Dragons in Pursuit of the EBQ

Some of the objections to the classical model used in the theory of batch quantities are reviewed. They fall broadly into four categories (1) the validity of the model; (2) the determination of cost parameters; (3) criteria; (4) implementation. Some of the objections can be met by minor modifications of the model; others are more fundamental in nature. In multi-product situations the classical model can only provide an initial guidance and must be supplemented be other tools.     

Some aspects of discreteness-of-charge and ion-size effects for ions adsorbed at charged metal/aqueous electrolyte interfaces

It is argued that the self-image potential of an ion adsorbed on a charged metal from an aqueous electrolyte is described in terms of multiple imaging and not single imaging in the metal as proposed by Bockris. The image potential of an isolated ion situated on the i.H.p. in the inner region with a continuously and smoothly varying dielectric profile is calculated. This is compared with the corresponding potential for an inner region model with a discontinuous dielectric profile. It is shown that when the position of the i.H.p. relative to the o.H.p. is changed, the two potentials will in general cross each other such that the discontinuous model has the more negative self-image potential when the i.H.p. approaches the o.H.p. The scaled-particle expression for the entropic contribution due to ion-size effects in the adsorption isotherm of an ion in the inner region is compared with the corresponding Flory-Huggins formula. It is demonstrated that the two theories can give very different results. In particular, when the adsorbed ions are considerably larger than the solvent molecules, it is possible that scaled-particle theory leads to a ‘negative’ ion-size entropy term, which decreases with increase in density of adsorbed ion.     

Microdetermination of heavy metal ions: A potentiometric method using thioacetamide and iodine

Summary A new potentiometric method for the determination of mg range of silver, cadmium and copper ions is described. The heavy metal ions are first precipitated from an ammoniacal solution by an excess of thioacetamide. The precipitate is then separated by filtration. The unused thioacetamide is adjusted to the proper p_H and temperature, and then titrated with a standard solution of iodine potentiometrically. It is assumed that other metal ions, which form ammine complexes, can also be analyzed by this new method.

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Zusammenfassung Ein neues potentiometrisches Verfahren zur Bestimmung von Milligramm Ag, Cd und Cu wurde beschrieben. Die Schwermetallionen werden zunächst aus ammoniakalischer Lösung mit überschüssigem Thioacetamid gefällt. Der Niederschlag wird abfiltriert. Der überschuß an Thioacetamid wird nach Einstellung des p_H und der Temperatur mit einer Jodstandardlösung potentiometrisch zurücktitriert. Es ist anzunehmen, daß auch andere Metallionen, die Amminkomplexe bilden, so bestimmt werden können.