The manufacture of paper: being a description of the various processes for the fabrication, coloring, and finishing of every kind of paper ...

Front matter

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0°.

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Preface

To tell the story of the manufacture of paper and describe concisely the processes employed in the various stages of paper-making, and give an account of all the known substances that have ever been used for the purposes for which we employ paper is by no means an easy task. At the present time, when books, newspapers, and other' periodicals are issued to the world in numbers almost beyond calculation, certainly no apology is due for a dissertation on the manufacture of paper, on the score of the lack of importance of that article.

The remarkable advance which has been made in the United States in all classes of manufactures during the past twenty years has excited alike the admiration and the envy of the civilized w^orld, but in no industry has greater progress been made than in the fabrication of paper. The great ingenuity and intelligence of our people, coupled with an abundance of all the raw materials used in paper-making, have aided in developing that industry in this country to proportions entirely unknown in any other country on the globe.

It was the writer's first intention to have devoted the book eutirely to a description of the " practical'' processes employed

IV PREFACE.

in paper-making in various parts of the world ; and to this eud he collected in the United States, Germany, France, Belgium, and Great Britain a large amount of so-called "practical information," But upon a reconsideration of the subject, and by the advice of some of the leading paper-makers in the United States and in Europe, he decided that the publication of such information would prove of little value to the paper trade, for the reason that paper-makers in the United States have little to learn from the paper manufacturers of Europe. The machinery and processes in use in Great Britain and on the continent of Europe are far behind those emplo3^ed in the United States, consequently the author determined that the book should be confined almost exclusively to a description of the machines and processes employed in the leading mills of this country. In order that such descriptions should not be too meagre the size of the volume has been materially enlarged over that at first contemplated. If American readers of the present volume complain that the author has described at length processes and machines which are already familiar to them through trade publications or otherwise, they should remember that such inventions are probably not so familiar to those engaged in paper-making in foreign countries whence a considerable proportion of the present edition of this book will go.

On account of the importance of the acid or bisulphite processes for making pulp from wood, etc., the author has given considerable space to a description of such processes, and while he thinks the apparatus employed in working these processes is much too cumbersome and expensive for general use, he could

PREFACE. V

not on that account orait a description of them ; nor should he be held accountable for the defects in such processes, the aim in view being to present a description of the state of the art as it exists at the present time.

It would, of course, be impossible, in a book the size of the present one, to describe all the processes and machines which, have been invented and used in paper-making in the United States ; but the lists of patents which this volume contains give reference to the number and date of nearly all the inventions which have been patented in the United States since the year 1790 to the end of the year 1885, and copies of all patents issued subsequent to the year 1866 can be obtained, upon application to the Commissioner of Patents, at a cost of twenty-five cents each. Patents issued prior to the year 1866 require to be copied in manuscript, and the cost of such copies depends upon the number of words contained in the patent.

CHAELES T. DAYIS.

AYashington, D. C, 1114 Pennsylvania Ave,, July 1, 1886.

CHAPTER I. The History of the Manufacture of Paper

PAGE

Alliance between the manufacture of paper and progress in civilization . 1 7

Materials belonging to the Mineral, Vegetable, and Animal Kingdoms used for records of human intelligence . . . . . . . .18

Cla,y and Terra-cotta used for bank notes, public records, etc., in Nineveh and Babylon; Histories of Chaldea, Babylonia, and Assyria found on clay tablets . . . . . . . . . . . .19

Terra-cotta tablets in the British Museum ; The history of Creation and of the Flood found on terra-cotta tablets ....... 20

Egyptian papyi-i in the British Museum ; Description of tlie three forms of writing used by the Egyptians, Hieroglyphic, Hieratic, and the Demotic 21

Characteristic differences of the works written with Hieratic and Demotic characters . . . . . . . . . . . .22

Form and size of the Egyptian papyri ; Depositories of cylindrical rolls of papyrus ; Introduction of papyrus among the Western nations aided by Alexander ; Description of papyi'us ....... 23

Papyrus superseded by cotton paper ; Leather used by the Israelites ; Probable invention of parchment ; Manufacture and present use of parchment ............. 24

Chinese use of the inner bark of the bamboo ; Origin of the word paper ; Modern materials used in the manufacture of paper; Other uses for paper than as a printing and writing material ..... 25

Uncertainty of the precise time of the introduction of modern paper ; Kewards offered by M. Miserman and the Royal Society of Sciences at Gottingen for oldest manuscripts written upon rag paper; Tract of Peter, Abbot of Cluny, A. D., 1122-50, giving the first mention of rag paper ............ 26

Paper from fibrous materials and cotton-wool made by the Chinese, in A. D. 152; Cotton paper and its manufacture made known to the AVestern world by the Arabs ; Materials used by the Chinese in manufacture of paper . . . . . . . . , . . . .27

Vlll CONTENTS.

PAGE

Various titles applied to cotton paper in the Middle Ages; Early use of cotton paper by the Arabians ; Remarks upon the existing samples of cotton-paper MSS. written in European cotintries . .... 28

Copies of statutes left by Empress Irene, in the eleventh or twelfth century; Use of paper among the Greeks; The oldest European documents on cotton paper ; Arabians introduce paper into Spain, in 704 . . 29

Valencia, Xativa, and Toledo, the primitive seats of cotton-paper industry in Europe; Introduction by the Crusaders, in 1189, of manufacture of cotton paper into France; Rapid development of the paper trade in France in the fourteenth century ........ 30

Superiority, during a long period, of French and Dutch papers ; Manufacture of paper in England ; First English paper patent .... 31

]\Ianufacturc of paper in Italy after the fall of the INIoorish power in Spain ;

Establishment of paper-mills in Germany ...... 32

Arabians, in Spain, the first to mix rags with cotton pulp ; First manufacture of linen paper in Europe ; Discussion by James Yates as to the period and manner of the invention of linen paper .... 33

Specimens of linen paper described by Gotthelf Fischer, and by Schwand-

Uncertainty of the circumstances which led to the invention of linen paper; Remark by the Arabian physician, AbdoUatiph, upon the sale of cloth found in the catacombs . . . . • . . . .35

Abundant testimony that Egypt supplied all Europe with papyrus until near the close of the eleventh century ; Introduction of cotton paper into Europe in the eleventh century . . . . . . . .36

Superior facilities of the Egyptians for improvement in manufacture of paper; Extract from Petrus Cluniacensis . . . . . .37

Linen paper proved to be an Eastern invention, and first introduced into Europe by the Saracens of Spain ; Papers with and without water-marks 39

Varieties of paper and water-marks serve as a guide to approximating the periods of undated documents ; Peculiarities of rag paper at diflierent periods of its manufacture ......... 40

Paper mills in Europe, in January, 1886 ; Enumeration of the countries in Europe according to their relative importance in paper manufacture ; Modern pajsei'-mills in Japan, India, and Australia .... 41

Comparative production of paper in Canada, South America, Cuba, and Mexico ; United States the greatest paper manufacturing country in the world ; Manufacture of paper in England ...... 42

Progress of j^nper manufacture impeded in the United States by industrial depressions, arising from financial complications ; First paper-mill in the American Colonies established by the efforts of "William Bradford, one of the earliest printers 43

CONTENTS. IX

PAGE

First paper-mill in the Colonies built by William Rlttenhiiysen (William Rittenhouse) on Paper Mill Run, near Philadelphia ; Ivy Mill, in Delaware County, Pa., built by Thomas Willcox, in 1727 ; Paper-mills in Massachusetts under an exclusive patent, in 1728 ..... 44

Difficulty of procuring suitable workmen causes the stoppage of the mill . 45

Paper-mill in Connecticut established by a State bounty in 17G8 ; Paper-mills in America at the commencement of the Revolution . . .46

Invention of making paper of large size, by N. L. Robert, of Essonnes, France ; French bounty to aid the inventor ; Transfer of the machine to England 47

English patent to John Gamble for. improvement of Robert's machine; Patent to Henry Fourdrinier for manufacturing paper of an indefinite length 48

History of the Fourdrinier machine ; Paper-mills in the United States in

1810 . . .49

Value of paper produced in the United States in 1810; Importation of rags, from Europe ; Development of American industry by the War of 1812; American patent system; Destruction of Patent-office by fire in 1836 50

American patents for manufacture of paper; John Dickinson's invention patented in England, in 1809 ; Mr. Canson's improvement of the Fourdrinier machine, in 1826 . . . • . . . . .51

U. S. patent to Thomas Gilpin, of Philadelphia, for paper-making machine, in 1816 ; Thomas Gilpin's mills on the Brandywine for the manufacture of wool, cotton, and paper ; Disastrous results to wool and cotton manufactures by English competition after the close of the Avar . . . .52

Paper cut from a continuous sheet sent by Thos. Gilpin to Philadelphia ; Poulson's "Daily Advertiser" the first publication printed upon it ; M. Carey & Son's Historical Atlas of l^avoisne, printed on paper made by T. Gilpin, in 1821. . 53

Loss of Thomas Giljjin's mills by a flood, in 1822 ; Destruction of the paper industry in Pennsylvania and Delaware by heavy importations of paper for want of proper protection; Tariff Act of April 26, 1816 ; Congressional use of paper imported from England and France .... 54

List of patents for paper manufacture issued by the United States, from 1820 to 1830 55

Encouragement to cylinder machines of American invention after 1822 ; Value of the machinery and paper-mill projDerty stated at the convention of paper-makers, in 1842 . . . . . . . . .56

Keller's invention for grinding wood for manufticture of pulp ; Henry Voelter's improvement of the pulp-machine, patented in the United States ; Prejudice against wood-paper overcome by stratagem in Boston , 57

Superiority of wood-paper for rapid printing ...... 58

X CONTENTS.

PAGE

Great improvements in manufacture of paper since I860 .... 59

Comparison of decades 1830-1840 and 1840-1850; Advance in price of paper between 1850-1855 60

Census returns of 1860 of paper-making; Paper as a substitute for cotton after the outbreak of the Civil War; Prices of paper in 18G2 . . 61

Decline in price of paper after 1865 ; Introduction of wood-pulp and large consumption of straw for newspaper ; New materials for manufacture of Manilla paper ; Large number of patents issued for paper-making from 1865 to 1885 ; Cheapening of paper production from 1870 to 1885 . . 62

Chapter II

Materials used for Paper — Micrographical Study of the Manufacture OF Paper — Cellulose — Determination of Cellulose — Recognition of Vegetable Fibres.

Micrographic study of the manufacture of paper ; Necessary qualities of fibres for paper-making ; Five classes of paper-making substances ; Cellulose an especially characteristic product of the vegetable kingdom . . 77 Hydrocellulose and oxycellulose, with their chemical characteristics . . 78 Determination of cellulose ; Miiller's processes for . . . . .79

Improvement by Bevan and Cross upon Miiller's processes ... 80

Recognition of vegetable fibres ; Filaments of cotton as shown by the microscope ; Distinguishing feature of cotton filament from all other vegetable fibres ............. 81

Linen or flax fibre as seen under the microscope ; Effects of caustic potash upon linen and cotton fibres ; Effects produced upon linen and cotton fibres and tissues by their immersion in oil . . . . . .82

Distinguishing properties of New Zealand flax, hemp-fibre, sizal, and jute

fibres 83,

Examining fibres under the microscope . . . . . . .84

CHAPTER IIL

Commercial Classifications of Papers-Sizes of Paper — Commercial Classifications of Paper-Making Materials.

Classifications of papers and boards in the markets of the United States . 85

Sizes of papers ; News ; Machine finished book, white and toned . . 86 Sized super calendered book, white and toned ; Colored cover papers ; Mii-

nillas ; Flat writings ; " Linen" bank-ledger papers .... 87 Commercial classifications of paper-making materials ; Rags ; Classifications

of rags as quoted in the markets of the United States and Great Britain . 88

CONTENTS. XI

PAGE

Classifications of rope, bagging and threads, shavings and old papers . . 90 Classifications of fibres, coir goods, gutta-percha. India-rubber, wastes, and

Classifications of straw-pulp and Esparto grass ; List of chemicals, clays,

minerals, rosins, etc., employed in paper-making . . ... .92

List of aniline dyes . . . . . , . . . , .93

CHAPTER IV. Manufacture of Paper by Hand

Condition of paper-making at the beginning of the present century ; Use

of hand-made writing paper in Europe ....... 94

Moulding of paper by hand ......... 95

Taking the paper from the mould, draining, sizing, and drying ... 96 Illustration of process for making paper by hand . . . . .97

Water-mark in hand-made papers ; Production of hand-made paper in the

United States and in Great Britain 98

CHAPTER V. Disinfecting Rags — Purchasing Rags

Quarantine regulations for disinfection of rags ; Disinfection with sulphurous acid, or by boiling under pressure ........ 99

Parker's and Blackman's ajiparatus for disinfecting rags and other fibrous substances while in the bale, illustrated with detailed description . .100

Beneficial results claimed by the patentees . . . . . .105

Purchasing rags ; Frauds'in baling of rags ; City and country rags ; Detection of moisture in rags ......... 107

Detection of jute in linen ; Destroying cotton in linen by use of concentrated sulphuric acid. . . . . . . . . . .108

Chapter VI

Sorting Rags — Sorting Waste Paper — Sorting or "Dry-Picking" Esparto — Machine for Facilitating the Sorting of Paper Stock.

Cleaning the dust, sand, and other matters from the rags before sorting ; Sorting according to fibre and color . . . . . . .109

Classification of rags according to fibre and color 5 Sorting waste paper . 110 Duty of sorters ; Testing of waste paper . . . . . . .111

XU CONTENTS.

PAGE

Sorting or "dry-picking" Esparto ; Dry-picking a term used in contradistinction to wet-picking . . . . . . . , . .112

Machine for facilitating the sorting of paper stock ; Apparatus of Robert and Walter Moorhouse, Philadelphia, illustrated with detailed description . . . . . . .. . . . .113

Chapter VII

Cutting Rags by Hand — Cutting Rags by Machinery — List of Patents FOR Rag Cutters and Dusters — Cutting Wood for Chemical Fibre — Treating Wood before Grinding — Voelter's Machine for Cutting or Grinding Wood — List of Patents for Wood-Grinders — Corn-Husk Cutter.

Cutting rags by hand ; Apparatus of Edgar D. Aldrich, of Pittafield, Massachusetts, illustrated with detailed description . . . . .117

Manner of cutting rugs by hand . . . . . . . .119

Precautions requisite in manufacture of fine paper . . . . .120

Taylor's machine for cutting rags, illustrated with detailed desci'iption . 122 Bauraann's rag-cutting machine, illustrated with detailed description . .130 Coburn's machine for cutting rags, etc., or materials containing metallic and

other substances, illustrated with detaih'd description . . . .133

Taylor's machine for separating metallic substances from paper stock, illustrated with detailed description . . . . . . . .139

Otlwr rag-cutting machines . . . . . . . . .142

Sizes of the cut rags ; List of patents for rag-cutters and dusters issued by the government of the United States of America from 1790 to 1885 inclusive . . . . . . . . . . . . . 143

Straw-cutters; Treatment of the straw ....... 144

Cutting wood for chemical fibre ; Treating wood before grinding . . 145 Process of George F. Cushman, of Burnet, Vermont, for disintegration of wood fibres . . . . . . . . . . . . 146

Voelter's machine for cutting or grinding wood and reducing it to pulp ;

Condition of wood grinding prior to Voelter's invention . . . 148

Illustration and detailed description of Voelter's apparatus . . . 150 Operation of Voelter's machine ........ 158

Nature, etc., of the pulp produced by Voelter's method; illustration and

detailed description of a plant for producing pulp by the Voelter process 164 List of patents for wood grinders issued by the Government of the United

States, from 1790 to 1885, inclusive 166

Corn husk cutter ; Apparatus of William A. AVright, illustrated with detailed description . . . . . . . . . .171

CONTENTS. XUl

CHAPTER VIII. Dusting Rags — Wet Dusting — Waste-Paper Duster and AVasher

PAGE

Dusting rags ; The operation as generally performed . . . .175

Dusters consisting of a revolving drum with loose or swinging arms ; Description of rag dusting machines in use in England, Belgium, and other parts of the Continent and in the United States ; Combination of the "devil" and duster . . . . . . . . . .176

The waste from dusting, etc. ; Mean waste in the dusting, according to Prouteaux ; Waste of rags from moisture, overhauling, cutting, and dusting 178

A machine for reducing the loss in cleaning cut rags ; Apparatus of J. B.

Hart and Emory H. Walker, illustrated with detailed description . .179

AVet dusting ; Combined washing or cleansing and boiling process ; Apparatus of AV. E. Newton, illustrated with detailed description . . .185

AVaste-paper duster and washer ; Apparatus of Hiram Allen and Lyman S. Mason, illustrated with detailed description . . • . .189

Combination of an automatic transferring device, with the dusting engine and pulping vat to avoid having a large pile of loose dry paper in the mill 193

Elevator for transferring loose papers into the circuit vat . . . .194

Temperature of the water in the pulping vat ; Use of solvent for dissolution of ink when printed pajjers are used . . . . . , .195

Transforming printed papers into clean, refined, and bleached pulp . .196

Preferable arrangement of the dusting engine with the pulping and washing vats ; Arrangement for tearing apart folded papers, pamphlets, etc., sorting and freeing from dust . . . . . . . .197

Illustration and detailed description of the machinery . . . .198

List of American patents for rag dusters ....... 202

Chapter IX

Boiling Rags — Stationary Boilers — Revolving Boilers — Treating Colored Rags — Boiling Waste Paper — Boiling Straw — Boiling Esparto — Boiling Manilla and Jute — Boiling AA''ood — Soda Recovery — Acid or Bisulphite Processes of Treating Wood^^List of Patents for Preparing Cellulose from AVood by the Acid or Bisulphite Processes — List of Patents for Digesters with Lead Linings — List of all American Patents for Digesters for Paper Pulp — Methods other than the Mechanical, Soda, and Bisulphite Processes for the Treatment of Wood.

Boiling rags ; Importance of intelligent care in boiling .... 203 Objects to be gained by boiling ; Alkaline substances employed in boiling;

XIV CONTENTS.

PAGE

Chemical substances; Illustration of spherical boiler used in Europe and

in the United States 204

Use of lime and soda in boilinor i-ags ....... 205

Solvent properties of water ; Pressure of steam for boiling rags ; Mixture of lime and soda ash .......... 206

Proportions of lime and soda used in Europe for boiling the various stuffs ;

Preparation of the milk of lime ........ 207

Introduction of soda-ash into the boiler ; Caustic soda employed in boiling the different classes of rags ......... 208

Stationary boilers ; Illustration and description of a stationary boiler much

used in Great Britain . 209

Revolving boilers . . . . . . . . . . .210

Boiler of George F. Wilson, illustrated with detailed description . .211 Improved strainer for the blow-off of paper stock boilers ; Illustration of an ordinary rotary boiler, with detailed description . . . . .215

Strainer invented by Benjamin F. Mullen, illustrated with detailed description 217

Treating colored rags ; Course practically pursued by paper manufacturers in preparing their paper stock ; Patented process of George F. AVilson and Philip O'lleilley, with illustration of apparatus and detailed description 219

Operation of preparing the stock ........ 221

Use of permanganate of potash, and of the soluble salt of manganese . 223

Boiling waste paper ; Extraction of writing ink ; Tubs used for boiling waste paper ............ 224

Proper mode of conducting the boiling operation ; Distribution of the soda-ash solution ; Covering the iron tubs with wood or asbestos to prevent the escape of heat ; Treatment of the liquor after each boiling . . 225 Profitable use of waste steam from the engine ; Properties of the latent heat of steam ; Distillation in vacuo at a low temperature effects no saving in fuel ; Treating waste paper so as to make paper entirely therefrom . 226 Process patented by J. T. Ryan ........ 227

Other methods of treating waste papers ....... 228

Boiling straw ; Mellier's process for treating straw ..... 229

Burns' s process for treating straw ; Illustrations and detailed description of Burns's vessel for boiling the straw ; Disintegrating machine, and stationary grinding disk. .......... 231

Boiling coal tar with the alkalies employed in treating straw . . .235 Other methods of treating straw ; Treatment of corn leaves and stalks of oat, barley, wheat, and rye straw . . . . . . . .236

Boiling esparto . 237

Statement showing the amount of caustic soda for boiling different varieties of esparto ............ 238

CONTENTS. XV

PAGE

Boiling Manilla and j lite ......... 239

Conley's process foi- boiling and bleaching jute ; Preparatory operations . 240 Equivalents for standards of caustic alkali ; Two points of prime importance in this process ; Advantages claimed for this process . . . 241 Other experiments in using jute in the manufacture of so-called white paper ; Boiling wood ; Chemically prepared wood-pulp ; Process of Sinclair and

of Houghton 242

DitRculties encountered in boiling chipped wood with caustic soda at a high temjDerature ; Use of bisulphite of lime, and of bisulphite of magnesia to prevent oxidation and weakening of the fibres ..... 243

Process patented by Dr. Mitscherlich, of Prussia, of preparing cellulose from wood ............ 244

Difficulty caused by the use of bisulphite ; Plan joroposed by Eitter and Kellner to overcome ... ... . . . . . 245

Objection to the cellulose obtained from wood by the acid processes ; Pure cellulose only obtained by exhaustion in an alkaline solution subsequent to the acid treatment ; Woods commonly used in the manufacture of "chemical wood-pulp;" Boiling with soda; Description of apparatus for cutting wood into chips ......... 246

Dahl's process of producing cellulose from wood, straw, esparto, or other vegetable matters, by boiling them under pressure in a hydrated solution containing sulphate of soda, carbonate of soda, soda hj-drate, and sodium

sulphide 249

Defects of boilers for digesting wood by the soda process .... 252

Marshall's boiler for digesting wood by the soda pi'ocess ; Illustrated with detailed description .......... 254

Soda recovery ; Illustration of a Porrion, evaporating, and incinerating oven

with detailed description 258

Acid or bisulphide process of treating wood; Graham's method of treating wood and other fibrous substances for the production of fibre, for paper-making, etc., by the injection of sulphurous acid, either alone or in combination with potash, soda, magnesia, lime, or other suitable base in the form of a solution containing an excess of acid, into a closed or open vessel, or digester, during the operation of boiling. .... 260

Mitscherlich' s processes of preparing cellulose from wood .... 263

Illustration and detailed description of Dr. Mitscherlich's apparatus . . 264

Operation of Dr. Mitscherlich's apparatus . . . . . .271

Francke's process of manufacturing paper-pulp from Avood, esparto, straw,

Francke's apparatus illustrated with detailed description . . . .277

Operation of Francke's apparatus ........ 285

Some of the defects of the acid or bisulphide process of treating wood . 289 PIctet and Brelaz's process of treating wood for conversion into paper-pulp, which consists in first subjecting the same to the action of a vacuum and

XVI CONTENTS.

PAGE

to that of a sursatiirated solution of sulphurous acid at a temperature not exceeding 212° F. . . . . . ... . . . 290

Marshall's boiler for treating wood for paper-pulp by the acid or bisulphide processes, illustrated with detailed description ..... 292

List of patents for preparing cellulose from wood by acid or bisulphide processes issued by the Government of the United States from 1790 to 1885 inclusive ; List of patents for digesters with lead linings to be used in the preparation of cellulose, issued by the Government of the United States from 1790 to 1885 inclusive 295

List of all patents for digesters for paper-pulp, issued by the Government of the United States, from 1790 to 1885 inclusive . . ' . . . 296

Methods other than the mechanical, soda, and bisulphite processes for the treatment of wood ; Aussedat's process of treating wood ; Description of the apparatus ........... 299

Machine for crushing wood invented and patented in France by Iwan

Koechlin 302

Description of the mills used in France by Mr. Aussedat . . . . 303

Eesults from experiments made at the Onnonay Laboratory with steam ; Experiments made to bleach the more or less reddish pulp with hydrochloric or azotic acids, and by fermentation of beer yeast . . . 304

Bachet-Machard process of disintegrating wood ..... 305

Eesults from the Bachet-Machard method ...... 306

Percentage yield of pulp from esparto, and straw, and pine wood ; Classification of the succedaneous pulps ; Treating wood with aqua regia ; Treating wood with ammonia, etc. . . . . . . .307

Chapter X

Washing Rags — Washing Waste Paper or " Imperfections" — Washing Straw — Washing Wood-Pulp — Washing and Pouching Esparto — Wash- Water — List of Patents for Pulp-AVashing and Straining.

Washing rags; Tlie Hollander rag engine ...... 309

Illustration and detailed description of the principal parts of the rag engine used in the United States . . . . . . . . .310

Approximate waste from washing, boiling, and reduction of the rags to half-stuff 316

Washing waste paper or " imjierfectlons" ; Stock designated as "imperfections" . 317

Difficult}' experienced in re-pulping clippings and scraps of paper . .319 Process of Cliarles Coon for repulping papei'-stock ..... 320

Ordinary method of bleaching , . . . . . . .322

Washing straw 323

CONTENTS. XVll

PAGE

Washing wood-pulp ; Treatment of mechanically-prepared and of chemicallyprepared wood-pulp . . . . . , . . . .324

Washing and "pouching" esparto ........ 325

Description of the poacher or " potching engine" . . . . . 326

List of American patents for washing engines ; Wash water . . .327

Composition and characteristics of pure water . . . . .328

Constituents of rain water and of spring water ..... 329

Constituents of river water ; Dr. Clark's soap test for hai-dness of water . 330 Determination of constituents and hardness of water; Qualitative examination of water as to its admixtures ........ 331

Danger of using apparatus containing chemical tests without a proper knowledge of chemistry ......... 332

A determination of hardness with alcoholic soap solution serves in most cases as a substitute for a quantitative analysis ; Distinction between ' ' total hardness," "permanent hardness," and "temporary hardness" . . 333 Standard soap solution ; Standard calcic chloride solution . . . 334

Clark's table of hardness ; Table of hardness in parts per 100,000 . . 335 Conversion of English degrees of hardness into German, and vice versa ;

Purification of water to be used in making best qualities of paper . .33 7

List of patents for pulp washing and straining issued by the government of the United States, from 1790 to 1885 inclusive . . . . . 338

CHAPTER XL

Bleaching Powder — Estijmation of Chlorine in Bleaching Powder — Preparing and Using the Bleaching Solution — Zinc Bleach Liquor- — Alumina Bleach Liquor — Draining— Sour Bleaching — Bleaching with Gas — Bleaching Pulp made from old Papers or Imperfections — Bleaching Straw — Bleaching Wood Fibre — Method for Bleaching Wood, Straw, etc. — Bleaching Jute — Bleaching of Materials composed of Hemp, Flax, etc. — Bleaching Vegetable Tissues with Permanganate of Potash— Bleaching Paper Pulp by applying the Bleaching Agent in a Sprayed Condition — Bleaching in Rotaries — List of Patents for Bleaching Pulp.