichtlich. Die Energievorteile des Verfahrens sind um so griiljer, je niedriger der Betriebsdruck ist, und machen sich besonders im Vakuumbereich unter 5 Tom bemerkbar. 3.2 3.0 28 26 2.L 2 2 LO 1.8 1.6 1.4 1.2 1.0 0.0 OE 0.1 0.; ""kg Stripping Shorn 2ODCleaCking Pressure IOoCIBocking Presswe 30Tcfrl 18Torr) l0OC 1 2 3 L 5 6 7 8 9 l O -b -r Abb. 2. Energieverbrauch bei der Trockenkondensierung und modemen Strahlverdichtem b) Beseitigung der Wasseruerschmu&ung Statt einer barometrischen Kiihlwassermenge von etwa 150 m3/h, leicht verschmutzt und oft unakzeptabel aussehend, entsteht jetzt eine Gesamt-Kondensatmenge von nur ca. 150 kg/h. Das Kondensat stellt eine instabile Emulsion d q die sich leicht in eine Wasser-und eine Fettsaure-Phase trennen 1iiBt. Die Fettsauren sind natiirlich in der Zusammensetzung leichter als die produzierten Fettsauren und haben hohere Anteile an Unverseifbarem und Geruchsstoffen. Die Fettsauren lassen sich getrennt aufarbeiten.h e gereinigte Wasserphase hat einen COD-Gehalt bis etwa 5000 mg/l und 1a;Bt sich ohne Schwierigkeiten biologisch reinigen. c) WasserbedarfDer Wasserbedarf l a t sich nach den ortlichen Verhaltnissen auf ein Minimum reduzieren, indem sich z. B. die NH3-Kondensatoren mit Verdampfungskiihler oder Luftkiihler ausstatten lassen.

The potential, which a silver wire acquires in contact with Ag+ ions in concentrated solutions of KCN, was studied potentiometrically. The solubility products or the instability constants of the following reactions have been calculated: Normal potential values corresponding to the preceding equilibria were evaluated as +0.136, −0.135, −0.407 and −0.498 V. respectively. The corresponding free enthalpy values were calculated as 20.69, 21.51, 27.76 and 29.86 kcal per mole. This could be looked upon as the first published inclusive data on the Ag(CN) 2−3 ion.

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