Tracer crystals are developed to study the agglomeration, growth and r
esidence time behavior of gibbsite crystals, an industrially important
polymorph of Al(OH)(3), in continuous and batch precipitation. Satisf
actory tracer crystals contain detectable amounts of Zn and have the c
rystal structure of gibbsite. The tracer crystals behave in the same m
anner during precipitation as the nontracer Al(OH)(3) crystals. The ap
plication of the tracer crystals for investigating, both batch and con
tinuous, seeded Al(OH)(3) precipitation is demonstrated. The tracer ex
periments provide information on the growth and agglomeration kinetics
of different size fractions. The tracers are a useful tool for the qu
antitative investigation of solid-phase residence time distributions w
ithin a crystallizer.