A previously published expression for estimating aggregation time is assess
ed by comparison with times calculated using a numerical, population-balanc
e aggregation model. Estimates of aggregation time calculated using the alg
ebraic expression underpredict model values. The relationship between the a
ggregation times estimated using the two methods is highly linear. An expre
ssion to directly relate the two estimates is derived. (C) 1999 Elsevier Sc
ience B.V. All rights reserved.