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 A TEXT-BOOK OF PAPER-MAKING;
 BY C. F. CROSS AND E. J. BEVAN (1888)




 [Illustration:

 COTTON. × 50.

 LINEN. × 50.

 ESPARTO. × 50.

 MECHANICAL WOOD-PULP. × 50.

 CHEMICAL WOOD-PULP. × 50.]




 A
 TEXT-BOOK OF
 PAPER-MAKING.

 BY
 C. F. CROSS AND E. J. BEVAN.

 [Illustration]

 E. & F. N. SPON, 125, STRAND, LONDON.
 NEW YORK: 35, MURRAY STREET.
 1888.




PREFACE.


The practical portion of the present work has in part already appeared
as an article, by one of the authors, in ‘Spons’ Encyclopædia of the
Industrial Arts.’ Since its publication, however, many and important
improvements have been introduced in this, as in other branches of
the art of paper-making, which necessitated considerable additions to
the original article. It has at the same time been to a great extent
re-written, and, as the authors hope, improved.

Our object in writing this book has been to bring before students and
others the principles upon which scientific paper-making should be
conducted, a concise exposition of which has not, we believe, been
hitherto attempted.

Considerable prominence has been given to this aspect of the subject,
possibly at the expense of what some may consider more essential
details.

A belief in the importance of a thorough scientific training for
paper-makers has dictated the style and purpose of the book.

We have not thought it necessary to enter into minute details
respecting the construction of machinery, &c.; for these the reader
is referred to such works as Hofmann’s Treatise on the Manufacture of
Paper.

Much of the scientific portion is here published for the first time.
Part of it has already appeared in the form of papers read before
various societies.

The chapter relating to the Treatment of Wood formed the subject of an
essay, which obtained the prize offered by the Scottish Paper-makers’
Association, in connection with the Edinburgh Forestry Exhibition, 1884.

We would here express our obligations to Messrs. G. and W. Bertram,
Messrs. Masson, Scott, and Bertram, Messrs. Rœckner and Co., and
others, for their courtesy in furnishing us with the drawings from
which the illustrations were prepared; to Dr. C. R. A. Wright, F.R.S.,
who kindly communicated the substance of the chapter on the Action of
Cuprammonium on Cellulose; to Mr. Carl Christensen, for drawings and
information regarding the manufacture of mechanical wood-pulp; also
to the following friends, among others, who have, in various ways,
rendered us important assistance:—Messrs. R. C. Menzies, C. M. King, G.
E. Davis, A. Beckwith, and C. Beadle.

Finally, we would tender our thanks to Mr. C. G. Warnford Lock for the
care he has bestowed on the editing of the book. The indexing and the
Chapter on Statistics are entirely his production.

  C. F. CROSS and E. J. BEVAN.

  4, NEW COURT, LINCOLN’S-INN, W.C.



  CONTENTS.


  INTRODUCTORY NOTE. . . 1


  CHAPTER I.

  CELLULOSE—THE CHEMICAL PROPERTIES OF TYPICAL MEMBERS OF
     THE CELLULOSE GROUP, WITH REFERENCE TO THEIR NATURAL
     HISTORY. . . 4


  CHAPTER II.

  PHYSICAL STRUCTURE OF FIBRES—MICROSCOPICAL EXAMINATION
    . . . 30


  CHAPTER III.

  CHEMICAL ANALYSIS OF PLANT SUBSTANCES. . . 42


  CHAPTER IV.

  AN ACCOUNT OF THE CHEMICAL AND PHYSICAL CHARACTERISTICS
     OF THE PRINCIPAL RAW MATERIALS. . . 46


  CHAPTER V.

  PROCESSES FOR ISOLATING CELLULOSE FROM PLANT SUBSTANCES
    . . . 62


  CHAPTER VI.

  SPECIAL TREATMENT OF VARIOUS FIBRES—BOILERS, BOILING
     PROCESSES, &C.. . . 79


  CHAPTER VII.

  BLEACHING. . . 110


  CHAPTER VIII.

  BEATING. . . 117


  CHAPTER IX.

  LOADING, SIZING, COLOURING, &C.. . . 127


  CHAPTER X.

  PAPER MACHINES, HAND-MADE PAPER. . . 144


  CHAPTER XI.

  CALENDERING, CUTTING, &C.. . . 167


  CHAPTER XII.

  CAUSTIC SODA, RECOVERED SODA, &C.. . . 177


  CHAPTER XIII.

  THE TESTING OF PAPER, MECHANICAL, CHEMICAL, AND
     MICROSCOPICAL. . . 193


  CHAPTER XIV.

  GENERAL CHEMICAL ANALYSIS FOR PAPER-MAKERS. . . 205


  CHAPTER XV.

  SITE FOR PAPER-MILL—WATER PURIFICATION. . . 210


  CHAPTER XVI.

  ACTION OF CUPRAMMONIUM ON CELLULOSE—WILLESDEN PAPER
    . . . 217


  CHAPTER XVII.

  STATISTICS. . . 221


  CHAPTER XVIII.

  BIBLIOGRAPHY. . . 229


  CHAPTER XIX.

  ADDENDA. . . 231


  INDEX. . . 233

{1}




PAPER-MAKING.

INTRODUCTORY NOTE.


The raw materials of the paper-maker are primarily the vegetable
fibrous substances; in addition to these there are various articles
which are employed as auxiliaries, either in the preparatory or
finishing processes to which these fibrous materials, or the web of
paper are subjected. The latter class are of subsidiary importance,
more especially from our present point of view.

In insisting upon the recognition of first principles, we cannot
overrate the importance of a thorough grasp of the constitution of the
plant fibres, as the necessary foundation for the intelligent conduct
of paper-making, and to this subject we will at once proceed.

Careful study of a mature plant will show that it is made up of
structural elements of two kinds, viz. fibres and cells, which, to use
a rough parallel, we may liken in function to the bricks and mortar
of a house. It is the former which admit of the many extended uses,
with which we are familiar, in the arts of spinning and weaving, and
which constitute the fabrics which are the most indispensable to our
civilised life. For the most part, as we know, fibres and cells are
aggregated together into compound tissues, and a process of separation
is therefore a necessary preliminary to the utilisation of the former.
The cotton fibre is the only important exception to this general
condition of distribution. Here we have the seed envelope or perisperm,
converted into a mass {2} of fibres, and these by a spontaneous
process accompanying the ripening, so isolated as to be immediately
available. Next in order in point of simplicity of isolation, are those
fibrous masses, or tissues, which, although components of complex
structures, exhibit a greater cohesion of their constituent fibres than
adhesion to the contiguous cellular tissues with which they go to build
up the plant. Into such a tissue the “bast,” or inner bark layer of
shrubs and trees, more especially those of tropical and sub-tropical
regions, frequently develops, and it is, in fact, this bast tissue,
graduating in respect of cohesion of its constituent fibres, from a
close network such as we have spoken of, to a collection of individual
fibres or fibre-bundles disposed in parallel series, which supplies
the greater part of the more valuable of the textile and paper-making
fibres; we may instance flax, hemp, and jute, each of which is the
basis of an enormous industry. According to the degree of adhesion of
the bast to the contiguous tissues, or, in another aspect, according to
its lesser aggregate development, so is the difficulty of isolation and
the necessity of using processes auxiliary to the mechanical separation
of the tissue.

It is worthy of note here that the Japanese paper with which we
are in these times so familiar, is prepared by the most primitive
means from the bast of a mulberry (_Broussonetia papyrifera_); the
isolated tissue, consisting of a close network of fibres, is simply
cut and hammered to produce a surface of the requisite evenness, and
the production of a web of paper is complete. In isolating the bast
fibres employed in the textile industries, a preliminary partial
disintegration of the plant stem is brought about by the process of
steeping or retting, by which the separation of fibre from flesh or
cellular tissue is much facilitated.

Last in order of simplicity of distribution, we have the fibres
known to the botanist as the fibro-vascular bundles of leaves and
monocotyledonous stems, these bundles being irregularly distributed
through the main cellular mass, and consequently, by reason of adhesion
thereto, much more {3} difficult of isolation. For this and other
reasons, more or less in correlation with natural function, we shall
find this class of raw material lowest in value to the paper-maker.

It is necessary at this stage to point out that the work of the
paper-maker and that of the textile manufacturer are complementary one
to the other, and the supply of fibrous raw material is correspondingly
divided: it may be said, indeed, that the paper industry subsists
upon the rejecta of the textile manufactures. The working up of
discontinuous fibre elements into thread, which is the purpose of the
complicated operations of the spinner, is conditioned by the length
and strength of these ultimate fibres. Paper-making, on the other
hand, requires that the raw material shall be previously reduced to
the condition of minute subdivision of the constituent fibres, and
therefore can avail itself of fibrous raw material altogether valueless
to the spinner, and of textile materials which from any cause have
become of no value as such. To the raw materials of the paper-maker,
which we have briefly outlined above, we must therefore add, as a
supplementary class, textiles of all kinds, such as rags, rope, and
thread.

Having thus acquired a general idea of the sources of our raw
materials, we must study more closely the substances themselves, and
first of all we must investigate them as we should any other chemical
substance, i.﻿e. we must get to understand the nature and properties
of the matter of which the vegetable fibres are composed. While these
exhibit certain variations, which are considerable, the substances
present a sufficient chemical uniformity to warrant their being
designated under a class name: this name is cellulose. The prototype of
the celluloses is the cotton fibre.

{4}




CHAPTER I.

CELLULOSE: THE CHEMICAL PROPERTIES OF TYPICAL MEMBERS OF THE CELLULOSE
GROUP, WITH REFERENCE TO THEIR NATURAL HISTORY.


Plants are so far built up of cellulose that it may be called the
material basis of the vegetable world. Plant tissues, however, seldom,
if ever, consist of pure cellulose, but contain besides, other products
of growth either chemically combined with the cellulose or mechanically
bound up with the tissue, which are, according to the nature of their
union, removable either by means of fundamental chemical resolution
or by the application of simple solvents. A general method for the
isolation of cellulose consists in exposing the moist tissue to
the action of chlorine gas or of bromine water in the cold, and
subsequently boiling in dilute ammonia; repeating this treatment until
the alkaline solution no longer dissolves anything from the tissue or
fibre. The cellulose is then washed with water, alcohol, and ether,
and dried. Obtained in this way, or in the form of bleached cotton, or
of Swedish filter paper, it is a white substance, more or less opaque,
retaining the microscopic features of the tissue or fibre from which it
has been isolated. Its sp. gr. is 1·25–1·45. Its elementary composition
is expressed by the percentage numbers (Schulze)

  C      44·0      44·2
  H       6·3       6·4
  O      49·7      49·4

or by the corresponding empirical formula, viz. C_{6}H_{10}O_{5}.

These numbers represent the composition of the ash-free cellulose.
Nearly all celluloses contain a certain proportion, {5} however small,
of mineral constituents, and the union of these with the organic
portion of the fibre or tissue is of such a nature that the ash left on
ignition preserves the form of the original. It is only in the growing
point of certain young shoots that the cellulose tissue is free from
mineral constituents. (Hofmeister.)

As already indicated, cellulose is insoluble in all simple solvents;
it is, however, dissolved by certain reagents, but only by virtue of a
preceding chemical modification. An exception to this is to be found,
perhaps, in the ammoniacal solution of cupric oxide (Schweitzer’s
reagent), in which it dissolves without essential modification, being
recovered by precipitation, in a form which is chemically identical
with the original, though differing, of course, in being structureless,
or amorphous. This reagent may be employed in a variety of forms, but
the following method of using it is to be recommended as the most
certain in its results. The substance to be operated upon is intimately
mixed with copper turnings in a tube which is narrowed below and
provided with a stopcock. Strong ammonia is poured upon the contents of
the tube and, after being allowed to stand for some minutes, is drawn
off and returned to the tube; the operation is several times repeated
until the solution of the substance is effected. In order to facilitate
the oxidation of the copper by the atmospheric oxygen, a current of
air may be aspirated through the apparatus. The solution of the oxide
prepared in this way is more effective in its action on cellulose
than that obtained by dissolving the precipitated hydrate in ammonia.
Cellulosic tissues in contact with this reagent are seen to undergo
a disaggregation of their fibres, which swell up, become gelatinous,
and disappear in solution. On adding an acid to the viscous solution,
a precipitate of the amorphous cellulose is obtained in the form of a
jelly resembling hydrated alumina; after washing and drying, it forms
a brownish, brittle, horny mass. The cellulose is also precipitated
upon simply diluting the viscous solution with water and allowing it
to stand {6} 8–10 days in a closed vessel. From this observation it
was inferred by Erdmann that the cellulose could not be considered
as dissolved in the strict sense of the word, but the experiments
of Cramer upon the osmotic properties of the solution proved this
inference to be unfounded, and that cellulose is actually dissolved by
the ammoniacal solution of copper oxide.

On treating the ammonio-cupric solution of cellulose with metallic
zinc, this metal precipitates the copper, replacing it in the solution,
and producing the corresponding ammonio-zincic solution of cellulose,
which is colourless. Some of these solutions are lævo-gyrate.

Cellulose, in those forms to which the application of the term has
been hitherto restricted, is a comparatively inert substance, and its
reactions are consequently few. One of these is available for the
identification of cellulose, and is chiefly used in the microscopical
examinations of tissues: this is its reaction with iodine. Cellulose
is not  blue by a solution of iodine excepting under the
simultaneous influence of hydriodic acid, potassium iodide, sulphuric
acid, phosphoric acid, or zinc iodide or chloride. The solution is
prepared in the following way: zinc is dissolved to saturation in
hydrochloric acid, and the solution is evaporated to sp. gr. 2·0; to
90 parts of this solution are added 6 parts potassium iodide dissolved
in 10 parts of water; and in this solution iodine is dissolved to
saturation. By this solution cellulose is  instantly a
deep-blue or violet. For the identification of cellulose in the gross,
mere inspection is usually sufficient; confirmatory evidence is
afforded by an observation of the action of the ammonio-copper reagent,
and of the absence of reaction with chlorine water. (See p. 18.)

Cellulose in its earlier stages of elaboration has no action upon
light; but with age it acquires the property of double refraction, not,
as has been shown by experiment, by virtue of its state of aggregation,
but of its molecular constitution (Sachs). {7}

_Animal Cellulose._—The mantles of many of the mollusca, e.g. the
_Pyrosomidæ_, _Salpidæ_, and _Phallusia mammillaris_, contain a
resistant substance which, after isolation by chemical treatment,
has been found to be identical both in composition and properties
with vegetable cellulose. Cellulose has also been stated to occur in
degenerated human spleen and in certain parts of the brain.

_Compounds of Cellulose._—The chemical inertness of cellulose is a
matter of everyday experience in the laboratory, where it fulfils
the important function of a filtering medium in the greater number
of separations of solids from liquids. Its combinations with acids
and with basic oxides are, as might be expected, few and of little
stability. It has been shown by Mills that cellulose (cotton) in
common with certain other organic fibrous substances, when immersed in
dilute solutions of the acids or basic oxides, condenses these bodies
within itself at the expense of the surrounding solution, which is
proportionately weakened. This effect of concentration is sufficiently
uniform and constant to lead us