K. C. SEN, S. C. RAY AND S. K. TALAPATRA 271
experiment thus showed that the combined residual liquor and the first wash
could be economically utilized for two more similar treatments after adjusting
the strength of the alkali by adding 50 per cent of the requisite quantity
of caustic soda. The above experiment, furthermore, showed that, under the
same environmental conditions, a mixture of 1.5 per cent sodium carbonate
solution and 1.25 per cent caustic soda in the proportion of 6 : 5, was as effec-
tive for treatment as 1.25 per cent caustic soda solution used alone.
Large-scale alkali treatment of straw
Following exactly the same method as that described for alkali treatment
of straws in the laboratory, a large-scale treatment of two kinds of straws, viz.
wheat and paddy, was carried out. Eighty pounds of straw were treated
every day in a round-bottomed trough made of galvanized iron sheeting with
angle iron support. The trough measured approximately 5 ft. x 3 ft. x 2½ ft.
At the bottom of one extremity of the trough was a small opening, which
could be plugged with a rubber stopper. At the time of treatment, the end
of the trough opposite to the opening was raised in order to provide a slight
incline. Every day a fresh solution of alkali was prepared by dissolving
approximately 4 kg. of commercial caustic soda in 64 gallons of water. A
weighed quantity (80 lb.) of finely chopped straw was added to the solutions
in eight lots. After each lot had been added, it was pressed into the solution
to facilitate soaking. When the whole of the straw had been thus soaked,
the mass was periodically turned over with iron rakes to allow uniform action
by the alkali. At the end of 20 to 24 hours, the treated straw was pulled up
to the raised end of the trough with a rake and the alkaline liquor allowed
to trickle down to the lower end of the trough. The rubber plug fitted to
the opening was removed to permit the liquor to run out. Thereafter, the
plug was again inserted and half the volume of water originally used for soak-
ing was added to the trough. The alkali-treated straw was thoroughly turned
over in this fresh water to wash out the alkali.. As before, the mass of
straw was pulled up to the raised end and the wash water allowed to run out
of the trough through the hole. Two more similar washings were carried out
with the same volume of fresh water. Altogether, for treating one batch of
80 lb. of straw, about 160 gallons of water were used. The treated straw
after the third washing was thoroughly squeezed to remove the water and was
then spread out in the sun to dry. In ordinary dry summer months, perfect
drying (90 to 95 per cent dry matter) can be achieved when the straw is spread
out in the sun for two consecutive days. On wet days, drying was carried
out indoors by spreading the straw thinly over the floor and frequently stirring
it with a rake. The treated straw dried up to 85 to 90 per cent dry matter
within four to five days. During the drying process no deterioration of any
kind was noticed. Altogether, 20 lots of 80 lb. of straw of both kinds, were
treated. In this large-scale treatment, 76 and 72 per cent dry matter were
recovered for wheat and paddy straw respectively. The composition of the
treated straws are shown in Tables X to XXI. A perusal of the data will
show that the composition of the large-scale treated straw compares very
favourably with that of the same straws treated in the laboratory (Tables II
and V). The treated straws were subsequently used for feeding trials and
metabolism experiments with Sahiwal heifers.