Clay chemical analysis
The
greatest care must be given in taking samples of clay for examination or chemical analysis.
A
carelessly taken sample is absolutely worthless for even a preliminary test.
In
preparing a sample of clay for chemical analysis, it is important to bear in
mind what constituents, separable by mechanical means, the clay contains. In which the industry it is likely to be used.To
reject, by a suitable treatment, from the analytical sample, those constituents
that will not enter into the ultimate product, though it is, of course,
necessary to at least approximately
determine their character and amount, as
this determines the future mechanical purification process to which such a
clay, if used, would have to be subjected.
Thus "lime-dogs" and pebbles are
objectionable in terra-cotta, brick and red ware clays, and are customarily
removed, if present, by screening the dried and crushed clay through a sieve of
ten to twenty meshes to the inch. Coarse sand and particles of iron-pyrites are
objectionable in finer terra-cotta, floor tile and yellow ware, and are removed
by disintegrating the clay in water, passing the "slip" through a
sieve of sixty meshes to the inch, and drying the purified clay. It may seem
superfluous to say that the chemical analysis of clay should be as accurate as
possible, while it is true that the chemical analysis alone, however accurate,
is insufficient without accompanying physical tests, to give one a perfect
characterization of a clay, its value is sufficiently great to warrant the most
careful work.
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