Project Gutenberg''''s Researches on Cellulose, by C. F. Cross and E. J. Bevan pptx

This volume, which is intended as asupplement to the work which wepublished in 1895, gives a brief account of researches which have beensubsequently published, as well as ofcertain of ou

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BY

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

SECOND EDITION

LONGMANS, GREEN, AND CO

39 PATERNOSTER ROW, LONDONNEW YORK, BOMBAY, AND

CALCUTTA1907All rights reserved

Transcriber's note: The

sections in the Table ofContents are not used in theactual text They have beenadded for clarity Minor typoshave been corrected andfootnotes moved to the end ofthe sections

PREFACE TO

SECOND EDITION

This edition is a reprint of the first in

response to a continuous demand for thebook The matter, consisting as it doeslargely of records, does not call for anyrevision, and, as a contribution to thedevelopment of theory, any particularinterest which it has is associated with thedate at which it was written

The volume which has since appeared isthe sequel, and aims at an exposition ofthe subject "to date"

This volume, which is intended as asupplement to the work which wepublished in 1895, gives a brief account

of researches which have beensubsequently published, as well as ofcertain of our own investigations, theresults of which are now for the first timerecorded

We have not attempted to give the matter the form of a connected record Thecontributions to the study of 'Cellulose'which are noticed are spread over a largearea, are mostly 'sectional' in their aim,and the only cohesion which we can give

subject-them is that of classifying subject-them according

to the plan of our original work Theirsubject-matter is reproduced in the form

of a précis, as much condensed as

possible; of the more important papers theoriginal title is given In all cases we haveendeavoured to reproduce the Author'smain conclusions, and in most caseswithout comment or criticism

Specialists will note that the basis ofinvestigation is still in a great measureempirical; and of this the most obviouscriterion is the confusion attaching to theuse of the very word 'Cellulose.' This isdue to various causes, one of which is thecurious specialisation of the term inGermany as the equivalent of 'woodcellulose.' The restriction of this general

or group term has had an influence even inscientific circles Another influencepreventing the recognition of the obviousand, as we think, inevitable basis ofclassification of the 'celluloses' is theempiricism of the methods of agriculturalchemistry, which as regards cellulose are

so far chiefly concerned with its negativecharacteristics and the analyticaldetermination of the indigestible residue

of fodder plants Physiologists, again,have their own views and methods indealing with cellulose, and have hithertohad but little regard to the work of thechemist in differentiating and classifyingthe celluloses on a systematic basis Thereare many sides to the subject, and it isonly by a sustained effort towardscentralisation 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 inthis country To the matter of the presentvolume, excluding our own investigations,there are but two contributions fromEnglish laboratories We invite theyounger generation of students ofchemistry to measure the probability offinding a working career in connectionwith the cellulose industries They willnot find this invitation in the treatmentaccorded to the subject in text-books andlectures It is probable, indeed, that theimpression produced by their studies isthat the industries in coal-tar productslargely exceed in importance those ofwhich the carbohydrates are the basis;

whereas the former are quite insignificant

by comparison A little reflection willprove that cellulose, starch, and sugar are

of vast industrial moment in the order inwhich they are mentioned If it is an openquestion to what extent science follows

industry, or vice versa, it is not open to

doubt that scientific men, and especiallychemists, are called in these days to leadand follow where industrial evolution ismost active There is ample evidence ofactivity and great expansion in thecellulose industries, especially in thosewhich involve the chemistry of the rawmaterial; and the present volume shouldserve to show that there is rapid advance

in the science of the subject Hence ourappeal to the workers not to neglect thoseopportunities which belong to the days of

small beginnings.

We have especially to acknowledge theservices of Mr J F Briggs ininvestigations which are recorded on pp.34-40 and pp 125-133 of the text

SECTION

I GENERAL CHEMISTRY OF THETYPICAL COTTON CELLULOSE

II SYNTHETICAL DERIVATIVES—SULPHOCARBONATES AND ESTERS

III DECOMPOSITIONS OFCELLULOSE SUCH AS THROW LIGHT

ON THE PROBLEM OF ITSCONSTITUTION

IV CELLULOSE GROUP, INCLUDINGHEMICELLULOSES AND TISSUECONSTITUENTS OF FUNGI

V FURFUROIDS, i.e PENTOSANES

CONSTITUENTS GENERALLY

VI THE LIGNOCELLULOSES

VII PECTIC GROUP

VIII INDUSTRIAL AND TECHNICAL.GENERAL REVIEW

INDEX OF AUTHORS

INDEX OF SUBJECTS

CELLULOSE

In the period 1895-1900, which haselapsed since the original publication ofour work on 'Cellulose,' there haveappeared a large number of publicationsdealing with special points in thechemistry of cellulose So large has beenthe contribution of matter that it has beenconsidered opportune to pass it underreview; and the present volume, taking theform of a supplement to the original work,

is designed to incorporate this new matterand bring the subject as a whole to thelevel to which it is thereby to be raised.Some of our critics in reviewing theoriginal work have pronounced it

'inchoate.' For this there are someexplanations inherent in the matter itself Itmust be remembered that every specialprovince of the science has its systematicbeginning, and in that stage of evolutionmakes a temporary 'law unto itself.' In theabsence of a dominating theory orgeneralisation which, when adopted, gives

it an organic connection with the generaladvance of the science, there is no othercourse than to classify the subject-matter.Thus 'the carbohydrates' may be said tohave 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 ofview of a dominating theory, he found notonly that the material fell into systematic

order and grew rapidly under the stimulus

of fruitful investigation, but in turncontributed to the firmer establishment ofthe theoretical views to which the subjectowed its systematic new birth On theother hand, every chemist knows that it isonly the simpler of the carbohydrateswhich are so individualised as to beconnoted by a particular formula in thestereoisomeric system Leaving themonoses, there is even a doubt as to theconstitution of cane sugar; and theelements of uncertainty thicken as weapproach the question of the chemicalstructure of starch This unique product ofplant life has a literature of its own, andhow 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 particularreview of our work where we are taken totask for producing 'an aggravating book,inchoate in the highest degree .disfigured by an obscurity of dictionwhich must materially diminish itsusefulness' ['Nature,' 1897, p 241], theauthor, who is a well-known andcompetent critic, makes use of the shortexpression in regard to the more complexcarbohydrates, 'Above cane sugar, higher

in the series, all is chaos,' and in reference

to starch, 'the subject is still enshrouded inmystery.' This 'material' complexity is atits maximum with the most complexmembers of the series, which are thecelluloses, and we think accounts in partfor the impatience of our critic 'Obscurity

of diction' is a personal quantity, and we

must leave that criticism to the fates Wefind also that many workers whosepublications we notice in this present

volume quite ignore the plan of the work,

though they make use of its matter Wethink it necessary to restate this plan,which, we are satisfied, is systematic,and, in fact, inevitable Cellulose is in thefirst instance a structure, and the

anatomical relationships supply a certainbasis of classification Next, it is known

to us and is defined by the negativecharacteristics of resistance to hydrolyticactions and oxidations These are dealtwith in the order of their intensity Next

we have the more positive definition byultimate products of hydrolysis, so far asthey are known, which discloses moreparticularly the presence of a greater or

less proportion of furfural-yieldinggroups Putting all these together ascriteria of function and composition wefind they supply common or generaldividing lines, within which groups ofthese products are contained Theclassification is natural, and in that senseinevitable; and it not only groups thephysiological and chemical facts, but theindustrial also We do not propose toargue the question whether the latter addsany cogency to a scientific scheme Weare satisfied that it does, and we do notfind any necessity to exclude a particularset of phenomena from consideration,because they involve 'commercial' factors.

We have dealt with this classification inthe original work (p 78), and we discussits 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, anymore than a primary alcohol or analiphatic alcohol are the only alcohols.This point is confused or ignored inseveral of the recent contributions ofinvestigators It will suffice to cite one ofthese in illustration On p 16 we give anaccount of an investigation of the severalmethods of estimating cellulose, which isfull of valuable and interesting matter Thepurpose of the author's elaboratecomparative study is to decide which hasthe strongest claims to be regarded as the'standard' method They appear to have apreference for the method of Lange—viz.that of heating at high temperatures (180°)with alkaline hydrates, but the

investigation shows that (as we haddefinitely stated in our original work, p.214) this is subject to large and variableerrors The adverse judgment of theauthors, we may point out, is entirelydetermined on the question of aggregateweight or yield, and without reference tothe ultimate composition or constitution ofthe final product None of the availablecriteria are applied to the product todetermine whether it is a cellulose(anhydride) or a hydrate or a hydrolysedproduct After these alkali-fusionprocesses the method of chlorination isexperimentally reviewed and dismissedfor the reason that the product retainsfurfural-yielding groups, which is, fromour point of view, a particularrecommendation, i.e is evidence of the

selective action of the chlorine andsubsequent hydrolysis upon the lignonegroup As a matter of fact it is the onlymethod yet available for isolating thecellulose from a lignocellulose by atreatment which is quantitatively to beaccounted for in every detail of thereactions It does not yield a 'normal'cellulose, and this is the expressionwhich, in our opinion, the authors shouldhave used It should have been pointedout, moreover, that, as the cellulose isseparated from actual condensedcombination with the lignone groups, itmay be expected to be obtained in ahydrated form, and also not as ahomogeneous substance like the normalcotton cellulose The product is acellulose of the second group of the

classification Another point in thisinvestigation which we must criticise isthe ultimate selection of the Schulzemethod of prolonged maceration withnitric acid and a chlorate, followed bysuitable hydrolysis of the non-cellulosederivatives to soluble products Apartfrom its exceptional inconvenience,rendering it quite impracticable inlaboratories which are concerned with thevaluation of cellulosic raw materials forindustrial purposes, the attack of thereagent is complex and ill-defined Thiscriticism we would make general bypointing out that such processes quiteignore the specific characteristics of thenon-cellulose components of thecompound celluloses The second division

of the plan of our work was to define

these constituents by bringing together allthat had been established concerning them.These groups are widely divergent inchemical character, as are the compoundcelluloses in function in the plant.Consequently there is for each a specialmethod of attack, and it is a reversion topure empiricism to expect any onetreatment to act equally on thepectocelluloses, lignocelluloses, andcutocelluloses Processes of isolatingcellulose are really more strictly defined

as methods of selective and regulatedattack of the groups with which theyoccur, combined or mixed A chemistfamiliar with such types as rhea or ramie(pectocellulose), jute (lignocellulose),and raffia (cutocellulose) knows exactlythe specific treatment to apply to each for

isolating the cellulose, and must viewwith some surprise the appearance at thisdate of such 'universal prescriptions' asthe process in question.

The third division of our plan ofarrangement comprised the syntheticalderivatives of the celluloses, thesulphocarbonates first, as peculiarlycharacteristic, and then the esters, chieflythe acetates, benzoates, and nitrates Tothese, investigators appear to havedevoted but little attention, and thecontribution of new matter in the presentvolume is mainly the result of our ownresearches It will appear from this workthat an exhaustive study of the celluloseesters promises to assist very definitely inthe study of constitutional problems

This brings us to the fourth and, to thetheoretical chemist, the most importantaspect of the subject, the problem of theactual molecular structure of thecelluloses and compound celluloses It isherein we are of opinion that the subjectmakes a 'law unto itself.' If the constitution

of starch is shrouded in mystery and canonly be vaguely expressed by generalising

a complex mass of statistics of itssuccessive hydrolyses, we can only stillmore vaguely guess at the distance whichseparates us from a mental picture of thecellulose unit We endeavour to show byour later investigations that this problemmerges into that of the actual structure ofcellulose in the mass It is definitelyascertained that a change in the molecule,

or reacting unit, of a cellulose,

proportionately affects the structuralproperties of the derived compounds, bothsulphocarbonates and esters This is atleast an indication that the properties ofthe visible aggregates are directly related

to the actual configuration of the chemicalunits But it appears that we are barredfrom the present discussion of such aproblem in absence of any theory of thesolid state generally, but more particularly

of those forms of matter which aregrouped together as 'colloids.'

Cellulose is distinguished by its inherentconstructive functions, and these functionstake effect in the plastic or colloidalcondition of the substance Theseproperties are equally conspicuous in thesynthetical derivatives of the compound

Without reference, therefore, to furtherspeculations, and not deterred by anyapparent hopelessness of solving so large

a problem, it is clear that we have toexhaust this field by exact measurements

of all the constants which can be reduced

to numerical expression It is most likelythat the issue may conflict with some ofour current views of the molecular statewhich are largely drawn from a study ofthe relatively dissociated forms of matter.But such conflicts are only those ofenlargement, and we anticipate that allchemists look for an enlargement of themolecular horizon precisely in thoseregions where the forces of cell-lifemanifest themselves

T h e cellulose group has been further

differentiated by later investigations Thefibrous celluloses of which the typicalmembers receive important industrialapplications, graduate by insensible stagesinto the hemicelluloses which may beregarded as a well-established sub-group.

In considering their morphological andfunctional relationships it is evident thatthe graduation accords with their structureand the less permanent functions whichthey fulfil They are aggregates ofmonoses of the various types, chieflymannose, galactose, dextrose, &c., so far

as they have been investigated

Closely connected with this group are theconstituents of the tissues of fungi Therecent researches of Winterstein andGilson, which are noted in this present

volume, have established definitely thatthey contain a nitrogenous group inintimate combination with a carbohydratecomplex This group is closely related tochitin, yielding glucosamin and acetic acid

as products of ultimate hydrolysis Specialinterest attaches to these residues, as theyare in a sense intermediate productsbetween the great groups of thecarbohydrates and proteids (E Fischer,Ber 19, 1920), and their furtherinvestigation by physiological methodsmay be expected to disclose a geneticconnection

T h e lignocelluloses have been further

investigated Certain new types have beenadded, notably a soluble or 'pectic' formisolated from the juice of the white currant

(p 152), and the pith-like wood of theÆschynomene (p 135).

Further researches on the typical fibrouslignocellulose have given us a basis forcorrecting some of the conclusionsrecorded in our original work, and a study

of the esters has thrown some light on theconstitution of the complex (p 130)

Of importance also is the identification ofthe hydroxyfurfurals as constituents of thelignocelluloses generally, and the proofthat the characteristic colour-reactionswith phenols (phloroglucinol) may beascribed to the presence of thesecompounds (p 116)

T h e pectocelluloses have not been the

subject of systematic chemical

investigation, but the researches of Gilson('La Cristallisation de la Cellulose et laComposition Chimique de la MembraneCellulaire Végétale,' 'La Revue,' 'LaCellule,' i ix.) are an importantcontribution to the natural history ofcellulose, especially in relation to the'pectic' constituents of the parenchymatouscelluloses Indirectly also the researches

of Tollens on the 'pectins' havecontributed to the subject in correctingsome of the views which have had a text-book currency for a long period Theseare dealt with on p 151 The resultsestablish that the pectins are rather thesoluble hydrated form of cellulosicaggregates in which acid groups may berepresented; but such groups are not to beregarded as essentially characteristic of

this class of compounds.

Furfural-yielding Substances

(Furfuroids).—This group of plantproducts has been, by later investigations,more definitely and exclusively connectedwith the celluloses—i.e with the morepermanent of plant tissues From thecharacteristic property of yieldingfurfural, which they have in common withthe pentoses, they have been assumed to

be the anhydrides of these C5 sugars orpentosanes; but the direct evidence for thisassumption has been shown to be wanting

In regard to their origin the indirectevidences which have accumulated allpoint to their formation in the plant fromhexoses Of special interest, in itsbearings on this point, is the direct

transformation of levulose into furfuralderivatives, which takes place under theaction of condensing agents The mostcharacteristic is that produced by theaction of anhydrous hydrobromic acid inpresence of ether [Fenton], yielding abrommethyl furfural

C6H12O6 - 4H2O + HBr =

C5H3.O2.CH2Br

with a Br atom in the methyl group Theseresearches of Fenton's appear to us tohave the most obvious and direct bearingsupon the genetic relationships of the plant

furfuroids and not only per se To give

them their full significance we must recallthe 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 matière

première, is probably rather a general

reserve for the elaborating work of theplant If now the aldose groups tend topass over into the starch form,representing a temporary overflowproduct of the assimilating energy, itwould appear that the ketose or levulosegroups are preferentially used up in theelaboration of the permanent tissue Wemust also take into consideration theresearches of Lobry de Bruyn showing thelabile functions of the typical CO group inboth aldoses and hexoses, whence we mayconclude that in the plant-cell thetransition from dextrose to levulose is avery simple and often occurring process