The sampling of the material that is to be analyzed is almost always a matter of importance, and not
infrequently it is a more important operation than the analysis itself. The object is to get a representative
sample for the determination that is to be made. This is not the place to enter into a discussion
on the selection of the bulk sample from its original site, be it quarry, rock face, stockpile, production
line, and so on. This problem has been outlined elsewhere.1–5 In practice, one of the prime factors that
tends to govern the bulk sampling method used is that of cost. It cannot be too strongly stressed that
a determination is only as good as the sample preparation that precedes it. The gross sample of the lot
being analyzed is supposed to be a miniature replica in composition and in particle-size distribution.
If it does not truly represent the entire lot, all further work to reduce it to a suitable laboratory size
and all laboratory procedures are a waste of time. The methods of sampling must necessarily vary
considerably and are of all degrees of complexity.
No perfectly general treatment of the theory of sampling is possible. The technique of sampling
varies according to the substance being analyzed and its physical characteristics. The methods of
sampling commercially important materials are generally very well prescribed by various societies interested
in the particular material involved, in particular, the factual material in the multivolume publications
of the American Society for Testing Materials, now known simply as ASTM, its former acronym.
These procedures are the result of extensive experience and exhaustive tests and are generally so definite
as to leave little to individual judgment. Lacking a known method, the analyst can do pretty well by
keeping in mind the general principles and the chief sources of trouble, as discussed subsequently.
If moisture in the original material is to be determined, a separate sample must usually be taken.
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