Visman equations in the design of sampling plans for chemical analysis of segregated bulk materials

Abstract

From preliminary measurements, guidelines are given for determining whether a bulk population is well-mixed or segregated and for the design of experiments to estimate sample size and number. For well-mixed populations, the total amount of sample collected determines the degree to which the population is represented. For segregated populations, sampling uncertainty is reduced primarily by increasing the number of sample increments collected. Methods for estimating Visman's sampling constants for segregated populations are discussed, along with a way of calculating a theoretical average particle mass for nonparticulate materials. An average theoretical particle mass of 20 g was calculated for unmixed samples of Athabasca oil sand. This large value, confirmed by using the Benedetti-Pichler equation, explains the extensive sampling required to estimate reliably the bitumen and water in oil sand.