If a sample of pulp of considerable size be thrown on a folded filter,
a filtrate is obtained whose composition has a definite relation to
that of the whole pulp.
(_a_) _By drying._—The per cent of solids in the filtrate may be
determined by drying _in vacuo_ at 70° C, or under atmospheric pressure
at the temperature of boiling water.
As in the case of the drying of pulp, a constant relation is found
to exist between the per cent of solids in the filtered liquor as
determined by drying _in vacuo_ at 70° C., and the per cent of solids
as determined by drying at atmospheric pressure at the temperature
of boiling water. The per cent of solids in the filtrate obtained by
drying at atmospheric pressure, multiplied by 1.125, gives the per cent
of solids obtained by drying _in vacuo_. This relation is shown in
detail in Table 5.