By M.H. TAUSS.
The researches of the author upon the action which water exerts upon
wood at a high temperature have shown how much of the incrusting
material can be removed without the aid of any reagent.
In connection with the manufacture of cellulose, it is also
interesting to prosecute at the same time experiments with solutions
of the caustic alkalies, in order to study the mode of action upon
both wood and pure cellulose. The manufacture of cellulose has for
many years been an industry, and yet little or nothing from a chemical
point of view is known of the action of caustic soda upon vegetable
fibers.
Braconnot, in 1820, obtained alumina by treating wood with an alkali,
but the first application of wood to the manufacture of paper was due
to Chauchard. By boiling vegetable fibers with caustic lyes, Collier
and Piette obtained cellulose. Again, in 1862, Barne and Blondel
proposed to make cellulose in a similar way, but employed nitric acid
in the place of soda.
The first cellulose made exclusively from wood and caustic soda was
produced at the Manayunk Wood Pulp Works, in 1854, in the neighborhood
of Philadelphia, by Burgess & Watt. The operation consisted in
treating the wood for six hours at a pressure of from six to eight
atmospheres, with a solution of caustic soda of 12° B.
Ungerer noticed that it was sufficient to limit the pressure from
three to six atmospheres, according to the quality of the wood, and
advised the use of solutions containing four to five per cent. of
caustic soda. He employed a series of cylinders, arranged vertically,
in which the wood was subjected to a methodical system of lixiviation.
The same lye passed through many cylinders, so that when it made its
exit at the end it was thoroughly exhausted, and the wood thus kept
coming in contact with fresh alkaline solutions.
According to the account of Kiclaner, the disintegration of wood may
be effected in the following four ways:
1. By heating direct in boilers at a pressure of 10
atmospheres. (See Dresel and Rosehain.)
2. In vertical boilers heated direct or by steam, and kept at
a pressure of from 10 to 14 atmospheres. (Sinclair, Nicol, and
Behrend.)
3. In revolving boilers, maintained at a pressure of 12
atmospheres by direct steam.
4. By means of a series of small vessels communicating with
each other, and through which a lye circulates at a pressure
of six atmospheres. (Ungerer.)
This latter process is preferable to the others.
Researches have also been made by the author in order to ascertain the
loss which wood and cellulose suffer at different temperatures or in
contact with varying quantities of alkali (NaHO).
The following is a _resumé_ of the experiments, giving the loss in per
cent. resulting from a "cooking" of three hours duration:
I. Ordinary pressure:
10 grms. cellulose, with 580 c.c. of caustic
soda solution, sp. gr. 1.09 21.99
10 grms. of soft wood, treated as above 49.19
10 " hard " " " 53.68
II. Pressure of five atmospheres:
10 grms. cellulose, with 500 c.c. caustic soda
solution of sp. gr. 1.099 58.02
10 grms. of soft wood, treated as above 75.85
10 " hard " " " 69.80
III. Pressure of ten atmospheres:
10 grms. of cellulose 58.99
10 " soft wood 81.80
10 " hard " 70.39
IV. Ordinary pressure:
10 grms. of cellulose, with 500 c.c. caustic
soda solution of sp. gr. 1.162 21.88
10 grms. of soft wood 35.45
10 " hard " 46.43
V. Pressure of five atmospheres:
10 grms. of cellulose, with 500 c.c. caustic
soda solution of sp. gr. 1.162 77.33
10 grms. of soft wood 97.13
10 " hard " 91.48
VI. Ordinary pressure:
10 grms. of cellulose, with 500 c.c. caustic
soda solution of sp. gr. 1.043 12.07
10 grms. of soft wood 28.37
10 " hard " 30.25
VII. Pressure of five atmospheres:
10 grms. of cellulose, with 500 c.c. of caustic
soda solution of sp. gr. 1.043 15.36
10 grms. of soft wood 50.96
10 " hard " 55.66
VIII. Pressure of ten atmospheres:
10 grms. of cellulose, with 200 c.c. caustic
soda solution of sp. gr. 1.043 20.28
10 grms. of soft wood 70.31
10 " hard " 65.59
From this it is evident that by increasing the temperature and
pressure the solvent action of the alkali is increased, but the
strength of the lye exercises an influence which is even more marked.
Thus, at a pressure of five atmospheres, the loss of cellulose was
0.75 with a caustic lye containing 14 per cent. of NaHO, while it was
only 0.05 with a lye of 8 per cent. NaHO.
To further elucidate the action of the alkali under the conditions
given above, the author has estimated the amount of precipitate which
alcohol gives with the soda solutions, after boiling with the wood:
1. 2. 3.
Specific gravity of NaHO solutions 1.043 1.09 1.162
Soft wood, ordinary pressure 1.043 traces 4.8
" pressure of five atmospheres 1.043 2.0 26.8
" " ten " 1.043 1.7 --
Hard wood, ordinary pressure 11.10 27.40 30.80
" pressure of five atmospheres 1.10 25.70 15.8
" " ten " traces 5.20 15.8
The estimation of the precipitate, produced in the soda solutions
employed in the experiments cited above, gives:
Soft wood, ordinary pressure 1.31 traces 2.0
" pressure of five atmospheres 15.94 16.0 24.80
" " ten " 17.00 25.4 --
Hard wood, ordinary pressure 5.40 6 5.60
" pressure of five atmospheres 9.40 15.40 33.60
" " ten " 14.00 18.40 33.60
As a general rule manufacturers employ a greater pressure than that
which was found necessary by the author. As a result, it appears from
these experiments that the wood not only loses incrusting matter, but
that part of the cellulose enters into solution. As a matter of fact,
the yield obtained in practical working from 100 parts of wood does
not exceed 30 to 35 per cent.--_Le Bull. Fab. Pap.; Chemical Trade
Journal._
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