Photoconductivity of polystyrene doped with anthracene as a donor and 7,7,8,8-tetracyanoquinodimethane as acceptor was investigated by studying the photocurrent (I_ph), the dark current (I_d) and the sensitivityI_ph/I_d as the acceptor concentration changed. For this purpose a novel liquid cell was designed and successfully used for measurements. It was found that polystyrene films containing (1∶10) donor-to-acceptor ratio has the greatest sensitivity as the applied charging voltage equals 0·25 volt.

The thermal transformation of goethite to hematite and the temperature dependence of the degree of crystallinity have been investigated using transmission and diffraction electron microscopy and infrared spectroscopy.

The electron microscopy results reveal that the treatment of natural goethite by NaOH or citrate dithionite-bicarbonate (CDB) has no effect on its structure but leads to increase in the crystallinity of the ore. On the other hand, heat treatment of the untreated or treated sample is found to convert goethite ore to hematite with increase in its crystallinity. An infrared spectroscopic technique is applied for quantitative calculation of the crystallinity changes.