On the Effects of Particle Size and Shape on the Colour of Ferric Oxide powders

Ferric oxide powders prepared by calcining iron salts exhibit a variety of colours, i. e. pure red, yellowish red, dark red, and black, according to the condition of calcination. Morphological studies revealed that the colour of powders is dependent upon the size and shape of the unit particles and their aggregates. The powders change in colour from yellowish red or dark red to black as the size of unit particles or of their aggregates increases. On the basis of this result explanations were given to the nature of colour of glaze containing iron red and, also, of water containing Fe2O3 in colloidal subdivision.