A morphological study is made of barium sulfate particles precipitated
from a homogeneous solution at 25° and 50° C in the presence
of various foreign substances and without them. As foreign
substances several types of compounds were chosen: a nonionic
detergent (Triton X-100), an anionic detergent (Aerosol MA), and
complexing agents (citrate and EDTA). The particles were studied
by electron microscopy. In all cases anisotropic particles were formed
with more or less defined structures, and most of the systems
were monodisperse. The appearance of twins, grown together in
different profile planes, was observed. The aging of particles in
mother liquor was studied, as well as the dissolution of particles
in water. On the basis of particle slize data, the morphological characteristics of particles, and their aging and dissolution, the mechanisms of particle foTmation were discussed. The -i!nfluence of foreign substances is discussed in terms of their chemical properties. lt lis sugges,ted that particles of barium sulfate are predominantly formed
by aggregation of primary particles, whilst pure diffusion growth is
encountered only under restricted conditions
