For lots of
less than ten drums, unless there is reason to suspect want of
uniformity, it should usually suffice to draw the sample from one drum
selected at random by the sampler. The analyst, or person who undertakes
the sampling, must, however, exercise discretion as to the scheme of
sampling to be followed, especially if want of uniformity of the several
lots constituting the consignment in suspected. The size of the lumps
constituting a sample will be referred to later.
The British Association's regulations lead to a sample weighing about 3
lb. being obtained from each drum. If only one drum is sampled, the
quantity taken from each position may be increased with advantage so as
to give a sample weighing about 10 lb., while if a large number of drums
is sampled, the several samples should be well mixed, and the ordinary
method of quartering and re-mixing followed until a representative
portion weighing about 10 lb. remains.
A sample representative of the bulk of the consignment having been
obtained, and hermetically sealed, the procedure of testing by means of
the apparatus already described may be given from the German
Association's directions:
"The first carbide receptacle is filled with 300 to 400 grammes (say 3/4
lb.
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