2 EXPERIMENTAL PROCEDURE

THE FIRST GROUP of pigments to undergo analysis were the whites. These were generally in the form of a dry powdered pigment of ground-up mineral. All but one were inorganic in nature and thus suitable for study using x-ray diffraction (XRD). To assist in the interpretation of the x-ray diffraction pattern data, energy dispersive x-ray flourescence (XRF) was used to study the elemental composition of some samples.

X-ray powder diffraction patterns of pigment samples were produced using Debye-Scherrer and Gandolfi (114.6 cm) cameras mounted on a Philips Model 12045 XRD generator. Copper Kα radiation, a potential of 30KV and 15 mA of current were used. The spacings and relative intensities were read off the film (Kodak: No-Screen film, NS-392T); the d-values were calculated from the data and compared to known values taken from the JCPDS Powder Data file1–5

X-ray fluorescence results were obtained using a Kevex Model 0750 system, which uses an energy dispersive solid state detector with excitation from a Rh anode x-ray tube using a variety of secondary targets.