SECTION I. GENERAL CHEMISTRY OF THE TYPICAL COTTON CELLULOSE_Researches on Cellulose, 1895-1900

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RESEARCHES ON CELLULOSE

1895-1900

CROSS & BEVAN

(C. F. CROSS AND E. J. BEVAN)

_SECOND EDITION_

LONGMANS, GREEN, AND CO.

39 PATERNOSTER ROW, LONDON

NEW YORK, BOMBAY, AND CALCUTTA

1907

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Transcriber's note:

For Text: A word surrounded by a cedilla such as ~this~ signifies that

the word is bolded in the text. A word surrounded by underscores like

_this_ signifies the word is italics in the text. The italic and bold

markup for single italized letters (such as variables in equations) and

"foreign" abbreviations are deleted for easier reading.

For numbers and equations: Parentheses have been added to clarify

fractions. Underscores before bracketed numbers in equations denote a

subscript. Superscripts are designated with a caret and brackets, e.g.

11.1^{3} is 11.1 to the third power. Greek letters in equations are

translated to their English version.

The sections in the Table of Contents are not used in the actual text.

They have been added for clarity.

Minor typos have been corrected and footnotes moved to the end of the

sections

* * * * *

PREFACE TO SECOND EDITION

This edition is a _reprint_ of the first in response to a continuous

demand for the book. The matter, consisting as it does largely of

records, does not call for any revision, and, as a contribution to the

development of theory, any particular interest which it has is

associated with the date at which it was written.

The volume which has since appeared is the sequel, and aims at an

exposition of the subject "to date".

PREFACE

This volume, which is intended as a supplement to the work which we

published in 1895, gives a brief account of researches which have been

subsequently published, as well as of certain of our own investigations,

the results of which are now for the first time recorded.

We have not attempted to give the subject-matter the form of a connected

record. The contributions to the study of 'Cellulose' which are noticed

are spread over a large area, are mostly 'sectional' in their aim, and

the only cohesion which we can give them is that of classifying them

according to the plan of our original work. Their subject-matter is

reproduced in the form of a _precis_, as much condensed as possible; of

the more important papers the original title is given. In all cases we

have endeavoured to reproduce the Author's main conclusions, and in most

cases without comment or criticism.

Specialists will note that the basis of investigation is still in a

great measure empirical; and of this the most obvious criterion is the

confusion attaching to the use of the very word 'Cellulose.' This is due

to various causes, one of which is the curious specialisation of the

term in Germany as the equivalent of 'wood cellulose.' The restriction

of this general or group term has had an influence even in scientific

circles. Another influence preventing the recognition of the obvious

and, as we think, inevitable basis of classification of the 'celluloses'

is the empiricism of the methods of agricultural chemistry, which as

regards cellulose are so far chiefly concerned with its negative

characteristics and the analytical determination of the indigestible

residue of fodder plants. Physiologists, again, have their own views and

methods in dealing with cellulose, and have hitherto had but little

regard to the work of the chemist in differentiating and classifying the

celluloses on a systematic basis. There are many sides to the subject,

and it is only by a sustained effort towards centralisation that the

general recognition of a systematic basis can be secured.

We may, we hope usefully, direct attention to the conspicuous neglect of

the subject in this country. To the matter of the present volume,

excluding our own investigations, there are but two contributions from

English laboratories. We invite the younger generation of students of

chemistry to measure the probability of finding a working career in

connection with the cellulose industries. They will not find this

invitation in the treatment accorded to the subject in text-books and

lectures. It is probable, indeed, that the impression produced by their

studies is that the industries in coal-tar products largely exceed in

importance those of which the carbohydrates are the basis; whereas the

former are quite insignificant by comparison. A little reflection will

prove that cellulose, starch, and sugar are of vast industrial moment in

the order in which they are mentioned. If it is an open question to

what extent science follows industry, or _vice versa_, it is not open to

doubt that scientific men, and especially chemists, are called in these

days to lead and follow where industrial evolution is most active. There

is ample evidence of activity and great expansion in the cellulose

industries, especially in those which involve the chemistry of the raw

material; and the present volume should serve to show that there is

rapid advance in the science of the subject. Hence our appeal to the

workers not to neglect those opportunities which belong to the days of

small beginnings.

We have especially to acknowledge the services of Mr. J. F. BRIGGS in

investigations which are recorded on pp. 34-40 and pp. 125-133 of the

text.

CONTENTS

THE MATTER OF THIS VOLUME MAY BE DIVIDED INTO THE FOLLOWING SECTIONS

PAGE

INTRODUCTION--DEALING WITH THE SUBJECT IN GENERAL OUTLINE 1

SECTION

I. GENERAL CHEMISTRY OF THE TYPICAL COTTON CELLULOSE 13

II. SYNTHETICAL DERIVATIVES--SULPHOCARBONATES AND ESTERS 27

III. DECOMPOSITIONS OF CELLULOSE SUCH AS THROW LIGHT

ON THE PROBLEM OF ITS CONSTITUTION 67

IV. CELLULOSE GROUP, INCLUDING HEMICELLULOSES AND

TISSUE CONSTITUENTS OF FUNGI 97

V. FURFUROIDS, i.e. PENTOSANES AND FURFURAL-YIELDING

CONSTITUENTS GENERALLY 114

VI. THE LIGNOCELLULOSES 125

VII. PECTIC GROUP 152

VIII. INDUSTRIAL AND TECHNICAL. GENERAL REVIEW 155

INDEX OF AUTHORS 177

INDEX OF SUBJECTS 178

CELLULOSE

INTRODUCTION

In the period 1895-1900, which has elapsed since the original

publication of our work on 'Cellulose,' there have appeared a large

number of publications dealing with special points in the chemistry of

cellulose. So large has been the contribution of matter that it has been

considered opportune to pass it under review; and the present volume,

taking the form of a supplement to the original work, is designed to

incorporate this new matter and bring the subject as a whole to the

level to which it is thereby to be raised. Some of our critics in

reviewing the original work have pronounced it 'inchoate.' For this

there are some explanations inherent in the matter itself. It must be

remembered that every special province of the science has its systematic

beginning, and in that stage of evolution makes a temporary 'law unto

itself.' In the absence of a dominating theory or generalisation which,

when adopted, gives it an organic connection with the general advance of

the science, there is no other course than to classify the

subject-matter. Thus 'the carbohydrates' may be said to have been in the

inchoate condition, qualified by a certain classification, prior to the

pioneering investigations of Fischer. In attacking the already

accumulated and so far classified material from the point of view of a

dominating theory, he found not only that the material fell into

systematic order and grew rapidly under the stimulus of fruitful

investigation, but in turn contributed to the firmer establishment of

the theoretical views to which the subject owed its systematic new

birth. On the other hand, every chemist knows that it is only the

simpler of the carbohydrates which are so individualised as to be

connoted by a particular formula in the stereoisomeric system. Leaving

the monoses, there is even a doubt as to the constitution of cane sugar;

and the elements of uncertainty thicken as we approach the question of

the chemical structure of starch. This unique product of plant life has

a literature of its own, and how little of this is fully known to what

we may term the 'average chemist' is seen by the methods he will employ

for its quantitative estimation. In one particular review of our work

where we are taken to task for producing 'an aggravating book, inchoate

in the highest degree ... disfigured by an obscurity of diction which

must materially diminish its usefulness' ['Nature,' 1897, p. 241], the

author, who is a well-known and competent critic, makes use of the short

expression in regard to the more complex carbohydrates, 'Above cane

sugar, higher in the series, all is chaos,' and in reference to starch,

'the subject is still enshrouded in mystery.' This 'material' complexity

is at its maximum with the most complex members of the series, which are

the celluloses, and we think accounts in part for the impatience of our

critic. 'Obscurity of diction' is a personal quantity, and we must leave

that criticism to the fates. We find also that many workers whose

publications we notice in this present volume quite ignore the _plan_ of

the work, though they make use of its matter. We think it necessary to

restate this plan, which, we are satisfied, is systematic, and, in fact,

inevitable. Cellulose is in the first instance a _structure_, and the

anatomical relationships supply a certain basis of classification. Next,

it is known to us and is defined by the negative characteristics of

resistance to hydrolytic actions and oxidations. These are dealt with in

the order of their intensity. Next we have the more positive definition

by ultimate products of hydrolysis, so far as they are known, which

discloses more particularly the presence of a greater or less proportion

of furfural-yielding groups. Putting all these together as criteria of

function and composition we find they supply common or general dividing

lines, within which groups of these products are contained. The

classification is natural, and in that sense inevitable; and it not only

groups the physiological and chemical facts, but the industrial also. We

do not propose to argue the question whether the latter adds any cogency

to a scientific scheme. We are satisfied that it does, and we do not

find any necessity to exclude a particular set of phenomena from

consideration, because they involve 'commercial' factors. We have dealt

with this classification in the original work (p. 78), and we discuss

its essential basis in the present volume (p. 28) in connection with the

definition of a 'normal' cellulose. But the 'normal' cellulose is not

the only cellulose, any more than a primary alcohol or an aliphatic

alcohol are the only alcohols. This point is confused or ignored in

several of the recent contributions of investigators. It will suffice to

cite one of these in illustration. On p. 16 we give an account of an

investigation of the several methods of estimating cellulose, which is

full of valuable and interesting matter. The purpose of the author's

elaborate comparative study is to decide which has the strongest claims

to be regarded as the 'standard' method. They appear to have a

preference for the method of Lange--viz. that of heating at high

temperatures (180 deg.) with alkaline hydrates, but the investigation shows

that (as we had definitely stated in our original work, p. 214) this is

subject to large and variable errors. The adverse judgment of the

authors, we may point out, is entirely determined on the question of

aggregate weight or yield, and without reference to the ultimate

composition or constitution of the final product. None of the available

criteria are applied to the product to determine whether it is a

cellulose (anhydride) or a hydrate or a hydrolysed product. After these

alkali-fusion processes the method of chlorination is experimentally

reviewed and dismissed for the reason that the product retains

furfural-yielding groups, which is, from our point of view, a particular

recommendation, i.e. is evidence of the selective action of the chlorine

and subsequent hydrolysis upon the lignone group. As a matter of fact it

is the only method yet available for isolating the cellulose from a

lignocellulose by a treatment which is quantitatively to be accounted

for in every detail of the reactions. It does not yield a 'normal'

cellulose, and this is the expression which, in our opinion, the authors

should have used. It should have been pointed out, moreover, that, as

the cellulose is separated from actual condensed combination with the

lignone groups, it may be expected to be obtained in a hydrated form,

and also not as a homogeneous substance like the normal cotton

cellulose. The product is a cellulose of the second group of the

classification. Another point in this investigation which we must

criticise is the ultimate selection of the Schulze method of prolonged

maceration with nitric acid and a chlorate, followed by suitable

hydrolysis of the non-cellulose derivatives to soluble products. Apart

from its exceptional inconvenience, rendering it quite impracticable in

laboratories which are concerned with the valuation of cellulosic raw

materials for industrial purposes, the attack of the reagent is complex

and ill-defined. This criticism we would make general by pointing out

that such processes quite ignore the specific characteristics of the

non-cellulose components of the compound celluloses. The second division

of the plan of our work was to define these constituents by bringing

together all that had been established concerning them. These groups are

widely divergent in chemical character, as are the compound celluloses

in function in the plant. Consequently there is for each a special

method of attack, and it is a reversion to pure empiricism to expect any

one treatment to act equally on the pectocelluloses, lignocelluloses,

and cutocelluloses. Processes of isolating cellulose are really more

strictly defined as methods of selective and regulated attack of the

groups with which they occur, combined or mixed. A chemist familiar with

such types as rhea or ramie (pectocellulose), jute (lignocellulose), and

raffia (cutocellulose) knows exactly the specific treatment to apply to

each for isolating the cellulose, and must view with some surprise the

appearance at this date of such 'universal prescriptions' as the process

in question.

The third division of our plan of arrangement comprised the synthetical

derivatives of the celluloses, the sulphocarbonates first, as peculiarly

characteristic, and then the esters, chiefly the acetates, benzoates,

and nitrates. To these, investigators appear to have devoted but little

attention, and the contribution of new matter in the present volume is

mainly the result of our own researches. It will appear from this work

that an exhaustive study of the cellulose esters promises to assist very

definitely in the study of constitutional problems.

This brings us to the fourth and, to the theoretical chemist, the most

important aspect of the subject, the problem of the actual molecular

structure of the celluloses and compound celluloses. It is herein we are

of opinion that the subject makes a 'law unto itself.' If the

constitution of starch is shrouded in mystery and can only be vaguely

expressed by generalising a complex mass of statistics of its successive

hydrolyses, we can only still more vaguely guess at the distance which

separates us from a mental picture of the cellulose unit. We endeavour

to show by our later investigations that this problem merges into that

of the actual structure of cellulose in the mass. It is definitely

ascertained that a change in the molecule, or reacting unit, of a

cellulose, proportionately affects the structural properties of the

derived compounds, both sulphocarbonates and esters. This is at least an

indication that the properties of the visible aggregates are directly

related to the actual configuration of the chemical units. But it

appears that we are barred from the present discussion of such a problem

in absence of any theory of the solid state generally, but more

particularly of those forms of matter which are grouped together as

'colloids.'

Cellulose is distinguished by its inherent constructive functions, and

these functions take effect in the plastic or colloidal condition of the

substance. These properties are equally conspicuous in the synthetical

derivatives of the compound. Without reference, therefore, to further

speculations, and not deterred by any apparent hopelessness of solving

so large a problem, it is clear that we have to exhaust this field by

exact measurements of all the constants which can be reduced to

numerical expression. It is most likely that the issue may conflict with

some of our current views of the molecular state which are largely drawn

from a study of the relatively dissociated forms of matter. But such

conflicts are only those of enlargement, and we anticipate that all

chemists look for an enlargement of the molecular horizon precisely in

those regions where the forces of cell-life manifest themselves.

The _cellulose group_ has been further differentiated by later

investigations. The fibrous celluloses of which the typical members

receive important industrial applications, graduate by insensible stages

into the hemicelluloses which may be regarded as a well-established

sub-group. In considering their morphological and functional

relationships it is evident that the graduation accords with their

structure and the less permanent functions which they fulfil. They are

aggregates of monoses of the various types, chiefly mannose, galactose,

dextrose, &c., so far as they have been investigated.

Closely connected with this group are the constituents of the tissues of

fungi. The recent researches of Winterstein and Gilson, which are noted

in this present volume, have established definitely that they contain a

nitrogenous group in intimate combination with a carbohydrate complex.

This group is closely related to chitin, yielding glucosamin and acetic

acid as products of ultimate hydrolysis. Special interest attaches to

these residues, as they are in a sense intermediate products between the

great groups of the carbohydrates and proteids (E. Fischer, Ber. 19,

1920), and their further investigation by physiological methods may be

expected to disclose a genetic connection.

The _lignocelluloses_ have been further investigated. Certain new types

have been added, notably a soluble or 'pectic' form isolated from the

juice of the white currant (p. 152), and the pith-like wood of the

AEschynomene (p. 135).

Further researches on the typical fibrous lignocellulose have given us a

basis for correcting some of the conclusions recorded in our original

work, and a study of the esters has thrown some light on the

constitution of the complex (p. 130).

Of importance also is the identification of the hydroxyfurfurals as

constituents of the lignocelluloses generally, and the proof that the

characteristic colour-reactions with phenols (phloroglucinol) may be

ascribed to the presence of these compounds (p. 116).

The _pectocelluloses_ have not been the subject of systematic chemical

investigation, but the researches of Gilson ('La Cristallisation de la

Cellulose et la Composition Chimique de la Membrane Cellulaire

Vegetale,' 'La Revue,' 'La Cellule,' i. ix.) are an important

contribution to the natural history of cellulose, especially in relation

to the 'pectic' constituents of the parenchymatous celluloses.

Indirectly also the researches of Tollens on the 'pectins' have

contributed to the subject in correcting some of the views which have

had a text-book currency for a long period. These are dealt with on p.

151. The results establish that the pectins are rather the soluble

hydrated form of cellulosic aggregates in which acid groups may be

represented; but such groups are not to be regarded as essentially

characteristic of this class of compounds.

~Furfural-yielding Substances~ (Furfuroids).--This group of plant products

has been, by later investigations, more definitely and exclusively

connected with the celluloses--i.e. with the more permanent of plant

tissues. From the characteristic property of yielding furfural, which

they have in common with the pentoses, they have been assumed to be the

anhydrides of these C_{5} sugars or pentosanes; but the direct evidence

for this assumption has been shown to be wanting. In regard to their

origin the indirect evidences which have accumulated all point to their

formation in the plant from hexoses. Of special interest, in its

bearings on this point, is the direct transformation of levulose into

furfural derivatives, which takes place under the action of condensing

agents. The most characteristic is that produced by the action of

anhydrous hydrobromic acid in presence of ether [Fenton], yielding a

brommethyl furfural

C_{6}H_{12}O_{6} - 4H_{2}O + HBr = C_{5}H_{3}.O_{2}.CH_{2}Br

with a Br atom in the methyl group. These researches of Fenton's appear

to us to have the most obvious and direct bearings upon the genetic

relationships of the plant furfuroids and not only _per se_. To give

them their full significance we must recall the later researches of

Brown and Morris, which establish that cane sugar is a primary or direct

product of assimilation, and that starch, which had been assumed to be a

species of universal _matiere premiere_, is probably rather a general

reserve for the elaborating work of the plant. If now the aldose groups

tend to pass over into the starch form, representing a temporary

overflow product of the assimilating energy, it would appear that the

ketose or levulose groups are preferentially used up in the elaboration

of the permanent tissue. We must also take into consideration the

researches of Lobry de Bruyn showing the labile functions of the typical

CO group in both aldoses and hexoses, whence we may conclude that in the

plant-cell the transition from dextrose to levulose is a very simple and

often occurring process.

We ourselves have contributed a link in this chain of evidence

connecting the furfuroids of the plant with levulose or other

keto-hexose. We have shown that the hydroxyfurfurals are constituents of

the lignocelluloses. The proportion present in the free state is small,

and it is not difficult to show that they are products of breakdown of

the lignone groups. If we assume that such groups are derived ultimately

from levulose, we have to account for the detachment of the methyl

group. This, however, is not difficult, and we need only call to mind

that the lignocelluloses are characterised by the presence of methoxy

groups and a residue which is directly and easily hydrolysed to acetic

acid. Moreover, the condensation need not be assumed to be a simple

dehydration with attendant rearrangement; it may very well be

accompanied or preceded by fixation of oxygen. Leaving out the

hypothetical discussion of minor variations, there is a marked

convergence of the evidence as to the main facts which establish the

general relationships of the furfuroid group. This group includes both

saturated and unsaturated or condensed compounds. The former are

constituents of celluloses, the latter of the lignone complex of the

lignocelluloses.

The actual production of furfural by boiling with condensing acids is a

quantitative measure of only a portion, i.e. certain members of the

group. The hydroxyfurfurals, not being volatile, are not measured in

this way. By secondary reactions they may yield some furfural, but as

they are highly reactive compounds, and most readily condensed, they are

for the most part converted into complex 'tarry' products. Hence we have

no means, as yet, of estimating those tissue constituents which yield

hydroxyfurfurals; also we have no measure of the furfurane-rings

existing performed in such a condensed complex as lignone. But, chemists

having added in the last few years a large number of facts and

well-defined probabilities, it is clear that the further investigation

of the furfuroid group will take its stand upon a much more adequate

basis than heretofore. On the view of 'furfural-yielding' being

co-extensive with 'pentose or pentosane,' not only were a number of

important facts obscured or misinterpreted, but there was a barrenness

of suggestion of genetic relationships. As the group has been widened

very much beyond these limits, it is clear that if any group term or

designation is to be retained that of 'furfuroid' is 'neutral' in

character, and equally applicable to saturated substances of such widely

divergent chemical character as pentoses, hexosones, glycuronic acid,

and perhaps, most important of all, levulose itself, all of which are

susceptible of condensation to furfural or furfurane derivatives, as

well as to those unsaturated compounds, constituents of plant tissues

which are already furfurane derivatives.

From the chemical point of view such terms are perhaps superfluous. But

physiological relationships have a significance of their own; and there

is a physiological or functional cohesion marking this group which

calls for recognition, at least for the time, and we therefore propose

to retain the term furfuroid.[1]

~General Experimental Methods.~--In the investigation of the cellulose

group it is clear that methods of ultimate hydrolysis are of first

importance. None are so convenient as those which are based on the

action of sulphuric acid, more or less concentrated (H_{2}SO_{4}.3H_{2}O

- H_{2}SO_{4}H_{2}O). Such methods have been frequently employed in the

investigations noted in this volume. We notice a common deficiency in

the interpretation of the results. It appears to be sufficient to

isolate and identify a crystalline monose, without reference to the

yield or proportion to the parent substance, to establish some main

point in connection with its constitution. On the other hand, it is

clear that in hydrolysing a given cellulose-complex we ought to aim at

complete, i.e. _quantitative, statistics_. The hydrolytic transformation

of starch to dextrins and maltose has been followed in this way, and the

methods may serve as a model to which cellulose transformations should

be approximated. In fact, what is very much wanted is a systematic

re-examination of the typical celluloses in which all the constants of

the terms between the original and the ultimate monose groups shall be

determined. Such constants are similar to those for the starch-dextrose

series, viz. opticity and cupric reduction. Various methods of

fractionation are similarly available, chiefly the precipitation of the

intermediate 'dextrins' by alcohol.

Where the original celluloses are homogeneous we should thus obtain

transformation series, similarly expressed to those of starch. In the

case of the celluloses which are mixtures, or of complex constitution,

there are various methods of either fractionating the original, or of

selectively attacking particular monoses resulting from the

transformation. By methods which are approximately quantitative a

mixture of groups, such as we have, for instance, in jute cellulose,

could be followed through the several stages of their resolution into

monoses. To put the matter generally, in these colloidal and complex

carbohydrates the ordinary physical criteria of molecular weight are

wanting. Therefore, we cannot determine the relationship of a given

product of decomposition to the parent molecule save by means of a

quantitative mass-proportion. Physical criteria are only of determining

value when associated with such constants as cupric reduction, and

these, again, must be referred to some arbitrary initial weight, such

as, for convenience, 100 parts of the original.

Instead of adopting these methods, without which, as a typical case, the

mechanism of starch conversions could not have been followed, we have

been content with a purely qualitative study of the analogous series

obtainable from the celluloses under the action of sulphuric acid. A

very important field of investigation lies open, especially to those who

are generally familiar with the methods of studying starch conversions;

and we may hope in this direction for a series of valuable contributions

to the problem of the actual constitution of the celluloses.

FOOTNOTES:

[1] In this we are confirmed by other writers. See Tollens, _J. fuer

Landw._ 1901, p. 27.

SECTION I. GENERAL CHEMISTRY OF THE TYPICAL COTTON CELLULOSE

(p. 3)[2] ~Ash Constituents.~--It is frequently asserted that silica has a

structural function _sui generis_ in the plant skeleton, having a

relationship to the cellulosic constituents of the plant, distinct from

that of the inorganic ash components with which it is associated. It

should be noted that the matter has been specifically investigated in

two directions. In Berl. Ber. 5, 568 (A. Ladenburg), and again in 11,

822 (W. Lange), appear two papers 'On the Nature of Plant Constituents

containing Silicon,' which contain the results of experimental

investigations of equisetum species--distinguished for their

exceptionally high 'ash' with large proportion of silica--to determine

whether there are any grounds for assuming the existence of

silicon-organic compounds in the plant, the analogues of carbon

compounds. The conclusions arrived at are entirely negative. In

reference to the second assumption that the cuticular tissues of cereal

straws, of esparto, of the bamboo, owe their special properties to

siliceous components, it has been shown by direct experiment upon the

former that their rigidity and resistance to water are in no way

affected by cultivation in a silica-free medium. In other words, the

structural peculiarities of the gramineae in these respects are due to

the physical characteristics chiefly of the (lignified) cells of the

hypodermal tissue, and to the composition and arrangement of the cells

of the cuticle.

_'Swedish' filter papers_ of modern make are so far freed from inorganic

constituents that the weight of the ash may be neglected in nearly all

quantitative experiments [Fresenius, Ztschr. Anal Chem. 1883, 241]. It

represents usually about 1/1000 mgr. per 1 sq. cm. of area of the paper.

_The form of an 'ash'_ derived from a fibrous structure, is that of the

'organic' original, more or less, according to its proportion and

composition. The proportion of 'natural ash' is seldom large enough, nor

are the components of such character as to give a coherent ash, but if

in the case of a fibrous structure it is combined or intimately mixed

with inorganic compounds deposited within the fibres from solution, the

latter may be made to yield a perfect skeleton of the fibre after

burning off the organic matter. It is by such means that the mantles

used in the Welsbach system of incandescent lighting are prepared. A

purified cotton fabric--or yarn--is treated with a concentrated solution

of the mixed nitrates of thorium and cerium, and, after drying, the

cellulose is burned away. A perfect and coherent skeleton of the fabric

is obtained, composed of the mixed oxides. Such mantles have fulfilled

the requirements of the industry up to the present time, but later

experiments forecast a notable improvement. It has been found that

artificial cellulose fibres can be spun with solutions containing

considerable proportions of soluble compounds of these oxides. Such

fibres, when knitted into mantles and ignited, yield an inorganic

skeleton of the oxides of homogeneous structure and smooth contour. De

Mare in 1894, and Knofler in 1895, patented methods of preparing such

cellulose threads containing the salts of thorium and cerium, by

spinning a collodion containing the latter in solution. When finally

ignited, after being brought into the suitable mantle form, there

results a structure which proves vastly more durable than the original

Welsbach mantle. The cause of the superiority is thus set forth by V.

H. Lewes in a recent publication (J. Soc. of Arts, 1900, p. 858): 'The

alteration in physical structure has a most extraordinary effect upon

the light-giving life of the mantle, and also on its strength, as after

burning for a few hundred hours the constant bombardment of the mantle

by dust particles drawn up by the rush of air in the chimney causes the

formation of silicates on the surface of the mantle owing to silica

being present in the air, and this seems to affect the Welsbach

structure far more than it does the "Clamond" type, with the result that

when burned continuously the Welsbach mantle falls to so low a pitch of

light emissivity after 500 to 600 hours, as to be a mere shadow of its

former self, giving not more than one-third of its original light,

whilst the Knofler mantle keeps up its light-emitting power to a much

greater extent, and the Lehner fabric is the most remarkable of all. Two

Lehner mantles which have now been burning continuously in my laboratory

for over 3,000 hours give at this moment a brighter light emissivity

than most of the Welsbachs do in their prime.' ...'The new developments

of the Clamond process form as important a step in the history of

incandescent gas lighting as the discoveries which gave rise to the

original mantles.'

It has further been found that the oxides themselves can be dissolved in

the cellulose alkaline sulphocarbonate (viscose) solution, and

artificial threads have been spun containing from 25 to 30 p.ct. of the

oxides in homogeneous admixture with the cellulose. This method has

obvious advantages over the collodion method both in regard to the

molecular relationship of the oxides to the cellulose and to cheapness

of production.

UNTERSUCHUNGEN UeBER VERSCHIEDENE BESTIMMUNGSMETHODEN DER CELLULOSE.

H. SURINGAR AND B. TOLLENS (Ztschr. angew. Chem. 1896, No. 23).

~INVESTIGATION OF METHODS OF DETERMINING CELLULOSE.~

_Introduction._--This is an exhaustive bibliography of the subject,

describing also the various methods of cellulose estimation, noted in

historical sequence. First, the Weende 'crude fibre' method (Henneberg)

with modifications of Wattenberg, Holdefleiss, and others is dealt with.

The product of this treatment, viz. 'crude fibre' is a mixture,

containing furfuroids and lignone compounds. Next follows a group of

processes which aim at producing a 'pure cellulose' by eliminating

lignone constituents, for which the merely hydrolytic treatments of the

Weende method are ineffectual. The method of F. Schulze--prolonged

digestion with dilute nitric acid, with addition of chlorate--has been

largely employed, though the composition of the product is more or less

divergent from a 'pure cellulose.'

Dilute nitric acid at 60-80 deg. (Cross and Bevan) and a dilute mixture of

nitric and sulphuric acids (Lifschutz) have been employed for isolating

cellulose from the lignocelluloses. Hoffmeister modifies the method of

Schulze by substituting hydrochloric acid for the nitric acid. Treatment

with the halogens associated with alkaline processes of hydrolysis is

the basis of the methods of Hugo Muller (bromine water) and Cross and

Bevan (chlorine gas). Lastly, the authors notice the methods based upon

the action of the alkaline hydrates at high temperatures (180 deg.) in

presence of water (Lange), or of glycerin (Gabriel). The process of

heating to 210 deg. with glycerin only (Hoenig) yields a very impure and

ill-defined product.

For comparative investigation of these processes certain celluloses and

cellulosic materials were prepared as follows:

(a) _'Rag' cellulose._--A chemical filter paper, containing only

cotton and linen celluloses, was further purified by boiling with dilute

acid and dilute alkali. After thorough washing it was air-dried.

(b) _Wood cellulose._--Pine wood sawdust was treated by digestion for

fourteen days with dilute nitric acid with addition of chlorate

(Schulze). The mass was washed and digested with alkaline lye (1.25

p.ct. KOH), and exhaustively washed, treated with dilute acetic acid;

again washed, and finally air-dried.

This product was found to yield 2.3 p.ct. furfural on distillation with

HCl (1.06 sp.gr.).

dilute alkalis and acids, in the cold, and with alcohol and ether until

exhausted of products soluble in these liquids and reagents.

In addition to the above the authors have also employed jute fibre and

raw cotton wool in their investigations.

They note that the yield of cellulose is in many cases sensibly lowered

by treating the material after drying at the temperature of 100 deg.. The

material for treatment is therefore weighed in the air-dry condition,

and a similar sample weighed off for drying at 100 deg. for determination of

moisture.

The main results of the experimental investigation are as follows:--

_Weende process_ further attacks the purified celluloses as follows:

Wood cellulose losing in weight 8-9 p.ct.; filter paper, 6-7.5 p.ct.,

and the latter treated a second time loses a further 4-5 p.ct. It is

clear, therefore, that the process is of purely empirical value.

_Schulze._--This process gave a yield of 47.6 p.ct. cellulose from pine

wood. The celluloses themselves, treated by the process, showed losses

of 1-3 p.ct. in weight, much less therefore than in the preceding case.

_Hoenig's_ method of heating with glycerin to 210 deg. was found to yield

products very far removed from 'cellulose.' The process may have a

certain value in estimations of 'crude fibre,' but is dismissed from

further consideration in relation to cellulose.

_Lange._--The purpose of the investigation was to test the validity of

the statement that the celluloses are not attacked by alkaline hydrates

at 180 deg.. Experiments with pine wood yielded a series of percentages for

cellulose varying from 36 to 41; the 'purified wood' gave also variable

numbers, 44 to 49 per cent. It was found possible to limit these

variations by altering the conditions in the later stages of isolating

the product; but further experiments on the celluloses themselves

previously isolated by other processes showed that they were profoundly

and variably attacked by the 'Lange' treatment, wood cellulose losing 50

per cent. of its weight, and filter paper (cellulose) losing 15 per

cent. Further, a specimen of jute yielded 58 per cent. of cellulose by

this method instead of the normal 78 per cent. It was also found that

the celluloses isolated by the process, when subjected to a second

treatment, underwent a further large conversion into soluble

derivatives, and in a third treatment further losses of 5-10 per cent

were obtained. The authors attach value, notwithstanding, to the process

which they state to yield an 'approximately pure cellulose,' and they

describe a modified method embodying the improvements in detail

resulting from their investigation.

_Gabriel's_ method of heating with a glycerin solution of alkaline

hydrate is a combination of 'Hoenig' and 'Lange.' An extended

investigation showed as in the case of the latter that the

celluloses themselves are more or less profoundly attacked by the

treatment--further that the celluloses isolated from lignocelluloses and

other complex raw materials are much 'less pure' than those obtained by

the Lange process. Thus, notably in regard to furfural yielding

constituents, the latter yield 1-2 p.ct. furfural, whereas _specimens of

'jute cellulose'_ obtained by the Gabriel process were found to yield _9

to 13 p.ct. furfural_.

_Cross and Bevan._--Chlorination process yielded in the hands of the

authors results confirming the figures given in 'Cellulose' for yield of

cellulose. Investigation of the products for yield of furfural, gave 9

p.ct. of this aldehyde showing the presence of celluloses, other than

the normal type.

_Conclusions._--The subjoined table gives the mean numerical results for

yield of end-product or 'cellulose' by the various methods. In the case

of the 'celluloses' the results are those of the further action of the

several processes on the end-product of a previous process.

| Methods

--------------------------------------------------------------------------

Wood cellulose | 98.51 | 91.52 | 48.22 | 55.93 | --

Filter paper cellulose | 99.62 | 95.63 | 78.17 | 79.77 | --

Swedish filter paper | 96.58 | -- | 84.76 | -- | --

Ordinary filter paper | 98.17 | 93.39 | 86.58 | -- | --

Cotton ('wool') | 98.38 | 89.98 | 63.96 | 67.88 | --

Jute | -- | -- | 57.93 | 71.64 | 75.27

Purified wood | -- | -- |{49.27 | -- | --

| | |{46.56 | |

Raw wood | 47.60 | -- |{40.82 | -- | --

| | |{38.87 | |

--------------------------------------------------------------------------

The final conclusion drawn from the results is that none of the

processes fulfil the requirements of an ideal method. Those which may

be carried out in a reasonably short time are deficient in two

directions: (1) they yield a 'cellulose' containing more or less

oxycellulose; (2) the celluloses themselves are attacked under the

conditions of treatment, and the end product or cellulose merely

represents a particular and at the same time variable equilibrium, as

between the resistance of the cellulose and the attack of the reagents

employed; this attack being by no means confined to the non-cellulose

constituents. Schulze's method appears to give the nearest approximation

to the 'actual cellulose' of the raw material.

* * * * *

(p. 8) ~SOLUTIONS OF CELLULOSE~--(1) ~ZINC CHLORIDE.~--To prepare a

homogeneous solution of cellulose by means of the neutral chloride, a

prolonged digestion at or about 100 deg. with the concentrated reagent is

required. The dissolution of the cellulose is not a simple phenomenon,

but is attended with hydrolysis and a certain degree of condensation.

The latter result is evidenced by the formation of furfural, the former

by the presence of soluble carbohydrates in the solution obtained by

diluting the original solution and filtering from the reprecipitated

cellulose. The authors have observed that in carefully conducted

experiments cotton cellulose may be dissolved in the reagent, and

reprecipitated with a loss of only 1 p.ct. in weight. This, however, is

a 'net' result, and leaves undetermined the degree of hydration of the

recovered cellulose as of hydrolysis of the original to groups of lower

molecular weights. Bronnert finds that a previous hydration of the

cellulose--e.g. by the process of alkaline mercerisation and removal of

the alkali by washing--enables the zinc chloride to effect its

dissolution by digestion in the cold. (U.S. patent, 646,799/1900. See

also p. 59.)

_Industrial applications._--(a) _Vulcanised fibre_ is prepared by

treating paper with four times its weight of the concentrated aqueous

solution (65-75 deg. B.), and in the resulting gelatinised condition is

worked up into masses, blocks, sheets, &c., of any required thickness.

The washing of these masses to remove the zinc salt is a very lengthy

operation.

To render the product waterproof the process of nitration is sometimes

superadded [D.R.P. 3181/1878]. Further details of manufacture are given

in Prakt. Handbuch d. Papierfabrikation, p. 1703 [C. Hofmann].

(b) _Calico-printing._--The use of the solution as a thickener or

colour vehicle, more especially as a substitute for albumen in pigment

styles, was patented by E. B. Manby, but the process has not been

industrially developed [E.P. 10,466/1894].

applications of the solution in spinning cellulose threads for

conversion into carbon filaments for electrical glow-lamps. This section

will be found dealt with on p. 59.

(p. 13) (2) ~Cuprammonium solution.~--The application of the solution of

cellulose in cuprammonium to the production of a fine filament in

continuous length, 'artificial silk,' has been very considerably studied

and developed in the period 1897-1900, as evidenced by the series of

patents of Fremery and Urban, Pauly, Bronnert, and others. The subject

will also be found dealt with on p. 58.

* * * * *

(p. 15) ~Reactions of cellulose with iodine.~--In a recent paper, F.

Mylius deals with the reaction of starch and cellulose with iodine,

pointing out that the blue colouration depends upon the presence of

water and iodides. In absence of the latter, and therefore in presence

of compounds which destroy or absorb hydriodic acid--e.g. iodic

acid--there results a _brown_ addition product. The products in question

have the characteristics of _solid solutions_ of the halogen. (Berl.

Ber. 1895, 390.)

(24) ~Mercerisation~--Notwithstanding the enormous recent developments in

the industrial application of the mercerising reaction, there have been

no noteworthy contributions to the theoretical aspects of the subject.

The following abstract gives an outline of the scope of an important

technical work on the subject.

DIE MERCERISATION DER BAUMWOLLE.

PAUL GARDNER (Berlin: 1898. J. Springer).

~THE MERCERISATION OF COTTON.~

This monograph of some 150 pages is chiefly devoted to the patent

literature of the subject. The chemical and physical modifications of

the cotton substance under the action of strong alkaline lye, were set

forth by Mercer in 1844-5, and there has resulted from subsequent

investigations but little increase in our knowledge of the fundamental

facts. The treatment was industrially developed by Mercer in certain

directions, chiefly (1) for preparing webs of cloth required to stand

considerable strain, and (2) for producing crepon effects by local or

topical action of the alkali. But the results achieved awakened but a

transitory interest, and the matter passed into oblivion; so much so,

indeed, that a German patent [No. 30,966] was granted in 1884 to the

Messrs. Depouilly for crepon effects due to the differential shrinkage

of fabrics under mercerisation, by processes and treatments long

previously described by Mercer. Such effects have had a considerable

vogue in recent years, but it was not until the discovery of the

lustreing effect resulting from the association of the mercerising

actions with the condition of strain or tension of the yarn or fabric

that the industry in 'mercerised' goods was started on the lines which

have led to the present colossal development. The merit of this

discovery is now generally recognised as belonging to Thomas and Prevost

of Crefeld, notwithstanding that priority of patent right belongs to the

English technologist, H. A. Lowe.

The author critically discusses the grounds of the now celebrated patent

controversy, arising out of the conflict of the claims of German patent

85,564/1895 of the former, and English patent 4452/1890 of the latter.

The author concludes that Lowe's specification undoubtedly describes the

lustreing effect of mercerising in much more definite terms than that of

Thomas and Prevost. These inventors, on the other hand, realised the

effect industrially, which Lowe certainly failed to do, as evidenced by

his allowing the patent to lapse. As an explanation of his failure, the

author suggests that Lowe did not sufficiently extend his observations

to goods made from Egyptian and other long-stapled cottons, in which

class only are the full effects of the added lustre obtained.

Following these original patents are the specifications of a number of

inventions which, however, are of insignificant moment so far as

introducing any essential variation of the mercerising treatment.

The third section of the work describes in detail the various mechanical

devices which have been patented for carrying out the treatment on yarn

and cloth.

The fourth section deals with the fundamental facts underlying the

process and effects summed up in the term 'mercerisation.' These are as

follows:--

(a) Although all forms of fibrous celluloses are similarly affected by

strong alkaline solutions, it is only the Egyptian and other

long-stapled cottons--i.e. the goods made from them--which under the

treatment acquire the special high lustre which ranks as 'silky.' Goods

made from American cottons acquire a certain 'finish' and lustre, but

the effects are not such as to have an industrial value--i.e. a value

proportional to the cost of treatment.

(b) The lustre is determined by exposing the goods to strong tension,

either when under the action of the alkali, or subsequently, but only

when the cellulose is in the special condition of hydration which is the

main chemical effect of the mercerising treatment.

the shrinkage in dimensions, otherwise determined by the action of the

alkali. The following table exhibits the variations of shrinkage of

Egyptian when mercerised without tension, under varying conditions as

regards the essential factors of the treatment--viz. (1) concentration

of the alkaline lye, (2) temperature, and (3) duration of action (the

latter being of subordinate moment):--

_______________________________________________________________________

| | | | | |

| | | | | | | | | | | |

| action in | 1 | 10 | 30 | 1 | 10 | 30 | 1 | 10 | 30 | |

| | | | | | | | | | | |

| Temperatures | Percentage shrinkages (Egyptian yarns) as under:-- |

| 2 deg. | 0 | 0 | 0 | 1 | 1 | 1 | 12.2 | 15.2 | 15.8 | 19.2 |

| 18 deg. | 0 | 0 | 0 | 0 | 0 | 0 | 8.0 | 8.8 | 11.8 | 19.8 |

| 30 deg. | 0 | 0 | 0 | 0 | 0 | 0 | 4.6 | 4.6 | 6.0 | 19.0 |

| 80 deg. | 0 | 0 | 0 | 0 | 0 | 0 | 3.5 | 3.5 | 9.8 | 13.4 |

|_______________|___|____|____|___|____|____|______|______|______|______|

_______________________________________________________________________

| | | | |

| | | | | | | | | |

| action in | 10 | 30 | 1 | 10 | 30 | 1 | 10 | 30 |

| | | | | | | | | |

| Temperatures | Percentage shrinkages (Egyptian yarns) as under:-- |

| 2 deg. | 19.8 | 21.5 | 22.7 | 22.7 | 22.7 | 24.2 | 24.5 | 24.7 |

| 18 deg. | 20.1 | 21.0 | 21.2 | 22.0 | 22.3 | 23.5 | 23.8 | 24.7 |

| 30 deg. | 19.5 | 19.0 | 18.5 | 19.5 | 19.8 | 20.7 | 21.0 | 21.1 |

| 80 deg. | 13.7 | 14.2 | 15.0 | 15.1 | 15.5 | 15.0 | 15.2 | 15.4 |

|_______________|______|______|______|______|______|______|______|______|

The more important general indications of the above results are--(1) The

mercerisation action commences with a lye of 10 deg.B., and increases with

increased strength of the lye up to a maximum at 35 deg.B. There is,

however, a relatively slight increase of action with the increase of

caustic soda from 30-40 deg.B. (2) For optimum action the temperature should

not exceed 15-20 deg.C. (3) The duration of action is of proportionately

less influence as the concentration of the lye increases. As the maximum

effect is attained the action becomes practically instantaneous, the

only condition affecting it being that of penetration--i.e. actual

contact of cellulose and alkali.

(d) The question as to whether the process of 'mercerisation' involves

chemical as well as physical effects is briefly discussed. The author is

of opinion that, as the degree of lustre obtained varies with the

different varieties of cotton, the differentiation is occasioned by

differences in chemical constitution of these various cottons. The

influence of the chemical factors is also emphasised by the increased

dyeing capacity of the mercerised goods, which effect, moreover, is

independent of those conditions of strain or tension under mercerisation

which determine lustre. It is found in effect that with a varied range

of dye stuffs a given shade is produced with from 10 to 30 p.ct. less

colouring matter than is required for the ordinary, i.e. unmercerised,

goods.

In reference to the constants of strength and elasticity, Buntrock gives

the following results of observations upon a 40^{5} twofold yarn, five

threads of 50 cm. length being taken for each test(Prometheus, 1897, p.

690): (a) the original yarn broke under a load of 1440 grms.; (b)

after mercerisation without tension the load required was 2420 grms.;

therefore, increases the strength of the yarn from 30 to 66 p.ct., the

increase being lessened proportionately to the strain accompanying

mercerisation. _Elasticity_, as measured by the extension under the

breaking load, remains about the same in yarns mercerised under strain,

but when allowed to shrink under mercerisation there is an increase of

30-40 p.ct. over the original.

The _change of form_ sustained by the individual fibres has been studied

by H. Lange [Farberzeitung, 1898, 197-198], whose microphotographs of

the cotton fibres, both in length and cross-section, are reproduced. In

general terms, the change is from the flattened riband of the original

fibre to a cylindrical tube with much diminished and rounded central

canal. The effect of strain under mercerisation is chiefly seen in the

contour of the surface, which is smooth, and the obliteration at

intervals of the canal. Hence the increased transparency and more

complete reflection of the light from the surface, and the consequent

approximation to the optical properties of the silk fibre.

The work concludes with a section devoted to a description of the

various practical systems of mercerisation of yarns in general practice

in Germany, and an account of the methods adopted in dyeing the

mercerised yarns.

RESEARCHES ON MERCERISED COTTON.

A. FRAENKEL and P. FRIEDLAENDER (Mitt. k.-k. Techn. Gew. Mus., Wien,

1898, 326).

The authors, after investigation, are inclined to attribute the lustre

of mercerised cotton to the absence of the cuticle, which is destroyed

and removed in the process, partly by the chemical action of the alkali,

and partly by the stretching at one or other stage of the process. The

authors have investigated the action of alcoholic solutions of soda

also. The lustre effects are not obtained unless the action of water is

associated.

In conclusion, the authors give the following particulars of breaking

strains and elasticity:--

--------------------------------------------------------------------------

Treatment | Experiments | Breaking strain | Elasticity

--------------------------------------------------------------------------

| | | Elongation

| | Grammes | in mm.

| | |

Cotton unmercerised. | 1 | 360 | 20

| 2 | 356 | 20

| 3 | 360 | 22

| | |

Mercerised with | | |

Soda 35 deg.B. | 1 | 530 | 44

| 2 | 570 | 40

| 3 | 559 | 35

| | |

Alcoholic soda 10 p.ct. | 1 | 645 | 24

cold | 2 | 600 | 27

| 3 | 610 | 33

| | |

Alcoholic soda 10 p.ct. | 5 | 740 | 33

hot | 2 | 730 | 38

| 3 | 690 | 30

--------------------------------------------------------------------------

FOOTNOTES:

[2] This and other similar references are to the matter of the original

volume (1895).