Mass of Individual Samples Required

Many theories deal with the determination of the required mass of a sample from a heterogeneous bulk. Some of the most important of these must, furthermore, be discussed briefly. The dependence of sampling error on the grain size was discussed by REED [1881/82 1884/85] over 100 years ago. 

The question about the mass of sample required, which first appeared in the mining industry and which is widely accepted and also applicable to many environmental problems, is described by TAGGART s nomogram (Fig. 4-2). The dependence of the required total sample mass on the heterogeneity of the material and the concentration of the analyte are also discussed. 

A common and exact theory of sampling of inhomogeneous materials with stochastic composition is presented by BRANDS [1983]. Because experimental evaluation of this theory involves some difficulties, it was verified by simulation experiments. 

The shape factor,fshape, is the ratio of the average volume of all particles with a maximum linear dimension equal to the applied mesh size of a sieve to that of the cubes which will just pass the same sieve. The value offshape can be assumed to be 0.5 for the most materials. The particle size distribution factor, fsize distribution is the ratio of the upper size limit to the lower size limit. The composition factor, fcomposmon, is defined as  

An algorithm for the evaluation of the fundamental sampling error in the sampling of particulate solids, based on GY s theory, is described by MINKINNEN [1987]. 

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