Page:Zacaton as a paper-making material (IA zacatonaspaperma309bran).pdf/18

 BULLETIN

12

309.

U.

S.

DEPARTMENT OF AGRICULTURE.

by acid hydrolysis; the caustic-soda hydrolysis with caustic soda; and the sulphate process, hydrolysis with sodium hydrate and sulphid.

grinding; the sulphite process, process,

by

by

From previous general knowledge of the paper value of fibrous plants and from the similarity of zacaton to known species, it was decided to investigate this material by the soda process, which consists in

subjecting the material to the action of a caustic-soda solution

at moderately high temperature for a definite length of time,

operation

is

technically

known

as cooking.

which

Since the soda solutions

at the temperatures required exert a steam pressure of 50 to 100 pounds to the square inch, the cooking is effected in large, strong steel cylinders, known as digesters, which are of two general types, the upright stationary and the horizontal rotating. The prehminary cooking of zacaton was conducted in an autoclave, simulating the conditions of the upright stationary digester. The autoclave was of the regular laboratory type, of 7J-liter capacity, composed of a rigid stand supporting the spun-copper autoclave shell, which could be securely closed by clamping on a bronze head or cover, the seal being secured by polished surfaces between the body and the head. The head was provided with a pressure gauge and thermometer well. A gas burner underneath the shell served to heat the charge to any

desired temperature or pressure.

The method hi the body,

of operation

is

to place a certain weight of material

to cover with a soda solution containing sufficient

caustic soda to completely reduce the material, to securely close the

by means

heat the entire charge This pressure is maintained the required number of hours, after which the charge is allowed to cool and the contents are removed and washed free from the dark-, colored spent soda solution known as black liquor. Undercooked pieces of grass, which are invariably present, are separated from the pulp by screening through a No. 10 screen, in which the slots are autoclave, and,

of the gas burner, to

to a definite temperature or pressure.

an inch wide. material under examination contains pith cells which by reason of their high percentage or quality tend to impart undesirable qualities to the finished sheet, it will be necessary to separate them from the true fiber at this point. Separation can readily be accomplished by manipulating the pulp on a 60 or 70 mesh wire cloth with a stream of water, whereby the small pith cells are washed away, In the case of zacaton it leaving the long, true fibers on the wire. does not appear necessary or advisable to separate the pith, and it was done only in cook No. 1. In autoclave cook No. 1, 404 grams of grass, bone-dry basis, were treated with 24.4 per cent of caustic soda at a concentration of 19.7 0.01 of

If the