removing, sampling, and weighing for a yield determination. Tests have
shown that it is possible to sample and calculate the yield of bone-dry
fiber within 0.05 per cent of the actual amount.

It has been found that stocks from different materials vary greatly in
their ability to mat in the drain tank, thereby enabling a good vacuum
to be obtained, some stocks permitting a 25-inch vacuum to be obtained,
while others will not permit more than 5 inches. For this reason the
moisture content of the stock will vary from 65 to 85 per cent.

_Washing and bleaching._--Washing and bleaching were performed for the
purpose of bleaching the brown-colored cooked stock to a white product,
since it was regarded as highly probable that the fiber would be
suitable for book-paper manufacture. The colored stock was charged into
a 400-pound beating and washing engine of regular construction and
washed about one hour, the cylinder washer being covered with 60-mesh
wire cloth in order to remove fine loose dirt and chemical residues. The
washer was then raised, the stock heated by steam to about 40° C., and a
solution of commercial bleaching powder was added in the quantity judged
to be necessary, after which the stock was pumped to a large wooden
tank, to remain and bleach over night. If the stock was bleached
sufficiently white it was drained and washed from bleach residues, and
if not more bleach was added until a good color was obtained. The
bleaching powder used was estimated to contain 35 per cent of available
chlorin, as this is the commercial practice, and the amount required was
calculated to the bone-dry weight of the unbleached stock. More bleach
is required for undercooked stock than for stock which is properly
cooked or overcooked; therefore, the percentage of bleach required is an
indication of the quality of the cooked stock. Since bleaching is
usually more expensive than cooking, it is desirable to cook to such a