Diffuse reflectrace technique for the measurement of forbidden energy gap, E,, is discussed. The energy coordinate of the point a t which the linear increase in the KubelkaMunk function starts gives the Eg-value. The E,-values of fifteen semiconductors are reported. These E,-values are found to be in good agreement with those measured by other methods.Es wird die Methode der diffusen Reflexion fur die Messung der Breite E, der verbotenen Zone diskutiert. Der Energiewert des Punktes, an dem der lineare Anstieg der KubelkaMunk-Funktion beginnt, ergibt den Eg-Wert. Die Eg-Werte fur funfzehn Halbleiter werden mitgeteilt. Diese Eg-Werte befinden sich mit denen, die mit anderen Methoden gemessen wurden, in guter ;obereinstimmung.

The paper embodies an analytical approach to the recovery of chromium and nickel from different kinds of industrial wastes, namely, a Cr(III)-Ni(II) plating sludge, a Ni(II) plating mug, and a tannery effluent. The proposed methods employ precipitation, solvent extraction, and electrowinning steps. A toluene solution of Cyanex 923 is used as an extractant for the separation of Cr(III) and Ni(II) from some commonly associated metal ions such as Al(III), Fe(III), Mn(II), Co(II), Cu(II), Zn(II), and Pb(II). The experiments conducted up to 10 cycles indicate a negligible loss in extraction efficiency. The electrodeposition of Cr(III) and Ni(II) offers average cathode efficiencies around 40 and 75%, respectively. The recovered metals are 99.9% pure. The proposed procedures will be helpful in saving the wastage of metals and protecting the environment from metal pollution.

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