A Text-book of Paper-making

by C. F. Cross; E. J. Bevan

• Water.
  • Hydrolysis, aided by acids formed from the wood. (Fry, 1867)
  • Limit of action de­ter­mined by re­ver­sal of hyd­rol­y­sis, i.e. de­hyd­ra­tion aid­ed by ox­i­da­tion.
• Water, together with neutral Sulphites.
  • Simple hydrolysis—
    • Products removed from sphere of ac­tion by comb­i­na­tion with base and sul­phite. (Cross, 1880.)
    • Oxidation prevented by presence of sulphite.

• Aqueous Acids.
  • (a) Oxidising and hydrolytic—
    • Nitric acid. (Coupier and Mellier, 1852. Barre and Blondel, 1861.)
    • Nitro-hyd­ro­chloric. (Orioli, 1865.)
  • (b) Simp­ly hydrolytic—
    • Hydro­chlor­ic acid. (Bachet and Machard, 1864.)
  • (c) Reducing and hydrolytic—
    • Sulphurous acid. (Tilghmann, 1866. Pictet, 1882.)
• Bisulphites.
  • Hydrolysis, aided primarily by sul­phur­ous acid, and sec­ond­ar­i­ly by com­bi­na­tion of prod­ucts with bi­sul­phites, also by pre­ven­tion of ox­i­da­tion. (Tilgh­mann, 1866. Mitscher­lich, 1874. Ekman, 1881. Francke, 1881. Graham, 1882.)

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CHAPTER VI. SPECIAL TREATMENT OF VARIOUS FIBRES; BOILERS, BOILING PROCESSES, ETC.

We have already, in Chapter V., discussed in a general way the principles upon which the treatment of the various fibres should be based; we now proceed to consider each fibre in detail, giving at the same time such information as is necessary regarding the preliminary treatment of the various fibres and describing the forms of apparatus in which these operations are conducted. We shall consider the fibres in the order of their simplicity of treatment.

Rags

The two former consist of the cuttings produced in the manufacture of various garments, &c.; not having been worn, they are usually free from dirt, and are, in fact, if bleached, nearly pure cellulose, containing only the starch and other sizing material which has been added in the process of finishing the goods. They may, of course, contain considerable quantities of china clay or other loading material. In purchasing rags, therefore, regard should be had to the probable presence of these bodies. Such rags require only a very slight treatment; in fact, for certain classes of paper they might be used without any preparation. If, as is sometimes the case, the rags are unbleached, a rather more severe boiling is necessary. {80}

FIG. 16.

The greater part of the rags used in paper-making, however, consist of the residual portions of garments, household linen, &c., which vary in quality from clean, almost unused portions, to the very foulest sorts; the latter require a very drastic treatment. The first thing to be done with the rags is to “sort” and cut them into convenient pieces. This is usually done by women, who stand at tables furnished with broad knives firmly fixed into them, with the backs towards the worker, and inclined at a slight angle. Near to the women are placed a number of boxes, corresponding with the number of qualities of rags, lined at the bottom with coarse wire gauze, into which the different sorts are put. The distinctions made are purely arbitrary, but as a general rule the rags are sorted with special reference to their colour and the material of which they are composed. The coloured rags may be allowed to accumulate, and then made into a coloured paper. During the process of cutting, all hard substances, {81} such as buttons, pieces of iron, &c., are carefully removed. The rags are cut into pieces of from two to five inches square. In some mills machines are used for cutting.