For anthracite, coke, and coal of high ash content, that do
no readily burn completely, one of the following procedures are
recommended: (1) The inside of the sample holder is lined completely
with ignited asbestos in a thin layer pressed well down in the angles, and
the sample is then sprinkled evenly over the surface of the asbestos.
(2) The mass of the sample may be varied to obtain good ignition. lfthe
mass is varied, it will be necessary to recalibrate the calorimeter so that
the water equivalent will be based on the same temperature rise as that
obtained with the sample weight. (3) A known amount of benzoic acid
may be mixed with the sample. Proper allowance must be made for the
heat of combustion of benzoic acid when determining the calorific value
of the sample