INDIA RUBBER, GUTTA-PERCHA, AND BALATA. INDIA RUBBER, GUTTA-PERCHA, AND BALATA-: Occurrence, Geographical Distribution, and Cultivation of Rubber Plants; Manner of Obtaining and Preparing the Raw Materials, Modes of Working and Utilizing Them, Including Washing, Loss in Washing, Maceration, Mixing, Vulcanizing, Rubber and Gutta-Percha Compounds, Utilization of Waste. Balata, and Statistics of Commerce. BY WILLIAM T. BRANNT, EDITOR OF " THE TECHNO-CHEMICAL RECEIPT BOOK.' ILLUSTRATED BY TWENTY-FOUR ENGRAVINGS. PHILADELPHIA : HENRY CAREY BAIRD & CO, INDUSTRIAL PUBLISHERS, BOOKSELLERS AND IMPORTERS, 810 WALNUT STREET. LONDON : SAMPSON LOW, MARSTON & CO, LIMITED, ST. DUNSTAN'S HOUSE, FETTER LANE, FLEET STREET. 1900. COPYRIGHT BY HENRY CAREY BAIRD & CO. 1900. PRINTED BY THE WICKERSHAM PRINTING COMPANY 53 and 55 North Queen Street, LANCASTER, PA., U. S. A. PREFACE. IT is scarcely necessary to enter upon the import- ance of the rubber industry, or of the great trade in rubber which has now developed with all countries supplying the raw material a trade which amounts to fully a million tons, worth more than $50,000,000 a year. Owing to the peculiar physical and chemical properties of rubber, gutta percha, and balata, the industrial applications of these materials, and com- pounds of them, are becoming more and more ex- tensive, and for some branches of industry, particu- larly electric engineering, they are indispensable. Although rubber and gutta percha have been worked on a large scale for scarcely fifty years, the industry has developed with remarkable rapidity, and there are now numerous large factories exclu- sively engaged in working these useful materials. The aim of this book is to give the reader a knowledge of the raw materials, as well as to pre- sent the industry in all its various branches as carried on by the most progressive manufacturers. (v) 82897 VI PREFACE. With this object in view all the available informa- tion has been brought together, and to make this information as complete and practical as possible the researches of the most eminent authorities have been consulted and drawn upon. The book has been provided with a copious table of contents and a very full index, which will render any subject in it easy and prompt of reference. \V. T. B. PHILADELPHIA, March 1, 1900. CONTENTS, I. INDIA RUBBER. CHAPTER I. RAW MATERIAL. PAGE India rubber a product of the plant organism ; Historical review ; Shape in which India rubber was first brought to Europe; La Condamine's discovery 1 Description, by Fresneau, of a tree yielding India rubber; Fuset-Aublet's journey to Guiana ; Researches of James Howison and of Roxburgh ; Description of a plant yielding milky juice, by Coffigny; Investigations of Herissant and Macquer 2 Priestley on the application of rubber ; Berniard's ex- periments; Faujas de St. Fond's investigations of mineral caoutchouc ; Foucroy, Berthollet and Gio- bert's studies of rubber; Grossart's invention; Efforts of Besson, Johnson and others to prepare water-proof garments . 3 ^Commencement of the actual rubber industry; Nadier's invention; Use of benzine by Charles Mackintosh for dissolving lubber; Thomas Hancock's investigations; Invention which established the permanency of the rubber industry 4 Luedersdorf's observations; Goodyear's discovery of the process of vulcanizing rubber 5 First introduction of vulcanized rubber shoes; Hancock's process of vulcanization; Parke's process; Augustin G. Day's improved method; Girard's process; Goodyear's invention uf hard rubber: Hancock's invention of man- ufacturing rubber articles in moulds 6 (vii) Vlll CONTENTS. PAGE Occurrence of India rubber; Rubber contained in the milky juice of milk-weed: Habitat of the actual rub- ber-yielding plants; Properties of the milky juice or latex of rubber plants 7 Composition of the best quality of latex; arrangement of the rubber plants in four families ; EUPHORBIACE^K : Hevea; Micranda 8 Manioc or manihot (Plum Adams); Euphorbia; ULMA- CE^;; Castilloa; Ficus 9 Use of Ficus elastica as an ornamental plant ; Artocar- pus; Cecropia; APOCYNACE^E; Vahea 10 Landolphia; Urceola; Hancornia; Cameraria (Muller), Paramerio, (Benth); Leucomotis (Jack) . 11 Ahtonia (0.); Chanemorphia (G.); ASCLEPIADE.*;; Cy- nanchum (L.); Periploca Graeca (Z/.)l Callatropis pro- cera (R. Br.); On what the quality and quantity of j milky juice depend; Age at which trees may be tapped 12 * Arrangement of rubber plants into geographical groups ; Soil required for rubber plants , 13 Cultivation of rubber plants; First experiments in India with the native Ficus . .- . . 14 Experiments with Urceola elastica, U. esculcnta, and Cas- tilloa elastica ; Robert Cross' journeys to Central Amer- ica and the Amazon River ; Cultivation of rubber plants in the Kew Botanical Garden 15 Requirements of a country for the rational cultivation of rubber; Unsuitability of the territory of Assam; Ac- climatizing experiments with Manihot glaziovii. . . 16 Mode of preparing the seed, and of planting ; Formation of plantation by cuttings 17 Cultivation of Manihot in Ceylon; Cultivation of the Para rubber tree in Ceylon 18 Propagation by cuttings; Mode of planting 19 Age at which the trees may be tapped ; Cultivation of rubber trees in the French colonies ; Experiments at the botanical garden at Libreville 20 Report of E. Pierre; Carelessness of the natives in hand- ling young plants 21 Acclimatizing experiments in Cochin-China; Cultivation CONTENTS. IX PAGE of rubber trees in Central America; Suitability of some portions of Mexico for that purpose; Castilloa elastica and its occurrence in Mexico 22 Gathering and preparing the seed; Planting 24 Forest system of planting; Starting a regular plantation in regular orchard form 25 Setting out the plants; Protection of the young plants . 26 Xursery for young plants ; Transplanting the young plants 27 Mode of setting the plants in Chiapas and Tabasco ... 28 Cost of establishing a rubber plantation; Manner of ob- taining crude rubber ; Methods of obtaining milky juice; Cutting down the trees for this purpose .... 29 When cutting down the trees is permissible; Tapping the trees for obtaining the milky juice; Method employed on the lower Amazon river; Tools used by the collector; Mode of making the incisions 30 Manner of collecting the milky juice ; Average yield ; Quantity of sap obtained from each tapping of 150 trees 31 Modes of tapping on the Upper Amazon, Central Amer- ica, Africa and Asia 32 Methods in use in Australia; Coagulation of the latex . 33 Methods by \\hich coagulation is effected; By artificial heat; By natural heat; By skimming; By disintegra- tion 34 By natural or artificial heat in combination with chemi- cal disintegration; Description of the various processes of coagulation : Coagulation by artificial dry heat or fumigation ; Preparation. of Para rubber 35 Fumigation '.. 36 Ellicacy of the fumigating process; Composition of the milky juice of Hecea and of Micranda 37 Fumigation a simple means of rendering substances sub- ject to putrefaction or fermentation innocuous ; Grand- jean and AVasers experiment in coagulation 38 Preparation of some kinds of Para rubber of less fine quality . . 39 Para entrefina; Sernamby or niggerhead; Coagulation of the latex by means of riioist artificial heat or by boil- ing; Method in use by the Indians of Mexico 40 X CONTENTS. PA8B Defects of this process; Preparation of rubber from the latex of Castilloa in Mexico ; Coagulation of the latex by natural heat the soil as a means of separating water; Use of this method in Africa 41 Method employed by some tribes on the Congo and in Angola; Coagulation by natural heat, evaporation upon the human body 42 Use of this method by the natives of East Africa and by some tribes in Angola; Coagulation by natural heat evaporation upon other even surfaces than the ground 43 Mode of conducting the operation in Ceara; Ceara scraps 44 Ceara rubber and its properties; Improvement in the method of collecting the latex of Manihot 45 Habitat of Manihot; Coagulation by skimming after the addition of the same quantity of water, and a shorter or longer rest; Methods employed in Bahia, Nicaragua, Central America and Assam 46 Coagulation by rest after the addition of four to five times the quantity of water; R. P. Merlon's descrip- tion of the method employed on the Congo for treat- ing the latex of Landolphia 47 Variety of rubber known as " thimbles ;" Defects in the method of its preparation; Chemical disintegration by mineral reagents 48 Coagulation by alum; Strauss' process; Objections to this process 49 Coagulation by sulphuric acid and sea salt; Coagulation by soap water . 50 Description of this process by E. Bard; Experiments of Dr. Morisse in treating the latex of Hevea 51 Results of experiments in coagulation with various agents 52 Most effective solutions 53 Rousseau's conclusions regarding the various methods of coagulation .... 54 Chemical disintegration by the addition of vegetable agents; Morellet's conclusions from the examination of Madagascar rubber; Cousin's experiments .... 55 Treatment of the latex of Castilloa in Guatemala and CONTENTS. XI PAGE Nicaragua; Coagulation by a combination of natural or artificial heat with chemical disintegration: Method employed with Vahea and other climbing plants ... 56 Summary of the results of experience and experiments in coagulation 58 Chemical and physical properties of crude rubber; Properties of the fresh latex of Hevea . 60 Chemical composition of the latex of Hevea brasiliensis; Variations in the properties of crude rubber; Compo- sition of crude rubber 61 Bodies soluble in alcohol contained in crude rubber; Chemical change in the substance of rubber produced by light 62 Effect of air on crude rubber; Gradual oxidation of rub- ber; Content of water in good rubber 63 Decrease of content of carbon in rubber; Effect of water on rubber; Behavior of rubber towards sulphur. 64 Vulcanized rubber; Hard rubber or ebonite; Behavior of rubber towards solvents 65 Substances capable of dissolving rubber in the actual sense of the word ; Results of experiments as to the solubility of different varieties of rubber 66 Method for effecting a complete solution of rubber . . 67 Objection to the use of carbon disulphide as a solvent; Mode of freeing oil of turpentine from water .... 68 Solution of rubber in heated linseed oil; Caoutchoucine or oil of caoutchouc; Most suitable solvents for prac- tical purposes; Preparation of absolute alcohol ... 69 Preparation of rubber and gutta-percha solutions accord- ing to C. Fry's patented method . . 70 Behavior of rubber in heat; Composition of crude oil of caoutchouc; Composition of isoprene, caoutchene, and heveene 71 Bodies determined as being present in oil of caoutchouc; Yield of isoprene, caoutchene and heveene from 11 Ibs. of fresh Para rubber 72 Most effective solvents among the products of distilla- tion; Commercial rubber; Arrangement of the vari- eties of crude rubber in three principal classes .... 78 Xll CONTENTS. PAGE Summary of the best known varieties, including their commercial names, place of origin, form in which they are brought into commerce, appearance, properties, etc.; AMERICAN RUBBER: South America; Fine Para, Seringa fina, Borracha or Jebe; Entrefine Para, i fine Para, Grossa 74 Nigger heads, Para Sernamby, Sernamby de Borracha, Sernamby de Jebe, Cabecja de negro; Virgin sheets or Mattogrosso Para (Para blanc); Ceara scraps .... 75 Pernambuco (Mongabeira); Maranham; Bahia ..... 76 Carthagena (Esquebo); Cuidad-Bolivar, Columbia Vir- gen; Cayenne; Peru in slabs or caucho 77 Peruvian balls, Sernamby de Perou, Seramby de Caucho; Guayaquil; Central America: Colon and Panama; Mexican and other Central America and West Indies sheets 78 Guatemala; Nicaragua. Mexico, Ecuador and West Indian scraps; AFRICAN RUBBER; Senegal and Bissao balls. 79 Gambia balls; Casamanza (Boalam); Casamanza (Gam- bia) 80 Sierra Leone Niggers; Massai Niggers; Sierra Leone twist; Liberia; Grand Bassam; Accrah 81 Niger Niggers; Gaboon Balls; Gaboon Tongues; Kassai rouge; Kassai noir 82 Kassai noir in balls; Kassai strips; Upper Congo (com- mon); L r pper Congo (white); Equator; Lopari; Busira; Aruwinri, Mongala, Buinba: Uelle 83 Lower Congo (thimbles); Luvituku: Loanda thimbles; Loanda Niggers 84 Angola Niggers or Nigger-heads; Benguela Niggers; Mozambique Balls 85 Mozambique Spindles; Madagascar, black; Madagascar, pinky; Madagascar Niggers: ASIATIC RUBBER; Assam 86 Rangoon; Penang; Ceylon; Java and Padong 87 Borneo; Borneo Djambes; Borneo (Ben Koclen); AUS- TRALIAN RUBBER; New Caledonia; Statistics ... 88 Estimate of the world's production and consumption of rubber; Principal market for crude rubber in Europe; (Quantity of rubber imported by Liverpool 89 CONTENTS. Xlll PAGE Importation by London and the principal European countries together with the United States 90 Prices of India rubber 91 CHAPTER II. MECHANICAL TREATMENT OF CRUDE RUBBER. Removal of the various impurities present in the crude material; Admixtures found in crude rubber .... 92 Manipulation required by the different varieties of rub- ber; Softening or superficial washing; Cutting up . . 98 Cutting machine, illustrated "and described 94 Rolling or washing; Washing machine, illustrated and described 95 Use of hollow rolls 97 Drying 98 Table showing loss of weight by washing and drying ; Further working of the washed crude rubber .... 99 Masticating and mixing machine; illustrated and de- scribed 100 Variation in the treatment of crude rubber 101 Fine-cut sheets; Methods for obtaining blocks of rubber; Manner of cutting up the blocks 102 Scale of commercial thickness of fine-cut sheets; Inven- tion of the manufacture of fine cut sheets by Charles Mackintosh 103 Adulteration of fine-cut sheet; Cutting square threads from pressed blocks ; Preparation of mixed mass from washed crude rubber 104 Nature of the admixtures; Manipulation of kneading and mixing 105 Mixing machines 106 Calender, described and illustrated 107 CHAPTER III. VULCANIZ ATION. Characteristic peculiarities of crude non-vulcanized rub- ber; How vulcanization is effected; Experiments of Anselme Payen 109 XIV CONTENTS. PAGE Various modes of vulcanization; Cold vulcanization, in- vented by Parkes 110 Uses to which cold vulcanization is applied Ill Preparation of dichloride of sulphur 112 Apparatus for the preparation of dichloride of sulphur, described and illustrated ; Properties of dichloride of sulphur 113 Preparation of anhydrous petroleum; Warm vulcaniza- tion, invented by Hancock 114 Girard's process of vulcanization; Preparation of penta- sulphide of potassium 115 Advantage of Girard's process lltt Another process of vulcanization; Mechanical combina- tion of rubber with sulphur; Goodyear's process . . . 117 Vulcanizing operation 118 Difference of opinion as to the degree of heat required for vulcanization; Reasons for this difference in opinion; Vulcanization the most difficult and critical operation in the manufacture of rubber goods 119 Limit of temperature in which vulcanization will pro- gress in a correct manner; Conditions on which the temperature for vulcanizing depends 120 Vulcanizing apparatus ; Brick chambers heated by hot air; Vulcanizing heaters and presses; Ordinary steam heater, described and illustrated 121 Vulcanizing press, described and illustrated 123 Press heated by petroleum, described and illustrated . . 124 Vulcanizing operation ; Mechanical treatment of the articles; Vulcanizing articles in moulds; Vulcanizing hose; Metals for moulds 125 Preventing the articles from sticking to the moulds; Pre- venting thick sheets from warping; Sorting the articles before heating ; Vulcanizing in two operations . . 12<> Modification of the vulcanizing process; Process for arti- cles requiring only light treatment; Vulcanization of articles treated with saturated solution of sulphur in carbon disulphide ... .... 127 Vulcanization with an addition of pentasulphide of anti mony; Difference in the action of commercial penta sulphide of antimony; Turner's process 128 CONTENTS. XV CHAPTER IV. RUBBER COMPOUNDS. PAUE Substances used as admixtures; Coloring matters . . . 129 Coloring by the production of chemical combinations in the mass; Receipts for black, green and violet .... 130 Admixtures for rubber compounds which require to be rough; Addition of black pitch for cheap products . . 131 White rubber masses: Cheap rubber masses, with an ad- dition of resin 132 Metalized rubber; Preparation of vulcanized rubber, which does not swell up when brought in contact with fat; To make rubber pervious to perspiration; Gerner's method of mixing rubber and gutta percha with cam- phor, cowrie copal, mustard or hemp seed, freed from oil 133 Kamptulicon and its manufacture 134 Uses of kamptulicon; Coloring of kamptulicon 135 Rubber leather, and its manufacture 136 Balenite. or artificial whalebone 137 Plastite, and its manufacture 138 Formula for plastite mass; Grinding and polishing com- positions; Substances suitable for the purpose .... 139 Formulas for sharpening and polishing compositions . . 140 Preparation of polishing and grinding compositions. . . 141 Rubber enamel and its preparation 142 Preparation of colored enamel 143 Manner of applying the enamel; Deodorizing vulcanized rubber 144 Various processes of deodorizing vulcanized rubber . . . 145 Desulphurized vulcanized rubber; Method of desulphur- izing 146 Superiority of vulcanized rubber from which the excess of free sulphur has been removed. 147 CHAPTER V. HARD RUBBER. Principles upon which the preparation of hard rubber is based; Zinc compound recommended by Goodyear . . 148 Substances used as admixtures; Uses of hard rubber; XVI CONTENTS. PAGE Marnier of combining the rubber, sulphur and other ingredients 149 Engel's method of rilling the moulds; Vulcanizing hard rubber 150 Coloring hard rubber; Dusting and plating, or enamel- ing; Method of dusting 152 Process of plating or enameling; Admixture of indiffer- ent substances 153 Coloring substances; 'Utilization of waste 154 Formulas for the composition of hard rubber; Ebermay- er's examination of hard rubber combs 155 Formula for hard rubber possessing great hardness and solidity, with but little elasticity; Effect of an admix- ture of shellac on hard rubber; Formula for a compo- sition with shellac ... 156 Newton's mixture for buttons, knife handles, etc.; John- son's compound for brushes, curry combs, etc.; Use of hard rubber in the manufacture of black ornaments . 157 Physical and chemical properties of hard rubber. . . . 158 Preparation of artificial ivory 159 Decolorizing and bleaching rubber 160 Treatment with chlorine, and apparatus used for this purpose, described and illustrated 161 American process of bleaching rubber; Simplest method of bleaching 163 Further treatment of the bleached mass; Incorporation of different substances with the plastic mass 164 Different ways of working the colored masses; American receipt for artificial ivory 165 CHAPTER VI. MANUFACTURE OF ARTICLES FROM SOFT RUBBER. Articles made from fine cut sheets and their manu- facture " 167 Rubber toys 168 Rubber balls; Hollow articles 169 Moulds of more than one piece; Acceleration of the evaporation of the solvent; Mixing sulphur with the rubber dough 170 CONTENTS. XV 11 PAGE Preparation of small solid balls of vulcanized rubber; Manufacture of small toy balloons 171 Printing rolls for use in dye works; Letellier and Ver- straat's process of making the rubber jacket of the pressure rolls of cloth printing machines 172 Preparation of rubber threads; Square cords from crude rubber 173 Machine for cutting these cords 174 Simplest manner of cutting bands into threads; Thread cutting machine 175 Cutting square cords from prepared rubber 176 Round rubber threads; Aubert and Gerard's process . . 177 Diameter of threads which can be prepared by pressing; Preparation of thinner threads; Rubber hose .... 179 Hose or tubing for chemists' use; Kinking of hose; Manufacture of ordinary rubber hose 180 Cores used; Manufacture of short tubing; Hose of greater length or larger diameter 181 Rubber hose with intermediate layers or stiffeners; Hose , with layers of wire; Small hose 182 Tubing machine manufactured by John Royle and Sons, of Paterson, N. J., described and illustrated .... 183 "Rubber sponge or moss rubber 188 Deodorizing rubber sponges; Rubber shoes 189 Bicycle tires; Classes of pneumatic tires 190 Single tube tires; Classes of compound tires; Dunlop tire 191 Morgan and Wright type of tire; Manufacture of water- proof tissues; First use of rubber for this purpose by Chas. Mackintosh ; Experiments to improve Mackin- tosh's process 192 Dumas' suggestion for the preparation of very thin sheets; First improvement in Mackintosh's process . . 193 Character of the tissues to be waterproofed; Preference for closely woven fabrics; Principal requisite of ma- terials 194 Preparation of fabrics of cloth and vulcanized rubber . 195 Method recommended by Johnson 196 Difficulties met with in the use of solutions; Advan- tages of using rubber compounds 197 XV111 CONTENTS. PAGE Rubber spreader, described and illustrated 198 Application of the solution by means of ladles; Protec- tion of the workmen from the evil effects of the vapors. 200 Apparatus for this purpose, described and illustrated . . 201 Mode of operating the apparatus; Best plan of arranging the work 2<)2 Tissues with an intermediate layer of rubber; Apparatus for this purpose, described and illustrated 203 Deodorizing water-proof fabrics 204 Use of saturated steam for this purpose 205 Manufacture of water-proof fabrics by means of rubber compounds; Preparation of compounds with linseed oil. 206 Properties of prepared linseed oil; Dissolving the rubber; Application of the solution; Manufacture of rubber shoes from fabrics water-proofed by means of rubber compounds 207 Rubber felt, felt paper, or Clark's patent felt 208 Fabrication of elastic webbings 209 Mode of stretching threads to be used for webbing; Weaving of rubber threads 210 Another method of preparing elastic webbings; Use of vulcanized threads 211 Recovery of solvents; 0. A. Burghardt's condensing ap- paratus, described and illustrated 212 CHAPTER VII. RUBBER VARNISHES AND LACQUERS. Preparation of rubber solutions 214 Precautions to be observed in the use of carbon disul- phide and of benzene; Increase in the dissolving power of fluids by heat 215 Apparatus for kneading rubber solutions, described and illustrated 216 Receipts for rubber varnishes; Leather lacquer .... 218 Varnish for gilders; Varnish for glass; Slow drying var- nish; Varnish for morocco 219 Flexible varnish; Water-proof coating for shoes and boots; Solution for repairing rubber shoes; Marine glue 220 CONTENTS. XIX PAGE Marine glue for damp walls 221 Jeffery's marine glue; Transparent cement for glass; Hard rubber lacquer 222 II. GUTTA PERCHA. CHAPTER VIII. RAW MATERIAL. Historical review ; Gutta-percha first brought to Europe by John Tradescant 224 Observations of Dr. Wm. Montgomery regarding gutta- percha, and his report on the subject to the Medical Board at Calcutta 225 Experiments by English manufacturers with gutta- percha; First patent for the utilization of gutta-percha granted to Alexandre, Cabriot and Duclos; Attempts to use gutta-percha for articles formerly made of rubber 226 Use of gutta-percha as an insulating material; First tel- egraph lines insulated with gutta-percha constructed by Werner Siemens; Wheatstone's idea of connecting England by telegraph with the Continent; First con- struction of a submarine cable by Walter Breit; Occur- rence of gutta-percha; Plants yielding gutta-percha 227 Dichopsis gutta or Isonandra gutta or Palagium gutta; Dichopsis oblong if olium 228 Dichopsis calophylla (Benth. and Hook.); Dichopsis selendit; Dichopsis Krantziana; Dichopsis pustulatum; Payena Lerii; Bassia Parkii; Mimusops 229 Geographical distribution of trees producing gutta percha; Manner of obtaining crude gutta percha; Time of collection; Tools used in cutting down the trees . . 280 Various ways of preparing gutta percha, as observed by Leon Brasse and Seligmann-Lui 231 Scarcity of unmixed gutta percha ... 232 Variations in the statements regarding the yield of crude gutta percha; Danger of the entire exhaustion of the sources . . . 233 XX CONTENTS. E. Jungfleisch's experiments in extracting gutta percha from all parts of the tree; Method of extraction . . . 284 Commercial guttapercba; Diversity in the condition of the crude product; Mode of assorting and classifying gutta percha by the Chinese ; Summary of the best known varieties of gutta percha, including their com- mercial names, place of origin, form in which they are brought into commerce, appearance, properties, etc.; Pahang 2o(> Sandakan; Maragula; Bagan 2^7 Banjer-massin; Kotaringin; Pekang: Sarawak 238 Pontianak; Pedang; Sarapong or Sauni 239 Siak; Bolungan . . . 240 Cote; Cotonan; Kelatan 241 Pahang- white; Assahan; Tringanon 242 Boula-Balam ; Statistics; Quantity of gutta percha brought to Singapore, 1885 to 1896, calculated by Dr. E. Obach 243 Table showing the quantities imported direct from Sing- apore into the various countries ; Table showing re- export from England 244 Table showing countries which received the re-export from England 24-"> CHAPTER IX. CHEMICAL AND PHYSICAL PROPERTIES OF GUTTA-PERCHA. Properties of pure gutta percha 246 Specific gravity; Pliability; Behavior in the cold . . . . 247 Appearance of thin sections under the microscope; Be- havior towards solvents 248 Chemical composition of gutta percha 249 Payeifs examination of gutta percha; Properties of pure gutta, albane and fluavile 2>50 Relation between gutta, albane and iluavile; Other com- binations found in crude gutta percha; Clark's experi- ments upon gutta percha, interpreted by W. A. Miller 2ol Examination of cables which had been submerged for various periods; Chemical indifference of gutta percha: Behavior towards'acids 2">,s CONTENTS. XXI CHAPTER X. TREATMENT OF CRUDE C4UTTA PERCHA. PAGE Examination of the condition of the crude material; Re- moval of stones and apparatus for this purpose .... 255 Cutting up gutta percha: Drum slicing machine; Wheel cutting machine 256 Separation of the heavy admixtures; Washing machine, described and illustrated .... 257 Kneading machine; described and illustrated 258 Kneading machines with horizontal rolls, described and illustrated 259 Manipulation in the press or strainer; Preparation of the cleansed material for storage ... 260 Rolling the gutta percha into sheets, and machine used for this purpose, described and illustrated; Mixture of different varieties of gutta percha 261 Loss in washing and kneading 262 CHAPTER XI. INDUSTRIAL APPLICATION OF GUTTA PERCHA. Principal uses of gutta percha 263 Moulding articles from gutta percha; Gutta percha hose; Machine used for this purpose 264 Mode of operation 265 Machines for the manufacture of hose of any desired length 26H Modification of the press used for the manufacture of hose for preparing solid articles ; Gutta-percha threads 267 Apparatus for preparing threads . . 268 Manufacture of threads by rolling; Coating wires with gutta percha. 269 Insulation of telegraph wires; Manufacture of telegraph cables; Apparatus for coating wire with gutta percha, described and illustrated 270 Further protection of the cable 272 Machine for insulating electric wire and cables, manu- factured by John Royle & Sons. Patterson, N. J., de- scribed and illustrated . 273 XX11 CONTENTS. I'Aiil-: Vulcanization of gutta percha; Mixture recommended for the purpose 27i> Process of vulcanizing gutta percha with chloride of sul- phur 277 CHAPTER XII. BLEACHING OF GUTTA PERCHA GUTTA PERCHA COMPOUNDS. Bleaching agents used; Bleaching with chloroform. . . 278 Process for obtaining an entirely decolorized, pure white product; Apparatus for this purpose, described and illustrated 27', Cattell's bleached gutta percha 281 Gutta percha compounds; Use of compounds of rubber and gutta percha in galvanoplasty; Gutta purcha sheets for taking impressions of coins, medals, etc. . . 282 Mixture of rubber and gutta percha for overlapping ma- trices or moulds; Gutta percha and rubber compounds for machine belts; Formula of a compound for this purpose .... 283 Manufacture of belts 2S4 Hard gutta percha compounds; Materials used for white and colored articles; Total weight of the materials added 2.sf> Methods of disguising the odor of gutta percha; Corn- pound of gutta purcha and wood . 286 Sorel's gutta percha compounds; Formula for the best of Sorel's compounds ; Manner of preparing the com- position 27 Unger's directions for examining articles vulcanized with pentasulphide of antimony; Determination of sulphur 298 Henriques' method 299 Determination of antimony; Determination of calcium . 300 Results obtained by Unger in examining a sample of rubber 301 Determination of other mineral filling substances; De- tection of admixtures of organic substances; Henriques' method of detecting a content of oily substitutes . . 302 III. BALATA. CHAPTER XV. HISTORY, OCCURRENCE AND USES OF BALATA. Balata made known, in 1857, by Prof. Bleekrode; Speci- mens forwarded to the Kew Museum ........ 303 Distribution of the genus Mimusops; Habitat of trees yielding balata; Mimusops Balata 304 XXIV CONTENTS. PAGE Varieties of Mimusops which yield balata; Mode of col- lecting balata in Venezuela 305 Methods of collecting balata in Dutch Guiana and in British Guiana 30(i Properties of crude balata; Impurities in the com- mercial article; Great value of balata from Mimusojix JJalata and M. globosa 307 Table showing price and export of balata from British and Dutch Guiana 308 Principle difference between gutta-percha and balata . 309 Manner of working crude balata 310 Uses of unmixed balata; Manufacture of balata machine belts; Joining the ends of belts, described and illus- trated 311 Index . . 314 UlN ^ TY INDIA RUBBER, -GOTTA PIRCHA, BALATA. I. INDIA RUBBER. CHAPTER I. RAW MATERIAL. INDIA RUBBER, or caoutchouc,* is a product of the plant organism. Together with other solid and liquid bodies, it is very likely formed as a milky fluid in separate vessels by the conversion of tissue- mass, and, on the juice drying up, remains behind with other solid substances present. According to some botanists, it is a never-wanting constituent of every vegetable milky juice, occurring also in opium. The commercial article, however, is ob- tained from various trees of the tropical and semi- tropical regions. Historical Review. India rubber in the shape of bags and bottles was first brought to Europe in the commencement of the eighteenth century, but neither its nature nor origin was known. In 1735, La Condamine first Latin, gummi elasticum ; German, gum/mi; French, ; Spanish, seringa; Portuguese, xirringa. (i) 2 INDIA RUBBER, GUTTA PERCHA, BALATA. discovered that the substance was the dried milky juice of a tree, which the Indians on the coast of the Amazon River called Caout-Chou, and from which, from time immemorial, they had been making water-proof fabrics, shoes, vessels, etc. Fresneau, who had settled in Cayenne, described, in 1751, a tree yielding India rubber, and to thia indefatigable ex- plorer we are indebted for the first exact description of the method employed by the natives for obtain- ing it. The researches of La Condamine and Fres- neau caused the French botanist Fuset-Aublet to make, in 1756, a journey to Guiana. Two years later he published his work on the Flora of Guiana, in which he described the rubber tree, and applied to it the name Hevea guyanensis. James Ilowison, a physician residing in Prince of Wales Island, an island of the Malay Archipelago, first determined the species yielding an " elastic gum wine," and Roxburgh later on applied the name Urceola elastica to this species. The latter also discovered in Assam, in the forest on the shores of the Brahmapootra, the Ficus elastica. Finally Coffigny described a vine- like plant of Madagascar belonging to the jasmine family, which also yields a milky juice. When dried this juice forms an elastic resin resembling rubber. While the botanists studied the rubber-yielding plants, the chemists investigated the new resin, and succeeded in dissolving it. In 1768, Herissant and Macquer communicated simultaneously to the Paris Academy the results of their investigations, RAW MATERIAL. o and called attention to the fact that india rubber, which is insoluble in water and alcohol, may be softened and even dissolved in oil of turpentine and pure ether. At the same time they proposed the employment of the softened resin for the manu- facture of surgeons' probes and small tubes for use in the laboratory. The celebrated English chemist Priestley, in 1770, called the attention of scientists to the useful application of india rubber by recom- mending it for effacing lead-pencil marks. The experiments of the French chemist Berniard (1780) completed the labors of Herissant and Macquer, and foreshadowed the many uses to which india rubber might be applied in the future. Faujas de St. Fond occupied himself in the investigation of a kind of resin found in the mines at Castelton, and called it mineral caoutchouc. Foucroy, Berthollet and Giobert also w r ere interested in the study of india rubber. Grossart invented the most simple process of making from bottles of Brazilian rubber, tubes and other articles for physical and surgical purposes, as well as for household use. For the preparation of small tubes, he cut the bottles into strips of suitable size, softened them by placing them for half an hour in ether, or somewhat longer in volatile oil, rolled the strips upon a mandrel, and pressed them strongly by means of a rope wound spirally around them. On drying, the surfaces adhered together, and the pieces retained tho shape given to them. There may be mentioned here the more or less successful efforts of Bessoii (1791), Johnson (1797), INDIA RUBBER, GUTTA PERCH A, BALATA. Champion (1811), and Clark (1815), to prepare water-proof garments by means of rubber solutions. Hut the actual rubber industry dates" only from 1820. About this time Nadier invented a process of cutting rubber into threads, and of manufactur- ing tissues from the latter. Charles M akin tosh, in 1823, used benzine for dissolving rubber, and created thereby the industry of the water-proof gar- ments which are named after him. But, nevertheless, the useful application of india rubber still presented many difficulties. The ma- terial was not easy to work, required special con- trivances, and the still incomplete methods of dis- solving it rendered it difficult to give definite shape to the articles. These difficulties were overcome in 1836, when it was found, as the result of investigations by Thomas Hancock, that india rubber cut into strips, or passed between rolls and subjected to energetic kneading, can, under the influence of moderate heat, be converted into a tough mass: furthermore, that its elasticity is temporarily suspended, and that in this state it can be given any desired shape. By reason of these observations and discoveries, the industry made rapid progress. However, the permanency of the industry would L / i have been doubtful if it had not been for another invention of still greater importance than the pre- ceding. Besides its impermeability and great elas- ticity, natural rubber possesses the property of being extraordinarily adhesive at an ordinary tempera- RAW MATERIAL. O tore, especially so when two pieces of it come in contact with each other. It shows this peculiarity to a still greater extent at a, higher temperature, so that it becomes sticky and pitch-like, and diffuses a very disagreeable odor, but loses it entirely in the cold, it becoming brittle, and breaking when ex- tended. The German chemist Luedersdorf first noticed, in 1832, that sulphur deprives rubber dissolved in oil of turpentine of its stickiness. Hay ward at the same time used flowers of sulphur for scattering upon rubber leaves, weakening thereby the adhesive power. Neither one of them, however, investigated the subject any further, and it remained for Charles Goodyear, in 1839, finally to settle the question of an india rubber useful in every respect, and to prepare a material which would not break at .a lower temperature nor stick together at a higher. The discovery of Goodyear consisted in that he first subjected the rubber to the action of sulphur, and then exposed it to quite a high temperature. This process is called vulcanization, and. rubber thus treated, vulcanized rubber. Vulcanized rubber ( re- tains its elasticity at a high temperature (up to, 248 F.) as well as at a low one (to 22 F.), and besides offers greater resistance to chemical in- fluences. The discovery of vulcanization gave great impetus to the rubber industry, and rendered possible its almost unlimited development, and in the succeed- ing twenty years .nearly every day brought new O INDIA RUBBER, GUTTA PERCH A, BALATA. discoveries and improvements. Goodyear patented his process of vulcanizing by mechanical means, and, as early as 1842, brought rubber shoes into market which retained their elasticity in the cold, and hence were vulcanized. Shortly after Good- year's discovery, Hancock succeeded after many experiments in preparing a product similar in all respects to Goody ear's. He immersed the rubber in melted sulphur, allowing it to remain until entirely permeated, and then exposed it to a tem- perature of 302 F. He patented this process in England in 1843. Parkes, in 1843, first employed carbon disulphide for dissolving rubber, and later on patented the method of " cold vulcanization," or vulcanizing by means of chloride of sulphur. lie also invented the method of desulphurizing vulcan- ized rubber waste. In 1858, Augustin G. Day took out a patent for an improved method of vul- canizing, and Girard proposed alkaline sulphur for vulcanizing thin articles. The last great invention was that of hard rubber by Goodyear, who succeeded in obtaining a horn-like mass resembling whale- bone or ivory. Finally a patent may be mentioned which was granted to Hancock, in 1846, for the manufacture of rubber articles in moulds, an invention which, next to that of vulcanizing, has become the initia- tory step towards the entire present manufacture of rubber articles, and has created an immense in- dustry. RAW MATERIAL. t Occurrence of India Rubber. As previously mentioned, some botanists claim that rubber is a constituent part of every vegetable milky juice. Many plants carrying milky juice are indigenous to temperate climates, but they contain either no rubber at all, or the quantity is so small that it would not be worth while to make an at- tempt to gain it on a large scale. It is claimed that the milky juice of milkweed (Asclepias) con- tains four per cent, of rubber, and some years ago a company was formed in Canada for the purpose of obtaining rubber from this source, but we have been unable to learn anything further in regard to this enterprise, and believe that the scheme has collapsed. The habitat of the actual rubber-yielding plants is limited to tropical and semi-tropical regions be- tween about the 30th degree of northern and the 30th degree of southern latitude. In these regions there extends around the globe, parallel with the equator, a belt nearly 500 miles in width, which possesses all the requisites for the propagation of rubber plants. The climate is warm and moist, the temperature varying between 79 and 107 F., and the average annual rain-fall being about 7 feet. The milky juice, or latex of the rubber plants of these regions is of about the density of cream, pos- sesses a slight odor of amber, is miscible with w r ater, but not with naphtha, nor with any other substance which dissolves rubber. Its specific gravity is from 1.02 to 1.11, while that of rubber is 0.930. There 8 INDIA RUBBER, GUTTA PERCHA, BALATA. is considerable variation in its content of pure rub- ber, the best quality of latex, that of Para, Brazil, having the following composition : Pure rubber . . .32 per cent. Albumen and mineral con- stituents . . 12 " Water . . . . 50 The rubber plants may be arranged in four fam- ilies as follows : 1. EUPHORBIACE^E : Hevea, Micranda, Manioc or Manihot, Euphorbia. a. Hevea is a variety of Euphorbiacese and belongs to the Jatrophess: The tree is very large and con- tains much milky juice. It is readily propagated, the capsules containing the seeds bursting with a report like that of a rocket, and the seeds are scat- tered a distance of 50 to 60 feet. Up to very recent times Hevea Giiyanensis (called by Linne Jatropa elastica, and by Schreber, Siphonia elastica) has been incorrectly designated as the actual rubber tree called by the Indians of Brazil Seringa or Cahuchu. ' To be sure Hevea Guyanensis is the tree described by La Condamine and Fros- neau, but it yields veiy little latex, which besides contains not much, and even not very good, rubber. The species of Hevea which yields the largest quan- tity and the best quality of rubber is Hevea Brasil- iensis or Siphonia Brasilicnsis. b. Micranda (Benth.) is a tree-like cujtliorbiacea belonging to the Jatrophese. It is indigenous to Brazil where three or four varieties are known to occur. RAW MATERIAL. 9 c. Manioc or maniliot (Plum-Adams), a variety of Jatrophese. Seventy-five species (herbs and shrubs) of it are indigenous to South America. The root is very rich in starch, and is an important article of food in the tropics. From Manihot utilissima and J/. Hipii cassava and tapioca are prepared. Manihot Glazoivii or leitera yields the rubber known in commerce as Ceara scraps y called by the natives manisoba. It grows in dry, rocky soil on mountains, while Hevea flourishes in moist low lands and requires a clayey soil. d. Euphorbia. This is a genus of many species, mostly shrubby, herbaceous succulents, affording an acrid milky juice which draws blisters. Thus far they have been but little utilized, but it may be supposed that in the future, more energetic attempts will be made to obtain rubber from them. 2. ULMACE.E, a genus of Artocarpefe : Different varieties of Castilloa, Ficus, Artocarpus and Cecropia. a. Castilloa, a variety of Ulmacese of the family ArtocdTpese, is indigenous to Mexico, U. S. of Co lumbia, entire Central America, the Antilles and Martinique. b. Ficus belongs to the family of Ulmacese, divi- sion Artocarpess. The genus Ficus is very numer- ous, there being known more than 600 varieties which are indigenous to the tropical and warm moderate zones. Its widest distribution is in the Indian Archipelago and the islands of the Pacific Ocean. While Castilloa is the "rubber tree of Mexico and Central America, the Ficus is the rub- 10 INDIA RUBBER, GUTTA PERCHA, BALATA. her tree of East Asia and Australia. In Africa and America it is but seldom found. Of the Ficus varieties, Ficus elasti&t is frequently seen here in hot houses, and is employed as an ornamental house-plant. It has large, leathery, oval and entire leaves, which are dark green and glossy above. It is readily propagated. A few shoots are allowed to grow until they have four or five leaves, and are then used in spring as cuttings. They are placed in a bottle full of water, and small white roots soon develop from the cut surfaces. The best soil for Ficus elastica is a mixture of leaf and wood mould. c. Artocarpus is a tree belonging to the family Ulmacete. About twenty varieties of it are known to occur in Asia and Australia. The nearly ripe pistillate inflorescence, known as breadfruit, forms a globular sorosis about inches in diameter, and consists of a mealy and spongy receptacle in which the oblong angular akenes are imbedded. The latex of Artocarpus is viscous, and is used by the natives in the preparation of bird-lime. The fruit forms an important article of food. d. Cecropia (Locfl.) a variety of Ulnmcai belong- ing to the CkmoGephalese. Indigenous to Central and South America, 3. APOCYXACE.K : V&rietieaofLandolpkia, l T ireola, Dijera, Hancortiia, Camemria, Paramrrni, l,<'ncnnntis, Artodendron, Alstonia and Ghonemorphia. a. Vahea a genus of AjtocymH-ni , which embraces about twenty species of lianas (climbing shrubs) RAW MATERIAL. 11 indigenous to Central Africa and Madagascar. The fruit is a large berry with eight-cornered seeds with hard perisperm. b. Landolpliia (Pal. Beauc.}. This climbing- shrub is generally considered a species of Valiea, but according to M. Radelkoffer, it is a separate species. c. Urceola. This family comprises about six species of climbing shrubs indigenous to the Ma- layan Archipelago. d. Hancornia. The various species of Hancornia are small trees containing milky juice. They are indigenous to South America, and yield a good quality of rubber. The fruits of Hancornia speciosa (Gom.) and of H. Pubescens (Nees. and Mart.) are known as mangaba, and are highly esteemed by the natives. e. CanK.raria (Mailer) a variety of Apocynacese, order Plumericese, indigenous to the Antilles, are shrubs of which C. lucida and C. latifolia (Jack) yield rubber. /. Paraineria (Benth.), a variety of Apocynacese- Nericese and allied to the Eidysantlierex. To this genus belong two or three climbing shrubs indig- enous to Asia and tropical Oceanica, Paraineria Pierrei, indigenous to Cambodia, yields excellent rubber. g. Leuconotis (Jack) a variety of Apocynaceae- Carisseae. To this genus belong two shrubs con- taining milky juice, which are indigenous to the Malayan Archipelago. 12 INDIA RUBBER, GUTTA PERCHA, BALATA. li. Alstonia (('.), a beautiful tree indigenous to tropical Asia and Australia. The latex is very bitter. i. Chonemorphia (G.), a plant of the variety Apo- cynacese, sub-division Euechitidesc. It is a vine-like climbing plant, three or four species of which are known to occur in the East Indies and in the Malayan Archipelago. 4. AscLEPiADEyK : Callotropis, ('i/mniclniin, and Periploca. a. .Cy,ianchuin (Z/.), a climbing plant of the family Asdepiadese, genus Oynanchese, indigenous to Africa. 6. Periploca Grwca (L.\ a slender climbing shrub which contains milky juice, is indigenous to Africa. c. Callotropis procera (P. Br.), a shrub 6 to 10 feet high, indigenous to Northern India and westward through Asia and tropical Africa. It carries beau- tiful large flowers of a rose and purple-red color. It will be readily understood that the quantity of milky juice in the varieties of plants above enu- merated not only varies, but is also dependent on the age of the plant, the nature of the soil, the season of the year, and even on the time of the year when it is obtained. It is also evident that the quality of the milky juice, and consequently of the rubber, depends on the manner in which the latex is ob- tained and the globules of rubber are separated. While Hevea brasliensis must attain- an age of at least 15 to 20 years before it can be tapped for milky juice, and reaches the height of productive- ness when 25 years old, which to be sure it retains HAW MATERIAL. 13 to an age of 100 years, Manioc yields milky juice in 10 years, and Urceola even in 5 years. Climate exerts an important influence upon the quality as well as upon the quantity of the milky juice. Gen- erally speaking, it may be said that the yield is remunerative only in the tropical zone, that is where the temperature varies between 68 and 104 F. In the temperate zone, between the 30 northern and 30 southern latitude, great variations occur, so that, for instance, a plant which flourishes exuber- antly in Brazil, cannot be acclimatized in India. According to climatic conditions, the principal rubber plants may be arranged in the following geographical groups : South America (plains) : Hevea, MicrcnuJa. South America (mountains) : Manioc, Hancornia. Central America : Cast-Ulna. West Africa : Landolphia, Vahea, Callotropis. East and Central Africa : Vahea, Landolphia. India : Fini*. WUlughbeia, Cynanchum, Cameraria, Australia : Ficus, Urceola. It has been generally supposed that all rubber plants require a moist soil exposed to the tropical sun. Such, however, is only the case with Hevea braxiliejtsis. Hancornia flourishes in the sandy tracts of Pernambuco, Maranham and Bahia, and Manioc upon the steep granite rock of Ceara or Clara. The last-named plants withstand even extraordinary drought. While everything else is destroyed by the hot wind, these plants flourish and yield an abund- ance of milky juice. 14 INDIA RUBBER, GUTTA PERCHA, BALATA. To be sure rubber plants grow most luxuriously where the soil is exposed to inundations or regular periods of rain. In a very wet season the milky juice is watery, and contains but little rubber, while in dry seasons the content of rubber is greater, but the quantity of milky juice less, and the work of obtaining the juice is more difficult. The content of rubber in the latex varies between 15 and 40 per cent. With a content of less than 15 per cent., the work of gathering the latex is not remunerative. Cultivation. \ It is obvious that in view 7 of the growing import- ance of the rubber industry, attempts should have been made to acclimatize the rubber plants in other than their native countries. England took the initiatory steps in this direction, and experiments were made to acclimatize in her Asiatic colonies such varieties of plants as might prove suitable to the soil and climate, India being selected as the most promising field. The first experiments with an enclosed plantation were made in 1860 with the native jffy'c?/s, which produces a remunerative yield only after a growth of '25 years, and can be tapped only every three years. When fifty years old the Ficus tree yields every three years about 45 pounds of rubber. This calculation, and especially the long time re- quired before (he tree becomes remunerative, did not hold out sufficient inducements; and besides, tests made in the meanwhile showed that the rubber ob- RAW MATERIAL. 15 tained was of inferior quality to that of Para and ( Vara. Hence the further cultivation of this variety was discontinued. Consideration was also given to the introduction of Urceola elastica, which yields the first crop in its third year, and to Urceolaesculenta, which from its seventh year on yields one to four pounds of rubber, but it was claimed that Castilloa elastica would prove most remunerative, though its rubber is not of the first quality. In 1875, the administration of the Kew Botanical Garden authorized Robert Cross, a distinguished botanist and gardener, to make a journey to Central America for the purpose of study- ing the different varieties of Castilloa, with a view of introducing them in the English colonies. How- ever, the plant, which flourished in the Kew hot- houses in the hands of skilled gardeners, died in the open air, the moist climate of its native country where it rains nine months in the year being want- ing. In 1876, Cross was again commissioned to bring young plants of Hevea brasiliensis from the plains of the Amazon river. Though the natives jealously guard the trees in order to retain a monopoly of such an important industrial plant, Cross succeeded in shipping a number of Hevea to Kew. The result, however, was the same as with Castilloa. The tree to be sure grew in various kinds of soil, but reached luxuriant development only on the banks of run- ning streams where a moist soil had not degenerated into a swamp. On the Amazon river ten days 16 INDIA RUBBER, GUTTA PERCHA, BALATA. seldom pass by without rain, and every morning the trees are enveloped in a heavy dew. The southern portion of Burma alone offers a climate approximately like it. Beside the difficulties growing out of climatic differences, another important point had been left out of consideration in making these experiments. A country for the introduction of a rational cultiva- tion of rubber trees to be carried on in an orderly manner, must be habitable, so that people can live there and stand continual, regular work. The territory of Assam which was selected for the ex- periments is just as little suited for habitation as the native country of Castillio and Hevea, the regions of the Amazon and of the San Juan, which only the Seringueiros, as the rubber gatherers are called, can penetrate during the so-called dry season, and where, exposed to fever and tormented by insects, they work and impatiently await the end of the harvest. These are the principal reasons which rendered a rational culture of these two trees im- possible not only in India but also in America. Acclimatizing experiments with Manihot glaziovii which yields the Ceara rubber were more successful. It requires a stony soil, and though it demands moist- ure, can stand great drought. Its habitat is the most mountainous and the roughest regions of Brazil, where a temperature of 77 to 86 F. prevails. It flourishes at a height of 6,000 feet above the *ea, re- quires no special care, and readily adapts itself to the climatic conditions of its adopted country. RAW MATERIAL. 17 The seed coat is of remarkable thickness, and very hard, and the natural process of germination occu- pies, it is said, more than a year. All that is neces- sary to hasten this, is to assist the seed coat in split- ting, which is best effected by holding the seed firmly and rasping off with a file both edges at the radicular end, recognized externally by possessing at its side a flat two-lobed appendage, technically known as the caruncle. It is best not to file off the actual end, as the radicle of the embryo may then be injured. After this treatment properly per- formed, the young plant appears above ground in two or three weeks. The seedlings require no par- ticular attention. They grow rapidly and may be finally planted out at distances of 20 feet. Planta- tions may also be formed by cuttings, which take root as easily as a willow. They should be from the points of strong shoots, and about one foot in length. In planting, each shoot may be put down in the soil to a depth of six inches. On loose, sandy soil, or exhausted coffee land, plantations may be formed at little expense. Hard, diy gravelly wastes, if found to support any kind of bush, are also suit- able sites. In strong land, holes may be made with an iron jumper, and a stout cutting put into each, and filled with pebbles. On bare or thinly covered portions of rock, the cuttings might be laid down flat, and a little heap of stones, or any kind of debris, about the size of a mole-hill, piled over each, care being taken that the extreme point of each cutting with a bud is left uncovered. 2 18 INDIA RUBBER, GUTTA PERCHA, BALATA. The habits of Manihot pointed it out as being well adapted for cultivation in Ceylon, and atten- tion was concentrated on it as being the quickest growing, and promising not only early, but hand- some returns. Several plantations- were started in the Dumbara valley, and the returns of rubber were said to be profitable until it was found that the trees and their shade were inimical to the more important cacao trees underneath. According to the latest reports, the culture of Manihot glaziovii has been abandoned in the Java Botanical Gardens because " the promised magnificent results have in no respect been fulfilled." According to a circular issued from the Royal Botanic Gardens, Peradeniya, by the Director, Mr. J. C. Willis, January 27, 1898, the only important rubber at the moment in Ceylon is the Para kind. The tree is well suited to the climate of the low country in the southwest of Ceylon, is readily culti- vated, and gives a fair yield of rubber. Hevea brasiliensis, the botanical name of the Para rubber tree, forms a moderately tall tree, not much branched. The seed is very large, weighing about half an ounce. It has a hard seed coat, and the interior substance is very oily. The seed soon loses its power of germination, and ought to be .sown within a week of its falling from the tree. Germina- tion takes place very rapidly, and a long tap root is soon produced. The seed should be sown about an inch deep in well prepared soil, in nurseries, or, if preferred, in bamboo pots or baskets. They should RAW MATERIAL. 19 be kept shaded and watered, and when the young plants are from 18 to 24 inches high, they may be planted out. Good results are also obtained by stumping, the plants being allowed to. grow about three feet high, then taken up, and the main root cut across about a foot below the ground, but the method of planting out the smaller seedlings is per- haps preferable. The plant may also be propagated by cuttings. The method employed in the Botanical Gardens has usually been to take cuttings near the ends of the branches, but further back than any of the leaves. Each cutting is about a foot long, and as thick as a lead pencil, and is cut off at both ends by oblique cuts made just below leaf scars. This method is some- what precarious ; sometimes nearly all the cuttings grow, at other times only a small proportion. The seedlings, stumps or cuttings should be planted out during rainy weather in prepared places. Holes should be dug and filled with good soil, a little manure being often of advantage. The young plants require to be lightly shaded for a time until they are established, and probably for the first two or three years they will grow the better for a certain amount of shade, such as would be given by narrow belts of trees running through the planta- tion. These belts should be arranged to act as wind belts, as the Hevea is easily injured by wind. By the time the trees are about three years old, they will have grown up to a height of about 25 or 30 feet, and form their own shade. Various distances 20 INDIA RUBBER, GUTTA PERCHA, BALATA. apart have been tried in planting Hevea, but the best results have been obtained by planting eight or ten feet apart each way. Hevea is a surface-feeding tree, and catch crops should not therefore be grown between the trees, which require all the nourish- ment that the soil can afford. Weeding is also re- quired the first year or two, but afterwards the trees form a dense shade under which but 'few weeds grow. The yield of rubber from very young or slender trees is too small to make their tapping worth while, and it is best for many reasons to abstain from tapping a tree until it has reached a girth of two feet. In a large plantation the girth of the trees always varies between wide limits. A few trees may be fit to tap after the sixth year, and in every subsequent year more and more trees will reach the size necessary. In favorable localities the bulk of the trees should be in bearing before the end of the eleventh year. Experiments in the rational cultivation of rubber trees were also made in other countries, especially in the French colonies, for instance, on the Congo. In consequence of the irrational manner in which the natives treated the indigenous rubber plant, Landolphia, it w r as feared that in time it would entirely die out. E. Pierre, the creator of the botan- ical garden at Libreville, endeavored to prevent this danger by the acclimatization of foreign plants, and he also selected the Manihot as had been done in Ceylon. It would seem that the experiment has RAW MATERIAL. 21 been successful, Pierre reporting in regard to it as follows: "A single tree which I planted in 1887 has furnished up to the present time (1898) 115 trees. The .plant, which M. de Brazza has endeav- ored to introduce as much as possible among the natives, has a great future for this country. The tree .introduced in 1887 has already yielded 14,000 to 15,000 young plants, of which several thousand have been delivered to the natives in the remotest parts of the Congo territory." The director of the garden at Libreville hopes to be able to distribute in a short time more than 200,000 young shoots for stocking new plantations. On the other hand, a young French colonist, who has for some years resided in the interior, in X'Djole on the Ogooue writes as follows : " It is true that the Pahouins have been furnished with young manihot plants, and explicit instructions regarding their cultivation have been given. But in most cases the natives have thrown away the shoots, and when not watched, continue in their barbaric destruction of the rubber trees. Why, if by penetrating a short distance into the interior the}- are assured of an easy and rich crop, should they undertake the laborious task of stocking a plantation, and wait for years for a crop which they may not live to gather and enjoy the benefits of? Hence it is not sufficient to lay out plantations and hand over the young trees to the natives. The care of these plants must be entrusted to the colonists in order to obtain favorable results." 22 INDIA RUBBER, GUTfA PERCHA, BALATA. According to Paroisse the Manihot cultivated in Libreville is not the one planted in Ceara and Cey- lon, but a variety indigenous to an island on the south coast. Acclimatizing experiments have also been made in Coch in-China, where the soil and climate are especially suitable for the cultivation of rubber plants. Hevea gnyanensis has been successfully raised in the garden at Saigon. But whether this enterprise will be crowned with better success than in the Kew garden remains to be seen. Experi- ments have also been made in Reunion. Attempts towards a rational cultivation of rubber plants are now made in Peru, Columbia, Costa Rica, Mexico, and even in the Amazon River dis- trict, and nearly everywhere the success attained corresponds to the efforts made. In Mexico a number of enterprising citizens are deeply interested in the project of starting rubber plantations, and as the soil and climate of portions of that country are suitable for that purpose, there is no doubt but that their efforts will be crowned with success. Castilloa elastica is indigenous to the Isthmus of Tehuantepec, and particularly to that region lying near the Trinidad and Colorado rivers in the south- eastern portions of the states of Vera Cruz and Oaxaca. In these districts it is found growing under varying conditions, though with certain limi- tations, for example: from sea level to an elevation of 1500 feet. In some localities there are, doubt- UNIVERSITY) RAW MATERLkPA , 23 less, exceptions where the tree may ascend the mountains 1000 feet higher. Careful observation justifies the belief that the zone wherein the tree attains its best development lies between sea level and 1500 feet altitude, and within a virgin forest district, with a mean annual temperature approxi- mating 80 F. or a range of from 60 minimum to 9f> maximum ; also a well distributed rain fall ap- proximating 100 inches per annum. The trees are found growing in various soils, seldom in arid, gravelly districts, and when so found presenting a stunted appearance. They do not occur in swampy or'inundated districts. They seem to prefer reddish clay soil where drainage is good, or black or reddish sandy loam. Occasion- ally they grow in rocky soil with deep deposits of of leaf mould, but only where there is much humid- ity and shade. They reach their finest develop- ment, however, in alluvial soils mixed or overlaid with dark forest loam, and in company with a fine growth of other trees, and more especially when the land is somewhat rolling in character, insuring proper drainage. In such land the w r ild trees exist in greater number near the sides of arroyos or streams, which rarely overflow their banks, though the trees near and on the summits of these rolling hills are quite as fine in development. Probably the greater number in the former case is owing to the fact that the seeds falling from trees above, are washed down and find lodgment in the more level places. Experiments in planting have demon- 24 INDIA RUBBER, GUTTA PERCH A, BALATA. strated equally as good growth away from the margins of streams as upon them. The seed matures the early part of June, just about the beginning of the rainy season, and soon falls from the trees. Germination takes place very quickly in about ten days or two weeks. The vitality of the seeds is very short, and rnuch disap- pointment will be met with by those planting seeds a few months old. The seeds should be gathered daily, when they commence to ripen, placed in a barrel with a gallon of water to about a peck of seeds. In eighteen hours fermentation will have sufficiently loosened the pulp, without injury to the germ, so that it can be washed off. The seeds should then be laid upon mats in a dry, but not too sunny position, for not longer than a week. They are then ready for planting. Under this plan 90 per cent, of seedlings may be procured. If gathered and allowed to remain in a mass for a week or more with the pulp on them, they genera f e a fierce heat, which utterly destroys the germ ; while if washed and dried, as above stated, but not planted for two or three months, the yield of seedlings will be insignificant, if not a complete failure. The cotyledons undergo a rapid chemical change, leav- ing no nourishment for the germ. It is thus easy to see how a whole season may be lost in starting an enterprise of this kind. Seeds planted in June may be transplated the end of August, and attain a height of three feet by the following June. From experiments made on. the RAW MATERIAL. 25 Isthmus of Teh u an tepee, it appears that the forest system of planting is more rational than the com- plete clearing of the land and planting in regular orchard form, as it entails less labor and expense, and affords the natural conditions of partial shade and a greater degree of humidity. These conditions do appear to be essential to the highest development of the tree and the greatest yield of sap. Hence this system involves simply the clearing of the under-growth and planting the seedlings at as nearly uniform distances as the standing forest will permit, only destroying such forest trees as are unnecessary to the fulfillment of the demands of shade and humidity, thus increasing the number of rubber trees per acre. If, however, a regular plantation in regular orchard form is to be started, and the land set aside for the purpose is covered with trees, these must be felled, and the under-growth cleared only where the young trees are to be planted, providing no side planting is to be made. This work must be per- formed in the months of March and April, and im- mediately after Indian corn should be sown in the open spaces 15 inches apart. This operation is simply done by making a hole in the ground, dropping in a few grains, and covering over with the foot. Should the planter wish to adopt the most economic system, and thereby obtain the greatest return for the money invested, it would be advisable for him to plant besides corn, cotton, bananas and coffee. But the attempt to plant Mocha coffee must not be 26 INDIA RUBBER, GUTTA PERCHA, BALATA. made in. elevations less than 1000 feet above sea level, neither on plains, nor where the temperature exceeds 85 F. In the latter case the acreage to be planted must be stubbed, and the under-brush forked in or burnt before sowing the corn ; then line and stake the plot in rows 15 feet apart. Peons who are posted in this kind of work, especially in coffee planting, have a long cord or rope 24 to 36 varas * in length on which they mark the divisions with inks made from dye-woods in the forests in these sections. The cord is held by two men, and another one marks the holes with his garrocha, leaving a stake in the excavated place every 15 feet in the row. The rule of setting the trees at such distance would ensure larger size, and a greater flow of sap. As to shade, if the young plants have been taken from woods under shelter, then natural trees must be left on the plot before clearing to protect them from the strong rays of the sun until they are 10 or 12 feet high, and have a prosperous appearance. This must not be overlooked, as the plant will suffer a great deal from transplanting even when that operation is done under the best of circum- stances. But if the young plants are obtained from unsheltered places, or from a nursery established in an open space, they having grown stronger and stouter will require no shelter, and will flourish more rapidly and vigorously than if they had shade. * 1 vara = 32.9 inches. RAW MATERIAL. 27 If the seedlings or cuttings can be obtained within a few miles from a plot, it is advisable even to pay as much as $2.50 per 100 than to wait 12 months for the seed to grow in the nursery. When the place where the supply of young plants or cuttings is to be had is too distant, the expense of transpor- tation would be enormous, and they would suffer to such an extent as to render them unfit and risky for transplanting. The only practical method in that case is to start a nursery. For this purpose a rich sandy loam should be selected. Beds are made 6 feet wide by 15 to 20 feet in length, leaving a walk 2 or 3 feet wide. The seeds are sown 8 inches apart in rows 10 inches distant one from another. This operation is done in the beginning of June or a few days after the rains have started, and by merely marking the ground, about an inch deep, with a stick, dropping the seed in, and covering it with vegetable mould. In 12 months the seedlings are about 24 inches high and ready for transplanting. All weeds and grass must be carefully removed with the hand from the bed as they appear, and the earth watered when it seems dry, which is best done in the after- noon. In the latter part of May or in the first days of June, when the rainy season commences, the seed- lings, young plants or cuttings, are transplanted in the cleared plot between the corn and cotton, 15 feet each way. In removing the seedling or young plant, as much of the original soil as possible should 28 INDIA RUBBER, GUTTA PERCH A, BALATA. be left attached to it. The earth must be opened sufficiently to place the plant at the same depth as in the seed bed, and then press down the earth with a spade so as not to allow an} 7 hollows around the tree. The plot planted with rubber trees should be inspected now and then in order to judge how they are progressing, and to replace the plants that have withered and died. In July or August it will be necessary to clean the corn, weed the plot, and after harvesting the corn, banana suckers (hijos) can be planted 7 feet apart between the rows of rubber trees. In Chiapas and Tabasco, cacao trees are set a few feet from the 2 or 3-year-old rubber trees, the latter acting as shade for the former in lieu of the regular rnadre protector or shade tree. Vanilla trees can be attached to the cacao tree, and by that means, after the lapse of 6 or 7 years, the planter has three or four different crops to harvest. Furthermore, bees could be raised on the place which would act ^s a medium to fertilize the vanilla flowers, and give a hand- some profit from honey and beeswax. Again, should the proprietor not want ajiy side planting, cattle, which bring a good income in those sections, may be permitted to graze on the land as soon as the young trees are well rooted and have grown over 20 feet in height. After going through the work of transplanting, the only care in the cultiva- tion of the tree, thereafter, is that of keeping the ground free from all weeds and the rank vegetation of the tropics. I;A\V MATERIAL. 29 It is difficult to give the cost of establishing a rubber plantation, but it has been estimated that the entire expense for a plantation of 100,000 trees will not exceed 25,000 dollars Mexican currency. Manner of obtaining Crude Rubber. The quality of the crude rubber depends largely on the method employed in obtaining the latex, and the manner in which the rubber is separated from it. There are two methods of obtaining the milky juice, namely : 1. By cutting down the trees. 2. By tapping the trees by making incisions in the bark. The first method cutting down the trees is still employed in Africa and Asia, and especially in the Indian Archipelago, where, within a few years, the Borneo rubber was only obtained in this manner. Generally speaking, this method must be condemned as irrational and destructive, though it might be permissible if the plants die anyhow in conse- quence of tapping, and in the case of trees which have to be removed in thinning out primitive forests. It is asserted by the natives of Peru that Il'iiicornia speciosa dies in consequence of insects attacking the places where the incisions have been made. On the other hand, by cutting down the tree just above the ground, the stump soon sprouts again and throws out new shoots, so that in a few years there will be a group of trees where formerly was but a single tree. 30 INDIA RUBBER, GUTTA PERCHA, BALATA. Cutting down the trees for the purpose of thinning primitive forests is permissible if carried out in mod- eration and with judgment, it being useful, for in- stance, in the dense forests of Africa, since by the admission of air and light a more vigorous growth is promoted. However, tapping by making incisions is the most rational manner of obtaining the sap, but care must be exercised to prevent injur} 7 to the trees. The method of tapping at present employed on the lower Amazon river is decidedly the best and most practical. The operation is as follows : The Seringueiro, or as he is frequently called, the Cauchero, begins to work immediately at day- break, or as soon as he can see to move among the trees. His tools consist of a machado a small axe with a short handle and an edge a little over an inch wide further a bucket and a number of small tin cups slightly concave on one side in order to fit the convexity of the tree trunk. The trunk of the tree having been carefully cleansed, and the ground around the tree swept, the collector takes the axe in his right hand and, striking in an upward direction as high as he can reach, makes a deep upward sloping cut across the trunk, which always goes through the bark and penetrates an inch or more into the wood. The cut is an inch in breadth. In this manner each tree is tapped in twelve places. Some of the col- lectors arrange the incisions in the form of a V, and others in spirals, while others again simply RAW MATERIAL. 31 make them vertically, one above the other, from a point up to which they can reach with the hand down to a few -inches above the ground. The incisions having been made, the tin cups are fastened to the tree with a piece of kneaded clay, of which the Seringueiro carries a supply in his bag. One man is apportioned to a path or district containing 100 trees. When he has tapped and cupped his trees, he sits dowai at the end of the path for half an hour or so. As soon as he perceives that the tree last tapped has ceased to drip the milk, he starts at a trot on the back track, detach- ing and emptying the cups into his calabash as quickly as possible. The cups he leaves upside down at the base of the tree. Speed throughout is a great object, as the milk speedily coagulates. The quantity of milky juice obtained varies according to whether the tree is vigorous or decaying, but at an average each incision yields in one to three hours about 0.21 1 gill. The yield is, however, not the same every year, it being influenced by long continued rain and extraordinary drought, [is well as by the incisions having been made either upon the sunny or shady side of the trunk. The latter circum- stance explains the fact why some natives prefer tapping at nightfall. Besides, the natives assert that the milky juice is more abundant during full moon than at any other time. The quantity of sap obtained from each tapping of 150 trees amounts to about 52 quarts of milky juice, or about 80 pounds of crude rubber. By 32 INDIA RUBBER, GUTTA PERCH A, BALATA. counting upon 20 tappings each year, the yield would represent a product of about 1600 pounds of crude rubber. On the Upper Amazon tapping is effected in a similar manner, but the work is done less carefully, and the tools used are* of a more primitive char- acter. The further the collector penetrates into the virgin forest, the less baggage he wants to carry. A shell answers for a cup, and for the small machado the old-fashioned broad hatchet is substituted which has proved so destructive to the rubber trees. With slight deviations, the method of tapping is the same throughout South America, The arrange- ment, number and depth of the incisions may vary, as well as the mode of harvesting, but the principle is the same. In Central America, where Castilloa elastica is the principal rubber tree, a different treatment is re- quired. The incision is replaced by a puncture, and is made with a smaller and finer tool than the machado. In Africa, the operation of tapping is still carried on in an imperfect and irrational manner, almost every region having its own method. As a rule, the incisions are cut too deep, and in consequence of this the latex is mixed with other juices, which impairs the quality of the rubber, and the African product, which is naturally inferior to the South American, and especially to the Amazon rubber, becomes thereby of still less value. In Asia, especially in the regions where the rub- RAW MATERIAL. 33 ber is obtained from the different varieties of Ficus, incisions of an elliptic shape extending to the inner bark or bast are made in the lower portion of the trunk and in the aerial roots. The yield of latex depends on the season of the year. While the quantity obtained in February and March is small, the content of rubber is considerable, and for this reason tapping during these months is most remun- erative. The conditions are similar in August, when the content of rubber in the latex is 30 per cent., while in other months it decreases to 10 per cent. In Australia the methods in use are generally the same for trees of a similar nature as in Asia, but the destructive method of felling the trees is also in vogue, especially where through the carelessness and shortsightedness of the authorities the matter is left to the natives themselves. Urceola elastica is especially subject to such thoughtless destruction. The stem of this climbing plant is cut up and the pieces are laid over large vessels for the sap to exude, and when the flow becomes slow, it is assisted by a brushwood fire. Coagulation of the Latex. The latex obtained by cutting down or by tap- ping the plants separates the rubber contained in it only when subjected to a particular method of coag- ulation which varies in every country, nay, in every province, and even from one side of a river to the other. Hence it frequently happens that there is a great variation in the quality of rubber 3 34 INDIA RUBBER, GUTTA PERCHA, BALATA. obtained from the same plant and in the same country, according to the coagulating process in use. Dr. F. von Hoehnel and James Collins have de- scribed the various methods of coagulation actually in use, and the following summary showing the various methods, and the countries in which they are employed, is based upon their researches : The coagulation of the latex is effected : I. By heat. 1. By artificial heat : a. Dry heat or fumigation on the Amazon, in New Caledonia. b. Moist heat, in Mexico, Central America. 2. By natural heat : a. Separation of the serum by means of the soil, in Angola (Lower Guiana). b. Separation of the serum by means of the human bod} 7 , in Congo ; Angola. c. Evaporation upon even surfaces, in Ceara ; Angola. II. By skimming : 3. By skimming after increasing the fluid to double its quantity by the addition of water, in Bahia. 4. Skimming after a period of rest, addition of four to five parts of water, draining, washing and pressing, in Bahia ; Congo. III. By disintegration : 5. Chemical disintegration by means of reagents, Matto Grosso (interior of Brazil) ; Pernambuco ; Maranham. RAW MATERIAL. 35 6. Chemical disintegration by the use of plants as reagents, in Peru ; Guatemala ; Nicaragua ; Gambia ; Madagascar ; Casamanza. IV. By natural or artificial heat in combination with chemical disintegration, in Gambia ; Sene- gal ; Madagascar ; Casamanza. A brief description of the various processes of coagulation may be of interest. Coagulation by artificial dry heat or fumigation. This method is especially suitable for the latex of Hevea and Micranda, and is chiefly employed on the Amazon in the preparation of Para rubber, which on account of its purit} 7 , durability and elasticity is highly prized and considered the best quality. This method, which is decidedly the best, however, is also employed in other parts of Brazil, as well as in Venezuela and Guiana, and is as follows : The Seringueiro or rubber gatherer carefully re- moves from the tapped tree one cup after the other and empties the latex into a bucket or large bottle- gourd, which is covered with a wide-meshed net and provided with a rope handle. The empty cup is then again secured under the incision, which, how- ever, is first carefully examined and opened if, as is frequently the case, it has been closed by the coagu- lation of latex. The thin skin of coagulated latex is removed from the incision and carefully laid aside. The sap from two or three trees will fill the bucket. If the hut of the Seringueiro is in the immediate neighborhood of the trees, the entire yield of latex is emptied without special care into a 36 INDIA RUBBER, GUTTA PERCHA, BALATA. large tub ; but if the Seringueiro has to traverse a considerable distance before reaching his domicile, 3 per cent, of liquid ammonia is added to the latex to prevent coagulation on the road. The actual preparation of rubber, that is, fumigation, com- mences only when all the latex has been collected. For this purpose a fire of brush-wood is kindled, and on this a narrow funnel-shaped pot of clay, called fumeiro, is placed. When the smoke is of sufficient density, which the Seringueiro tests with his hand, palm nuts are thrown upon the fire, the nuts used being the fruits of the Urucury and Uauassu palms (Attalea excelsa and Monicaria saxifera) which, as a rule, can be had in the imme- diate neighborhood of where the work is carried on. However, nuts for the creation of smoke are only used on the Lower Amazon, where the best rubber is prepared, the smoke of brush-wood being con- sidered sufficient in other regions. When the smoke is of sufficient density, the Seringueiro, with the bucket of milky juice by his side, seats himself before the fire, clips a club-shaped piece of wood with a flattened clay mould at the end into the milk and turns the juicy end round and round in the smoke issuing from the pot. In half a minute the milk is changed into a skin of reddish tint. When tins is firm the stick is again dipped into the milk, and so the process goes on, layer being added to layer, until a sufficient thick- ness has been obtained. Another stick is then taken up, and the work goes on until the juice lias RAW MATERIAL. 37 been exhausted. A good workman can in this manner prepare in one hour five or six pounds of rubber. When the cakes are completed they are slit up with a sharp, wetted knife, and after being hung in the open air to dry for a few days, they are ready for sale. The flat rounded Para rubber cakes made in the manner described are known in com- merce as " biscuits," and command a higher price than any other kind of rubber. The most difficult portion of the process of pre- paring rubber according to the method above de- scribed is without doubt the operation of fumigating. In order to understand thoroughly the efficiency of the process, a knowledge of the composition of the fresh latex is necessary. The milky juice of Hevea and Micranda from which Para rubber is prepared contains : Rubber, . . . .32 per cent. Organic substances subject to putrefaction, and min- eral substances, . .12 per cent. Water, . . . . 55-56 " Liquid ammonia (added), up to 3 " Traces of resin. To be sure no other latex possesses such excel- lent qualities, but by taking into consideration the care exercised in collecting the sap, and in the sepa- rating process in order to prevent, on the one hand, loss in removing the watery constituents, and, on the other, to render innoxious the substances pro- ducing putrefaction and fermentation, it will be 38 INDIA RUBBER, GUTTA PERCHA, BALATA. evident that the superior quality of the rubber pro- duced is more due to the excellent treatment than the quality of the milky juice. The latex contains substances subject to putrefac- tion or fermentation whch may be fatal to the rub- ber. To render these substances innocuous, the natives have, instinctively, without any scientific knowledge, found the most simple means. First, by the repeated action of moderate heat the greater portion of the water contained in the serum is re- moved, whereby fermentation takes place almost instantaneously, but at the same time the incomplete combustion of the wood produces carbon, which is a very effective antiseptic, and cannot but exert a beneficial influence. Finally, by the combustion of wood creosote is evolved, which mixes with the smoke, and has also an antiseptic effect upon the nitrogenous substances. It is not positively known whether the smoke of the palm nuts mentioned above contributes to this antiseptic action, but it is alleged that its benefit consists in its absorption of the oxidized resin of the juice, and it is the small- ness of the quantity of this resinous body in Para rubber that gives it the highest value in the markets of the world. In connection with this an experiment may here be mentioned which may be considered an imitation of the process of coagulation in use on the Amazon, and which has been very successfully carried out by Grandjean and Waser in New Caledonia and the Loyalty Islands. In his work on " The Coloniza- RAW MATERIAL. 39 tion of the New Hebrides" (Paris, 1895), Dr. Daville speaks in reference to this process as follows : " The operation of tapping is very simple. Beside the Brazilian tin cup, a conical gutter tapering to a hollow prism, and provided on one end with a sharp blade, and on the other with a hook, is required. The blade effects the incision in the bark and serves at the same time for securing the gutter to the tree. The milk} 7 juice exuding passes through the gutter into the tin cup suspended to the hook. It is easy for the workman to suspend the cups in the morning, to empty them every three or four hours into a larger vessel, a bottle-gourd, or still better a tin can, and to replace them on the tree." The further operations correspond to those on the Amazon river already described, and the result is an excellent and valuable quality of rubber. It remains to mention a few details of the prep- aration of some kinds of Para rubber of less fine quality, namely, Para Grossa, Para entrefina and Sernamby or Nigger-head. From the residues in the cups, or adhering to the lips of the incisions, a second quality of rubber is prepared by throwing them together and shaping into a flat ball. This ball is from time to time dipped in fresh latex, and after each such coating fumigated like fine Para. Finally it receives several coatings of fresh latex, so that externally it has the same appearance as the best quality of Para. However, this deception is readily discovered by cutting into it with a knife. This quality of rubber 40 INDIA RUBBER, GUTTA PERCH A, BALATA. contains a far greater quantity of water and a consid- erable amount of nitrogenous substances subject to putrefaction, the principal reason for this being that the skin of rubber taken from the incisions has been formed from the latex by the influence of natural heat. This process of coagulation will be fully de- scribed later on, and will explain the defects of Para entrefina. Finally all the residues of less value from fine Para and Para entrefina the scrapings from the moulding sticks, the residues in and around the vessels, etc. are kneaded into blocks and packed into boxes or barrels. The whole mass sticks to- gether, and acquires the shape of the receptacles. This rubber, which is, of course, of little value, is known as Sernamby or Nigger-head. It is very moist, frequently contains non-coagulated latex, even vegetable and mineral particles, and has not passed through an antiseptic process. Coagulation of. the latex by means of mo'st artificial heat or by boiling. This extremely primitive method is employed by the Indians of Mexico for the coagu- lation of the latex of Castilloa. The latex obtained by making an incision or puncture in the plant is collected in a piece of bark or in a pot, strained, and poured into a kettle under which a brushwood fire is lighted. As with animal milk, a layer of cream is formed under the influence of heat, which by continued boiling becomes solid, and can be sepa- rated from the watery constituents. In this manner pieces of rubber are obtained which, before they are RAW MATERIAL. 41 brought into commerce, are dried and pressed to deprive them as much as possible of moisture. This process is evidently very defective. The mass is not sufficiently boiled to destroy all sub- stances producing putrefaction and fermentation, the product is not subjected to sufficiently strong pressure to remove moisture, and finally, notwith- standing that the latex is strained, the treatment is not sufficiently careful to remove all vegetable and mineral impurities. In fact, experience has shown the correctness of this assertion, since on examining pieces of rubber prepared by boiling the blackish mass will be found to be full of bubbles filled with a thick, greenish liquid containing sand and splinters of wood. More recently a better quality of rubber also prepared from the latex of Castilloa has been introduced from Mexico. It is of a pale brown color, and of an agreeable odor, and contains neither sand nor other impurities. It is almost as firm as Brazil rubber, and the loss in working it is only 12 to 15 per cent. It has not been possible to ascertain the process by which this variety is pre- pared, but it may be assumed that the latex receives an addition of sea-salt. In British India, the latex is also boiled in preparing the Assam rubber ob- tained from Ficus. Coagulation of the latex by natural heat. The soil as a means of separating water. Coagulation by nat- ural heat is chiefly in use in East Africa. Although it is occasionally employed in other regions, it would, however, appear that all defective appliances, 42 INDIA RUBBER, GUTTA PERCHA, BALATA. which are the chief reasons of the inferior quality of the African product and its low price, are special characteristics of the natives of Africa, whose laziness is perhaps only surpassed by their rapacity. The method employed by some tribes on the Congo and in Angola, who chiefly tap Landolphia, is, according to Jeannest, as follows : The native taps a tree without caring whether it is destroyed thereby or not. The sap trickles down the trunk of the tree and falls upon the ground, the latter not having been even properly cleaned. The hot air immediately commences to absorb the water of the latex, so that the latter is half coagulated be- fore it reaches the ground. The hot, dry ground absorbs the rest of the liquid, and nothing remains for the negro to do but to lift up the rubber. It is not worth while to criticise such a primitive method. However, the natives, instead of removing mineral impurities as much as possible, add them intention- ally. Of course the soil, which in this process serves as a filter, can only absorb the fluid from the outer portions of the mass, since a skin is quickly formed upon the surface, which no longer allows the serum .to pass through. In consequence of this, nitrogen, sugar, resin, etc., remain in the interior, the rubber is soft and sticky, and possesses an abominable odor, which, however, shows itself only later on. The loss in washing these varieties of rubber in the factory is very great. Coagulation by natural heat; evaporation upon the human body. This very original method is also in RAW MATERIAL. 43 use by the natives of East Africa, and is decidedly preferable to the process above described. On the Congo, it is carried out, according to R. V. Merlon, as follows : Before tapping the plant, the negro divests himself of his very limited clothing, then makes an incision, catches the latex in his hands, and covers his entire body with it. Covered with this curious coating, he returns to his domicile. A crust is soon formed, which can be removed in patches, and is rolled into a ball. According to Dr. Welwitsch, some tribes in Angola proceed in a similar manner. The negro presses his hand against the trunk of the tree im- mediately below the incision, and allows the exud- ing milky juice fa run over his arm. When the coating is of sufficient thickness he, commencing at the elbow, draws the rubber off like a glove and rolls it up. Although this method cannot be recommended, as the substances producing putrefaction are not de- stroyed, it has the advantage of no foreign sub- stances being mixed with the latex. Evaporation of moisture is quite complete, as coagulation takes place in very thin, often repeated layers upon a large surface, the heat emanating from the human body also contributing essentially towards that end. Coagulation by natural heat. Evaporation upon other even surfaces than the ground. This method is chiefly in use in Brazil in the preparation of Ceara rubber (Ceara scraps) which is obtained from Mani- hot glazowii, though the same method is also em- 44 INDIA RUBBER, GUTTA PERCHA, BALATA. ployed in several regions in West Africa and on the mainland of India. In Ceara the operation is conducted as follows : The tree is tapped when about three years old, that is, when the trunk lias a diameter of about 4J to 5 inches. After cleaning the ground around the tree and spreading banana leaves for catching escaping milky juice, the Seringueiro makes in different places and in various directions slits in the bark from the foot of the tree up to a height of about five feet. The latex of Manihot being of much greater consistency than that of Hevea and Micranda, it exudes very slowly and seldom reaches the ground, most of it coagulating in the shape of long tears upon the bark of the tree, similar to resin on our trees. To allow it to dry, it is permitted to remain several days on the tree, when it is taken off in strips, folded to- gether or rolled into a ball, and without further preparation, it is thus brought into commerce as Ceara scraps. The rubber collected at the commencement of the harvest is of a blonde color, and represents the best quality. The second quality is of a darker brown color, and is gathered when the rainy season begins. The rubber collected at the foot of the tree consti- tutes the third quality, and is mixed, partly acci- identally and partly intentionally, with earth and ;sand. The loss in working it frequently amounts to Wore than 50 per cent. It is scarcely to be wondered at that rubber thus prepared contains a considerable quantity of min- RAW MATERIAL. 45 era! and vegetable constituents which considerably decrease its value. Ceara rubber has a beautiful amber color and is nearly transparent. The latter remarkable property, which, according to Morellet, is not possessed by any other variety of rubber, is claimed to be due to numerous holes in the interior of the mass through which the rays of light refract. Ceara rubber has a strong odor, which becomes decidedly disagreeable on exposing the product to moist heat. The pure article gives in working 75 to 80 per cent, of rubber, and is quite resistant. There would be a larger demand for Ceara rubber if it were prepared with greater care and not adul- terated by the addition of earth and other sub- stances. The latex of Manihot is at least equal to, and perhaps superior to that of Hevea, as it contains fewer nitrogenous substances which produce fermen- tation, and considerably less water. However, the industrial result of pure rubber is only 75 to 80 per cent. Furthermore, Ceara scraps are difficult to keep, as in consequence of their content of sub- stances producing putrefaction they require to be stored in a cool, dry place. While the treatment of the latex of Manihot, on account of its greater con- sistency, presents greater difficulty than that of Hevea, an improvement in the quality of the rub- ber might be attained by more suitable manipula- tion. Instead of allowing the milky juice to trickle down the trunk of the tree, it might be caught in cups and immediately mixed with alkaline water, it mixing in a fresh state better with this than with 46 INDIA RUBBER, GUTTA PERCHA, BALATA. pure water. In this manner the latex would be kept liquid for some time and fumigation might be employed for its coagulation. In Ceara, experiments of this kind have been made with excellent results, but unfortunately the natives will not listen to any- thing new, and continue their old, more rapid and less laborious method of preparation. The Manihot grows upon the steep granite rocks of Brazil and yields only small quantities of very thick milky juice, but the tree flourishes also in the plains and in moist soil, in which case the latex is thinner and more abundant and could be readily subjected to the above-mentioned treatment. Coagulation by skimming after the addition, of the same quantity of water, and a shorter or longer rest. This mode of separation is employed in Bahia with the latex of Han am tia, in some regions of Nicaragua and Central America with the latex of ( 1 1-12 Caching. I Water, 11.28 drachms. Mix the two solutions before use. With slight agitation, the above quantity effects the instantane- ous coagulation of one quart of milky juice. 54 INDIA RUBBER, GUTTA PERCHA, BALATA. In most cases a solution composed of 1 : 60 of the first and 1 : 30 of the second acid will be sufficient, but allowance must be made for the fact that coagu- lation is affected by the temperature, the hygrome- tric condition of the air, time of day, etc. For the coagulation of 1000 quarts of milky juice, two quarts of sulphuric acid and four quarts of phenol are required, and hence the expense of the operation is very small. From the quantity of milky juice above men- tioned, about 220 pounds of Para rubber are ob- tained, which is dry, hard, resistant, solid and of good appearance, which proves the availability of this method. From what has been said it will be seen that the latex of Hevea is not affected by some reagents which produce coagulation of the milky juice of other plants. Further, that the experiments to find in addition to the old method of fumigation, new processes of preparation are not promising, and the less so as experience has shown that rubber prepared by the addition of any kind of solution decreases in value." Rousseau's conclusions will no doubt be accepted as correct. The excellent quality of Para rubber is due to the care exercised in its preparation, and to abandon the method would unavoidably cause con- siderable loss. Beside, the antiseptic effect of phenol appears very doubtful. Creosote alone can effect complete sterilization, and only when USCM! after every layer, and under the influence of moderate heat. RAW MATERIAL. 55 Chemical disintegration by the addition of vegetable (igcnts. This method is in use in Madagascar, Gam- bia, Peru, Guatemala and Nicagarua. In some cases a vegetable acid is added and in others an in- fusion, the chemical composition of which is not de- finitely known, but the action of which is very likely more or less due to the presence of a vegetable acid. With the above mentioned African varieties of rubber, coagulation would seem to be effected by means of citric acid. Morellet says : " In examin- ing Madagascar rubber, grains were frequently found which were recognized as seeds of Aurantiacesz. It was at first difficult to understand how these ^eeds got into the rubber, but as they were found too fre- quently to allow of their presence being ascribed to accident, the conclusion was reached that the juice of Aurantiacese which contains citric acid was used for coagulation. This conclusion was later on con- firmed by persons who had traveled in those regions." Cousin asserts that while residing in Casamanza he had obtained by this method an amber-colored rubber, which was nearly transparent, of remarkable elasticity and durability. However this assertion is open to doubt, because while vegetable acids have the same defect as mineral acids of producing coagu- lation too rapidly, they are besides a natural breed- ing place of all kinds of microbes which produce putrefaction. This opinion is also confirmed by the fact that the use of citric acid for coagulation has been almost entirely abandoned in Madagascar, and sulphuric acid substituted for it. In Peru the co- 56 INDIA RUBBER, GUTTA PERCHA, BALATA. agulation of Hancornia latex is occasionally effected by means of a vegetable juice obtained from a climb- ing plant called by the natives Sachacamote. In Guatemala and Nicaragua the latex of Castilloa is treated in a similar manner. Coagulation is effected by an infusion of the root of Ipomcea bona nox which is widely distributed throughout Central America. In fact the milky juice is disintegrated by an or- ganic acid not definitely determined, but later a resin is found in the rubber which not only decreases the industrial yield but is difficult to remove and trou- blesome in manufacturing. On the other hand the same latex with different treatment yields a very elastic, strong and profitable rubber. Coagulation by a combination of natural or artificial heat with chemical disintegration. In Gambia (Casa- manza, Ivory Coast) the method employed with Valea and other climbing plants is as follows : The rubber gatherer makes a slight incision in the plant and then bruises the bark somewhat. Every bruise is rubbed with salt water and the incisions, which are about If to 2 J inches long, are arranged so that there is an interval of about four inches between them. The latex immediately exudes as a thick white liquid. Under the influence of the salt solu- tion the separation of serum and rubber takes place immediately, the globules of rubber running together and forming small lumps. The gatherer then takes a little rubber from each incision and combines these particles to a ball in his hand. But as the mass is very viscous, each portion neverthe- RAW MATERIAL. 57 less remains connected with the incision from which it exudes, so that a thread of rubber extends from each incision to the hand of the workman. The latter commences now to roll these threads, which are constantly formed by the uninterrupted exuda- tion of latex, into a ball. In consequence of the ex- tension and subsequent pressing between the fingers, the interior threads stick together as soon as they are covered by fresh threads, and the formation of th reads is visible only on the outside, and unwinding of the ball is impossible. The bruises must of course, from time to time, be moistened with salt water. The rubber thus obtained is at first nearly white, but becomes darker in time and acquires a reddish color. The weight of such balls varies between 9 and 28 ounces, though some weighing over 4J pounds are also brought into commerce. Since the workman cannot hold these large balls between his fingers, to roll them up, he lies down on his back, places the ball upon his body, holds it with one hand and con- tinues rolling until the plant is exhausted (Chapel). This method, by which natural and artificial heat, together with a powerful antiseptic, act uninterrupt- edly upon very small quantities of rubber, can be highly recommended, especially where, on account of local conditions or the constitution of the latex, fumigation is not possible. Every single thread is also exposed to the air and the heat of the hand of the workman, which promotes the evaporation of the serum. To be sure the operation is rather labor- 58 INDIA RUBBER, GTJTTA PERCHA, BALATA. ious. This method has another great advantage, namely that the product obtained is perfectly pure, it containing no vegetable or mineral admixture, ex- cept such as the workman intentionally adds. How- ever, by doing so he hurts himself most, because if the trader's suspicion is once aroused, it becomes difficult and frequently even impossible to sell the product. The various methods of coagulating crude rubber have now been described, and the result of experi- ence and experiments up to the present time may be summarized as follows : 1. In choosing the method of coagulation the den- sity of the milky juice must be taken into consider- ation. Vahea and Manihot yield thicker latex, and Hevea, Castilloa, Landolphia and Ficus, a more fluid one. Hence it would be incorrect to treat both kinds in the same manner. 2. Care must be had to produce rubber containing as little water and substances producing fermenta- tion as possible. Further, efforts should be made to keep the rubber free from foreign substances, in- troduced either accidentally or intentionally, as such admixtures, independent of decreasing the value of the product, always give rise to suspicion of fraud. In this respect two methods can be especially re- commended, namely, coagulation by fumigation and coagulation by artificial or natural heat with the addition of common salt. 3. The use of mineral and vegetable acids, as well as alum, and the addition of water, no matter in what form, always injures the quality of the pro- duct, and should, therefore, be avoided. RAW MATERIAL. 59 4. The shape in which rubber is stored is of im- portance. It has been observed that rubber keeps less well the larger the separate pieces are, especially when other fluids have been used in its preparation. This is readily explained, because the greater the surface presented the more moisture will evaporate, and the quality of the product is improved by dry- ing out and the formation of putrefaction prevented. 5. The mixing of different kinds of milky juice should be avoided, since the inferior latex will in- jure the better kind so that the product becomes of less value and the quality is more or less altered. 6. A knowledge of the chemical composition of every kind of latex would considerably contribute towards determining the exact method to be used in every case ; but unfortunately sufficient information in this respect is lacking, and it would be of great benefit to the rubber industry if chemists and nat- uralists would devote their attention to this subject. Adriani has endeavored to give an exact analysis of the latex of the Indian Ficus, and below the com- position of Hevea latex will be given as accurately as possible, but regarding the composition of the milky juice of other rubber plants information is wanting. Such information, however, would be of great use not only in choosing the best mode of coag- ulation, but also for storing the different varieties of rubber. 7. A better knowledge of the milk vessels, their arrangement and development in reference to the other organs of the bark, would also be desirable. 60 INDIA RUBBER, GUTTA PERCHA, BALATA. But little attention has been paid to this subject, and such study would give valuable hints regarding the quality *and treatment of rubber. Morellet has microscopically examined the bark of a few rubber plants and it would be well if his example were fol- lowed and the research extended to all rubber plants. Chemical and Physical Properties of Crude Rubber. Crude rubber as brought into commerce, being the inspissated or dried sap of certain varieties of plants, it will be necessary to consider first the fresh milky juice as it exudes from the plant, and for this purpose that of Hevea brasiliensis, being more or less typical, may be selected. It is a fluid which to the uaked eye appears white, but in reality it is color- less, or at the utmost has a slight amber-color tinge. It contains a quantity of globular bodies with an average diameter of 3.5 micromillimeters.* These globules are the actual rubber, and though colorless themselves, they impart by their diffusion to the entire fluid a milk-white appearance. The fresh latex of Hevea is odorless, but by expo- sure to the air it acquires, by the action of oxygen, an odor of methylamine,t which is found in all varieties of rubber not fumigated for the purpose of sterilization. The Para varieties of second quality, which consist of a mixture of fumigated and non- * One micromillimeter is the thousandth part of a milli- meter. f A colorless gas, having an ammonincnl and slightly fishy odor. RAW MATERIAL. 61 fumigated rubber, also show this peculiar odor. The taste of fresh Havea milky juice is not pro- nounced, it being rather agreeable and sweetish than disagreeable and bitter. Its specific gravity is diffi- cult to determine, it being affected by many acci- dental influences, but as a rule milky juice of less specific gravity is richer in elastic mass. The spe- cific gravity of typical latex of Hevea brasiliensis, at a temperature of 58-F. is about 1.019, with a con- tent of about 32 per cent, of rubber. The chemical composition of the latex of Hevea hrasilienxis as it exudes from the tree is as follows : Elastic constituents . . 32 per cent. Organic, nitrogenous con- stituents . . . 2.30 " " Mineral salts . . . 9.70 " " Resinous constituents . traces. Slightly alkaline water . 55-56 per cent. The chemical and physical properties of crude rubber also show considerable variations according to its origin, mode of obtaining it and subsequent treatment. The better qualities have a more or less characteristic odor, that of fumigated varieties being not disagreeable and resembling the odor of smoked bacon. On the other hand, non-fumigated varieties and those of inferior quality containing water have frequently a disagreeable, and in many cases ah offensive odor. The specific gravity : is 0.92 to 0.96. Crude rubber consists chiefly of a mixture of hy- drocarbons, and according to some analyses it has the formula C 4 H 7 ,or C 6 H 10 , or C 6 H 8 . However, 62 INDIA RUBBER, GUTTA PERCHA, BALATA. according to the most recent researches it is composed of C 45 H 36 . While this may be of little interest to the practical man, some varieties of rubber contain certain substances which deserve attention. When rubber is treated with alcohol certain com- binations are dissolved and are deposited in the form of crystals after the evaporation of the alcohol. The crystals dissolve readily in water, but there is considerable variation in their properties. By treat- ing these combinations with solution of hydrogen iodide, they split into new bodies and not into fer- mentable varieties of sugar. The bodies soluble in alcohol have been called dambonite, bornesite and matezite, the first being found in African rubber, the second in Borneo rubber and the last in Madagascar rubber. Their composition is as follows : Dambonite, C 4 H 8 O 3 Dambose, C 3 H 6 O 3 Bornesite, C 7 H U O 6 Borneodambose, C 6 H,. 2 O 6 Matezite, C ]0 H 20 O 9 Matezitedambose, C 9 H 18 O 9 Although rubber is distinguished by its great chemical indifference, it is very sensitive to certain influences, especially to light, and oxygen and sul- phur have great effect upon it. That a change in the substance of rubber is pro- duced by light, is shown by the following experi- ment : If rubber be exposed to the direct rays of the sun and then pressed upon a lithographic stone, the portion of the latter brought in contact with it will take and hold printing ink, while rubber not ex- posed to the sun fails to produce this effect. KA\V MATERIAL. 63 If rubber be stored for a considerable time sev- eral years where it is exposed to the air, it suffers considerable change, at least on the surface. If such rubber be treated with a solvent, for instance benzene, a body is dissolved in the latter which re- mains behind after the evaporation of the solvent and shows the physical properties of a resin very rich in oxygen and not soluble in carbon disulphide nor in oil of turpentine both solvents of rubber. This proves that by long-continued exposure to the air, partial oxidation of the rubber has taken place. According to C. A. Burghardt, rubber gradually oxidizes, while a resin readily soluble in alkalies is formed which contains 27.3 per cent, of oxygen and besides a mass insoluble in alkalies and benzene is formed which contains up to 20 per cent, oxygen. Fresh vulcanized rubber contains three per cent, of- the first resin, but none of the latter. By coaling rubber with oil, especially olive or palm oil, its destruction is accelerated, because these bodies promote the action of oxygen. Rubber brought in contact witli copper or copper combina- tions is also rapidly ruined. Rubber to which in vulcanizing an excess more than 2 to 2J per cent. of sulphur has been added is quickly destroyed by the sulphuric acid formed from the sulphur. The content of water in good rubber amounts to only 0.5 per cent., while old rubber articles which have become hard contain 5 to 10 per cent., which escapes completely only at 248 F. When rubber becomes hard and brittle, a chemi- 64 INDIA RUBBER, GUTTA PERCHA, BALATA. cal change evidently takes place, the content of carbon decreasing, as shown by the following an- alyses by Burghardt : I. II. III. IV. V. Carbon .... 77.91 72.53 70.43 65.09 64.00 Hydrogen . . . Sulphur ... Oxygen .... 10.33 5.15 6.61 11.31 1.97 14.19 10.59 3.14 15.84 10.00 1.95 22.96 9.26 2.28 24.46 No. I was good material, but contained too much sulphur ; Nos. II, III and IV were more or less brittle, and No. V very hard and brittle. Neither cold nor warm water dissolves rubber, but boiling water extracts from some varieties a resin-like substance. In warm water it becomes very soft and swells up considerably, dark pieces becoming lighter and the whole mass more suscept- ible to solvents; but on being exposed to the air for some time, the normal condition is restored. The pale color of light, opaque varieties of rubber is due to 4 a content of water ; after drying, the} are trans- parent and dark. Rubber is capable of absorbing as much as 18 per cent, of its weight of water, its volume at the same time increasing to as much as 10 per cent. Behavior towards sulphur. The behavior of rub- ber towards sulphur is of great interest to the man- ufacturer. Brought in contact with melted sulphur, it absorbs it very freely and, according to the quan- tity of sulphur used and the temperature to which the mixture is heated, two substances are produced showing very different properties, RAW MATERIAL. 65 If rubber is treated with a small quantity of sul- phur and the mixture heated for a short time, a gray substance is obtained possessing great elasticity, which does hot vary much even under changes of temperature. The product thus formed is known as vulcanized rubber or 'vulcanite. But if rubber is treated with a large quantity of sulphur at a high temperature for a considerable time, it gradually acquires properties entirely differ- ent from its original ones. It is black, possesses but little elasticity, and as regards its physical proper- ties, may be best compared with horn. This sub- stance is known as hard rubber or ebonite. Behavior towards solvents. Solutions of rubber are of great importance for many industrial purposes, the manufacture of water-proof tissues, of rubber lacquers and varnishes, etc., depending on them. The behavior of rubber towards solvents is different from that of most substances, which are either solu- ble or insoluble, and in this respect it very much re- sembles resins. Although not soluble by certain agents, it will swell up when brought in contact with them, and thereby acquire the property of being soluble in many substances to which other- wise it is entirely indifferent. In many solvents, for instance, in a mixture of alcohol and carbon di sulphide, rubber swells up to thirty times its original volume, and in preparing solutions of it, this must be taken into considera- tion. Among the substances capable of dissolving rub- 5 66 INDIA RUBBER, GUTTA PERCHA, BALATA. ber in the actual sense of the word may be men- tioned : Ether, benzene, oil of turpentine, essential oils, and tar oils in general, as well as caoutchoucine, an oily product obtained by the destructive distilla- tion of rubber. Fat oils heated to a high tempera- ture will also dissolve it, but it is questionable whether the resulting products can be actually con- sidered as solutions of unaltered rubber. However, the substances named above are not capable of holding the entire mass in solution, and can absorb only a certain proportion of it. To ob- tain the best solutions, the rubber, as well as the solvent, should be as free from water as possible, and two solvents should be used, allowing the rubber to swell up in one and then dissolving it in the other. Some experiments have been made as to the solu- bility of different varieties of rubber, the solvents used being entirely free from water and the rubber having been previously dried for one week over sulphuric acid. These experiments, as shown by the results given below, prove that different vari- eties are soluble in various proportions. Of 1 00 parts of dried rubber were dissolved : In carbon disulphide . 65 to 70 parts. In benzene . . . 48 to 52 " In oil of turpentine . . 50 to 52 " In caoutchoucine . . 53 to 55 " In ether . . . . 60 to 68 " If the solutions are allowed to evaporate, a color- less mass of considerable elasticity is left behind, which, however, does not possess all the properties RAW MATERIAL. 67 of rubber, its behavior differing from the latter, especially when subjected to heat. According to T. F. Hanausek : Ceara Nigger- Sierra rubber, head. Leone. Parts. Parts. Parts. 100 parts of ether ...... dissolve 2.6 3.6 4.5 " oil of turpentine . " 4.5 5.0 4.6 " " chloroform ... 3.0 3.7 3.0 " benzene . . . . 1.5 4.5 4.0 " carbon disulphide " 0.4 The portion of the rubber which remained behind after repeated treatment with the above-mentioned solvents, showed a brown color similar to that of the product originally used, possessed little elasticity but considerable tenacity. When examined with a microscope, immediately after treatment with the solvent, it appears like a wide-meshed net, but in drying it contracts considerably. As has previously been mentioned, to effect a complete solution of rubber requires certain manip- ulation, and may be best done as follows : Allow the rubber to swell up in carbon disulphide, which is most rapidly effected in a closed tank in a moder- ately warm place. Then add 10 parts of absolute alcohol for every 100 parts of carbon disulphide used. Solution will be complete in a few days, and by allowing the mass to stand quietly for a sufficient length of time, all foreign admixtures will settle on the bottom. By mixing the solution with a large quantity of alcohol, the rubber is again precipitated in a spongy 68 INDIA RUBBER, GUTTA PERCHA, BALATA. form, while the foreign substances remain in solu- tion. By pouring off the brownish solution from the precipitate and repeating the same operation several times, the rubber is obtained free from col- oring matter, as an entirely white mass, or showing at the utmost only a slightly yellowish color. The use of carbon disulphide as a solvent is, how- ever, objectionable, on account of its great volatility and also its poisonous fumes, and oil of turpentine is, therefore, recommended as a substitute for the preparation of rubber solutions. But the ordinary commercial oil of turpentine always contains a. con- siderable percentage of water, and does not effect complete solution. Hence, for the preparation of large quantities of solution, it is advisable to free the oil of turpentine from water, which may be effected in various ways. The simplest plan is to pour it, together with about 10 per cent, of its weight of sulphuric acid, into a tank, cover the latter tightly, and let it stand quietly until the solve.it is to be used. The sulphuric acid forms a sediment on the bottom of the tank, from which the oil of turpentine can be readily drawn off. In place of sulphuric acid, fused calcium chloride can be used with equal success. For the treatment of larger quantities of oil of turpentine, it is advisable to rectify it over quick- lime and to pass the vapor, before it condenses, through a nearly red-hot pipe. By this process, the character of the oil of turpentine is much improved, and it is much better adapted as a solvent. RAW MATERIAL. 69 The solution of rubber is readily effected by cut- ting it into small pieces and placing them in linseed oil heated to a point, when it throws out heavy vapors and is in a state of ebullition. But it is scarcely possible that in a solution thus prepared there is any unaltered rubber, and it is very likely that it only contains products of decomposition of it. For certain purposes such solution is, however, very useful. When applied in a thin layer to an article and exposed to the air, it dries to a transpar- ent layer distinguished by great tenacity. Caoutchoucine, or oil of caoutchouc, which, as previously mentioned, is obtained by destructive distillation of rubber, has been recommended as a solvent without, however, being especially suitable for the purpose. Its power of dissolving rubber is only slightly greater than that of anhydrous oil of turpentine, and the cost of producing it is compara- tively great. It would seem that for practical purposes the most suitable solvents are carbon disulphide in com- bination with absolute alcohol, and anhydrous oil of turpentine. To be sure, benzene and coal-tar oil are also good solvents, but they have the disadvan- tage that their disagreeable odor adheres for a long time and very tenaciously to the rubber. Lascelles recommends 92 per cent, benzene and 4 to 8 per cent, of eucalyptus oil as a solvent. In case solution is to be effected by means of carbon disulphide and absolute alcohol, it is advis- able for the manufacturer to prepare the latter him- 70 INDIA RUBBER, GUTTA PERCHA, BALATA. self, which may be done as follows : Bring 95 to 96 per cent, alcohol into a flask previously filled about one-fifth full with blue vitriol which has been heated to such a degree that the blue color has been changed to white. The vitriol absorbs all traces of water from the alcohol whereby it grad- ually reassumes its original blue color, while the supernatant alcohol has become entirely anhydrous, i. e., absolute alcohol. According to C. Fry's patented method solutions of rubber and gutta-percha can, it is claimed, be prepared with great facility if the solvent coal-tar oil or oil of turpentine is distilled with a small quantity of rubber or gutta-percha. The crude oil is brought into a still, and to each 11 Ibs. of it are added 6J to 9 ozs. of rubber or gutta percha. The solvent is distilled off, and the residue re- maining in the still used for producing coarser tissues. It is claimed that solvents prepared in this manner are best adapted for the oolution of rubber and gutta percha. If such be actually the case their superiority is very likely due to an admixture of decomposed products of rubber, many of them being excellent solvents of the latter. It has also been suggested to distil rectified spirits with rubber in the same manner as described, the dissolving power, it is claimed, being thereby con- siderably increased. However, since petroleum lias come into use for preparing rubber solutions, which will be referred to later on, and as carbon disul- phide and the light tar oils can be procured at very RAW MATERIAL. 71 low prices, the question as to solvents for rubber has lost much of the importance it formerly pos- sessed, and at the present time rubber solutions of any desired consistency are readily prepared. Behavior in heat. At 50 F. rubber is compara- tively solid, and not very elastic, at 96.8 F. it is soft and elastic to a high degree ; gradual increase of heat decreases the elasticity, and at 248 F. it liquefies and emits a peculiar odor. When it has been heated to the melting point it congeals on cooling to a mass, which remains sticky for a long time. If exposed to a still greater heat, it ignites and is consumed with a bright and sooty flame. But if treated at a high temperature in a closed vessel, that is, if it is subjected to destructive distil- lation, there is obtained, besides the coal which is deposited, a quantity of gas, and a fluid called oil of caoutchouc, which, as has been stated, is a sol- vent for rubber. The crude oil of caoutchouc (caoutchoucine) gained by destructive distillation, is a mixture of several combinations of hydrocarbons, some of which are characteristic of rubber, while others appear also in the destructive distillation of other organic substances. By heating rubber in vacuum to a temperature above 392 F. a mixture of isoprene, caoutchene and heveene is formed. Gladstone and Hilbert have adopted for these combinations the following compositions : 72 INDIA RUBBER, GUTTA PERCHA, BALATA. Rubber .... U C 6 C 4 H 16 Isoprene .... C 4 CH 8 Caoutchene .... C 4 C 6 H 16 Heveene . . . . n C 2 C 8 H 8 The following bodies have thus far been determined as being present in oil of caoutchouc: Eupione, buty- lene, caoutchin, caoutchene or dipentene, isoprcne and heveene. Caoutchin forms at 0.4 F. a white crystalline mass consisting of needles which at 14 F. fuses to a transparent oil and boils at 58.5 F. Isoprene is a water-clear, very mobile liquid which boils between 98.5 and 100.5 F. By the admis- sion of air it loses its fluidity, becomes sticky and absorbs ozonized oxygen with avidity. Eupione, butylene and isoprene are chiefly found in the por- tion of the distillate which passes over first, and must be collected in vessels thoroughly cooled off. The greater portion of caoutchene is found in the part of the distillate which passes over between 284 and 530 F. When pure it boils at 330.8 F., and, what is very remarkable, congeals only at a temperature below 40 F. It also absorbs oxy- gen with avidity. Heveene, which is contained in the last portions of the distillate passing over, is an amber-colored oil, of specific gravity 0.92 at 70 F. It boils at 599 F., does not congeal in the cold, has a slightly empyreumatic odor, an acrid taste, and consists of 86.11 percent, carbon and 14.02 percent, hydrogen. According to Bouchardat, 11 Ibs. of fresh Para rubber yield 8.81 ozs. isoprene, 70J ozs. caoutchene RAW MATERIAL. 73 (dipentene), and 21.16 ozs. heveene. There are formed besides, polyterpenes boiling at a higher temperature than heveene and only a small quantity of gases, carbonic oxide, methane and ethylene. Among the products of distillation, caoutchene and eupione are the most effective solvents. In the former rubber swells up very much and a consider- able quantity of it is dissolved by boiling, the solu- bility increasing in proportion to the percentage of eupione contained in the solvent. If oil of caoutchouc is to be prepared for use as a solvent, the receiver in which the products of distil- lation are collected must be thoroughly cooled so as to retain the very volatile eupione in the distillate, and, of course, the bottles in which the oil of caout- chouc is kept must be hermetically closed. Commercial Rubber. The varieties of crude rubber occurring in com- merce may, according to their origin, be arranged in three principal classes as follows : T 4 i i f South American rubber. I. American rubber^ I Central American rubber. II. African rubber / East African mbber I West African rubber. III. Asiatic rubber. IV. Australian rubber. In commerce these varieties are not always known by regular names, the separate kinds being some- times called after the province of their origin, though sometimes other regions yield the same kind of pro- 74 INDIA RUBBER, GUTTA PERCHA, BALATA. ducts, and sometimes after the shipping place or the city which is the center of trade for the respective variety. A brief summary of the best known vari- eties, including their commercial names, place of origin, form in which they are brought into com- merce, appearance, properties, etc., is given below : I. AMERICAN RUBBER. 1. SOUTH AMERICA : Fine Para; Seringa fina, called by the natives Bor- racha or Jebe. Origin : Amazon river, Brazil. Form : Biscuits or loaves ; weight of the pieces from the Lower Amazon, 6| to 11 Ibs.; from the Upper Amazon, 22 to 33 Ibs. Appearance : Dark brown to blackish. Cut surface : Darker towards the outside, whitish towards the inside. The separate layers can be recognized as leaves or skins. Odor : Like smoked bacon. Adulteration : Few foreign sub- stances ; sometimes mixed with the latex of Minu- sops elata, Marcandaruba. Moisture varies according to the time of gathering. Loss in ivorking : 10 to 15 per cent. Strong and elastic. The biscuits fre- quently bear the name of the factory. Entrefine Para ; \ fine Entrefine ; Grossa, Origin : Amazon river. Form : Biscuits or loaves, those from the Lower Amazon weighing from 6J to 11 Ibs. each, and those from the Upper Amazon 22 to 33 Ibs. each. Appearance : Dark brown to blackish. Cut surface : Very different from fine Para, the non- fumigated portions being dirty white, the fumigated ones brown amber color. Odor : Less pronounced than that of fine Para, it having an odor of methyl- amine. Adulteration : Few foreign substances, con- RAW MATERIAL. 75 sisting generally of bark. Moisture like fine Para. Loss in working: 15 to 20 per cent. Less strong than fine Para, The large loaves and^ biscuits of fine Para are cut up partly in the trading places and partly in Para, and all pieces not thoroughly fumi- gated, and containing streaks of non-fumigated rub- ber, are sorted out as entrefine. Nigger heads; Para Sernamby ; Sernamby de Bor- racha ; Sernamby de Jebe ; Cabeca de negro. Origin : Amazon river. Form : Comes into market either in large blocks or mostly in irregular pieces, the size of the hand, which, in consequence of solid packing, stick together. Appearance : Black. Cut surface : Yellowish white with black veins. Odor : Smells like methylamine ; sometimes mouldy. Adultera- tion: With sand and non-elastic, so-called dead rub- ber. Very moist. Loss in working : 20 to 40 per cent. Lacks resistant power. Virgin sheets or -Matto-grosso Para (Para blanc). Origin : Province Matto Grosso, Brazil. Form : Large loaves of regular shape, about two feet long, one foot wide and six inches thick ; smaller loaves of half the size. Appearance : Pale brown. Cat sur- face : Straw yellow, with greenish marbling, especi- ally on the edges. Loss in working : 15 to 30 per cent. Less strong than brown Para. Like Para, it is classed : Fine, J fine, Sernamby. Ceara scraps. Origin : Province Ceara, Brazil. Form : Small strips or tears rolled in a lump. In consequence of being solidly packed in a fresh state, the balls stick together and form blocks weighing 76 INDIA RUBBER, GUTTA PERCHA, BALATA. up to 330 Ibs. Appearance: Pale and dark brown amber color. Out surface: Pale amber color ; when extended, white and opaque. Odor: Very dis- agreeable, becoming more so by exposure to moist heat. Adulteration : Always mixed with vegetable matter, frequently also with sand. Up to 15 per cent, of moisture. Loss in ivorking : 20 to 25 per cent.; with inferior qualities mixed with sand, up to 50 per cent. Quite strong. The serum of Ceara rubber can be quite w T ell removed by mechanical pressure. Pernambuco (Mongabeira). Origin : Province of Pernambuco, Brazil. Form : Rectangular patches varying in size ; sometimes 5 feet long, 2 feet wide and a few inches thick. Appearance: Reddish orange-yellow with saline efflorescence. Cut surface : White to rose color. Numerous holes filled with serum containing alum. Loss in working : 40 to 60 per cent. Has but little elasticity ; flabby ; in little demand and sometimes is used only on account of its beautiful color. In time it becomes hard and brittle. Maranham. Origin : Province Maranham, Brazil. Appearance: Smooth, lustrous, no saline efflores- cence. Cut surface: White to rose color; acquires, on exposure to the air, a beautiful dark wine-red color. Loss in working : 25 to 30 per cent. Stronger and more elastic than Pernambuco. The serum contains sugar. BaJtia. Origin: Province Bahia, Brazil. Form: Irregular masses or large patches weighing up to . RAW MATERIAL. 77 110 Ibs. Appearance : Reddish-orange. Cut surface : AYhite to rose-color, holes with serum and frequently with non-coagulated latex. Adulteration: Wood, vegetables, sand, clay. Very moist. Loss in work- ing : 50 per cent. Of inferior quality ; in little demand. CartJiagcna (Esquebo). Origin : Columbia. Form : Large balls weighing up to 190 Ibs., formed of patches or strips which are folded together like Nicaragua scraps. Appearance: Black. Cut sur- face: Brownish, black, greenish, gray. Odor: Of methylamine and mould. Adulteration: Earth. Loss in work-ing: 25 to 60 per cent. It is quite in demand. The good quality is elastic, but that adulterated with earth is ven r dead. Ou/idad-BolivcLT, Columbia Virgen. Origin: Vene- zuela. Form: Like Para rubber. Appearance: Like Para. Cut surface : Like Para. Odor: Slightly fumigated. Adulterations: Often mixed with the sap of Massaranda and Pindar. Loss in ivorking : 15 to 20 per cent., according to quality. Resem- bles Para rubber and is often sold as such. Cayenne. Origin : French Guiana. Form, ap- pearance and cut surface: Like Para rubber. Odor : Slightly smoky. Adulteration : Quite pure. Loss in working: 15 to 20 per cent. Value equal to Para. Peru in slabs, also called caucho. Origin: Peru. Form : Large blocks, or like fine Para. Appearance : Deep black, surface granular. Cut surface: Yellow ; becomes in time slate-color; very porous. ' Adul- 78 INDIA RUBBER, GUTTA PERCHA, BALATA. teration : Much sand and water. Loss in working : 25 to 30 per cent. Very elastic and highly valued, though the color is not liked. By boiling in water the rubber loses its black color and becomes dirty- white. Peruvian balls, Sernamby de Perou, Sernamby de CaucJw. Origin: Peru. Form: Like niggerheads. Appearance : Deep black ; surface granular. Cut surface: Yellow; becomes in time slate-color ; very porous. Loss in working : 25 to 30 per cent. Ser- nambillo (waste) is better than niggerheads, as it contains less water and is less porous. Guayaquil (in patches). Origin : Ecuador. Form : Large patches up to 3 feet 3 inches in length, 2J feet wide, and about f inch thick. Appearance : Blackish. Cut surface: Black-green, very moist, with many water bubbles. Adulteration: Very im- pure ; earth and vegetable matter ; much water. Loss in working : 20 to 35 per cent. Partly very elastic, and partly adulterated with earth, and dead like Carthagena rubber. 2. CENTRAL AMERICA. Colon and Panama. Origin: Ecuador, Columbia. Form: Strips about 4 inches m diameter and up to 10 feet in length. Quality similar to Carthagena rubber. Mexican and oth(r Central America and West Indies sheets. Origin : Vera Cruz, Taumapilas, Tabasco, Guerero, Baraca, Repic Chiopas. Form: Sheets from 0.39 to 1.57 inches thick, and 2x 2J inches in length and width ; sometimes balls (marbles) 2 to 2J inches in diameter. Appearance : Black. Cut RAW MATERIAL. 79 surface : Black, brown, yellow-greenish. In cutting a sheet a brownish liquor sometimes runs out. Adulteration : Sand, earth, leaves, sometimes splin- ters of wood. Loss in working : 12 to 15 per cent. Extraordinarily strong. Guatemala. Origin: Guatemala. Form: Sheets. Appearance : Black. Cut surface : Black, partly yel- low-greenish, partly brown ; contains a thick fluid (non-coagulated rubber). Odor: Very character- istic. Adulteration: Dirt, bark, earth. Loss in work- ing : 25 to 45 per cent. Partly strong like Guaya- quil, partly softer. Nicaragua, Mexican, Ecuador and West Indian scraps. Origin : Nicaragua, Mexico, San Salvador, Ecuador. Form : Either sausages as thick as an arm or balls of at least the size of a head. Sometimes also cubes 2 to 2J feet long. The scraps are always composed of folded or rolled strips, waste of sheets and spon- taneously dried drops. Appearance: Blackish. Cut surface : Usually blackish and lustrous ; sometimes yellowish, but soon turns black on exposure to the air. Adulteration : Slight moisture, some cork, sometimes sand. Loss in working: 10 to 15 per cent. Very much in demand ; classes next to fine Para. II. AFRICAN RUBBER. Senegal and Bissao balls. \ Origin : Senegambia. Soudan, Bissagos Islands. ; Form : Partly balls, partly sheets. Appearance : Black, brown. Cut surface: Rose color, white. \Adulteration: Much moisture, sand, bark, dirt. Loss \in working: 25 to 50 per cent. Partly very strong, and quite in demand. 80 INDIA RUBBER, GUTTA PERCH A, BALATA. Gambia balls. Origin: Senegambia, Bathurst, Bissagos Islands, Soudan. Form: Balls. Appear- ance: Brownish, white, and black. Cut surface: White with a slight tinge of rose-color. Adultera- tion : Moisture, sand, small quantity of bark. Loss in working : 20 to 50 per cent. Pure, dry balls are in good demand ; second quality is not much liked. Casamanza (Boalam). Origin: High table-land on the right-hand bank of the Casamanza river, Senegambia. Form: Like Senegal rubber. Appear- ance: Dark brown. Cut surface: Grey shading into cream-yellow and reddish ; holes with much sand. Odor: Bad. Adulteration: Much earth and sand. Loss in working : 40 per cent. Not much in demand. Is chiefly brought into commerce in March. Casamanza (Gambia). Origin: Left-hand bank of the Casamanza river. Form: Balls weighing 10 to 28 ozs., and even up to 4 Ibs. Appearance: At first white, afterwards red-brown. Cut surf ace : Concen- tric layers; color, red-brown to white; Avhite pre- dominates, but on exposure to the air, it gradually acquires the red-brown tone of the surface. Some- times concentric veins, black, white and rose : color. The rubber prepared by chemical disintegration, by the addition of vegetable matter, is of a pale amber color. Adulteration : Small quantity of foreign sub- stances ; quite moist. Loss in ivorking : 20 to 40 per cent., according to quality. Quite strong. This rubber would be excellent, if it were not mixed with other varieties of latex, the black rubber contained therein being very sticky, and having an injurious effect upon the paler rubber. RAW MATERIAL. 81 Sierra Leone Niggers, Massai Niggers. Form : Balls. Appearance: Red, red-brown, white. Cut surface; Red and glassy brown, white. Odor: None. Adul- teration: Partly very pure, partly mixed with bark and earth ; partly dry, partly moist. Loss in work- ing: 10 to 35 per cent. Red, dry balls are highly valued ; soft and moist ones are not liked. Sierra Leone twist : Appearance: Brown. Cut sur- face : White. Adulteration : Partly very pure, though frequently adulterated in the interior with earth and bark and only covered with good strips. Loss in working: 18 to 35 per cent. Strong and highly valued. Liberia. Origin: Liberia. Form: Balls and lumps. Appearance: White, brown, black. Cut sur- face: Of the balls, white and rose color; of the lumps, green, yellow and white. Odor: Of the balls, slight; of the lumps, very bad. Adulteration: The balls are pure, but quite moist ; the lumps very moist. Loss in working: 20 to 40 per cent. Grand Bassam. Origin: Ivory Coast. Form: Lumps. Appearance : Black. Cut surface : Dark green, partly pale. Odor : Bad. Adulteration : Quite pure, but moist. Loss in working : 20 to 30 per cent. Much in demand. Accrah. Origin : Gold Coast. Appearance: Brown, black. Cut surface: Yellow, brown. Odor: Very bad. Adulteration: Moist; sometimes mixed with earth. Loss in working : 30 to 45 per cent. A good quality of this rubber is much in demand on account of its purity, but the soft article is not 82 INDIA RUBBER, GUTTA PERCHA, BALATA. liked. Accrah biscuits pressed on the coast are no longer found in commerce. Niger Niggers. Origin : Niger Territory. Form : Compressed balls. Appearance: White, red. Cut surface : White ; root-rubber, partly red. Odor : Slight. Adulteration : Partly pure, but moist ; the root-rubber contains much bark. Loss in working : 20 to 45 per cent. The white balls are strong, and in demand ; the root-rubber is resinous and soft. Gaboon Balls. Origin : French Congo. Form : Large and small balls. Appearance: Black and gray. Out surface : Of the large balls, rose-color, blue and red ; of the small ones, grey, white and green. Odor: Bad. Adulteration: Bark, sand, very moist. Loss in working : 27 to 40 per cent. The large balls are strong and highly valued, but the small ones are soft and in little demand. Gaboon Tongues. Form : Small, oblong balls. Cut surface: White and gray. Adulteration: Sandy on the outside, moist, partly calcareous. Loss in working : 35 to 45 per cent: In little demand. Kassai rouge. Origin : Congo State. Form : Small balls, ten of them being stuck together so as to form a short pig-tail. Appearance: Ked. Adul- teration : Very few impurities. Loss in working : 6 to 8 per cent. Very sinewy. Is considered the best quality of the Congo varieties. Kassai noir. Origin : Congo State. Form : Pig- tails. Appearance : Black. Adulteration : Fre- quently mineral and volatile substances. Of less value than Kassai rouge. RAW MATERIAL. 83 Kassa'i noir in balls. Origin : Congo State. Form : Pieces of irregular size stuck together to form balls. Appearance : Black. Adulteration: Neither sand nor wood, but considerable quantities of volatile, fermenting substances. Kassa'i strips. Origin : Congo State. Form : Balls stuck together. Adulteration: Volatile, fer- menting substances. Quite strong. Upper Congo (common). Origin : Congo State. Form: Balls stuck together. Adulteration: Bark and about 8 per cent, water. 'Loss in working : About 15 per cent. Strong. This is the variety first imported from Congo. Upper Congo (white). Origin: Congo State. Form: Balls. Cut surface: White. Adulteration: Very pure, 6 to 8 per cent, water. Very strong. Equator. Origin : Congo State. Form : Balls stuck together. Adulteration : But few impurities, 5 to 7 per cent, water. Strong, good quality. Lopari. Origin: Congo State. Form: Balls. Adulteration : Volatile and fermenting substances. Very elastic ; as much in demand as Equator. llusira. Origin : Congo State. Form : Balls. Highly valued, almost as much as Equator. Aruwimi, Mongala, Bumba. Origin: Congo State. Form : Balls weighing up to 11 Ibs. Odor: Very bad and penetrating. Adulteration : Up to 35 per cent, of fermenting substances. Loss in working : Large. Quality, good. Uelle. Origin : Congo State. Form : Sheets weighing up to 22 Ibs. Appearance: White. Adul- 84 INDIA RUBBER, GUTTA PERCH A, BALATA. teration : Quite pure ; volatile, but only exception- ally fermenting, substances. Longer Congo (thimbles). Origin : Congo State, Angola. Form : Square cut pieces. Appearance : Quality I., red and black ; Quality II., black and reddish. Cut surface: Quality I., red and black; Quality II., red. Adulteration: Quality I., pure, sometimes sandy ; Quality II., contains bark, and in some instances earth. Loss in working : I., 12 to 20 per cent ; II., 27 to 45 per cent. Quality I., strong though partly resinous; II., when dry much in demand, but not liked when wet. Luvituku. Origin : Lower Congo. Form : Balls. Composition and quality like Congo thimbles. Loanda thimbles. Origin: Angola. Form : Thim- bles or cubes, 0.19 to 1.18 inches in size. Appear- ance: Slate-gray. Cut surface : Lustrous, slate-gray with white dots. Odor : Offensive, like dry Congo rubber. Adulteration : No foreign substances, though recently attempts at adulteration have been made. Loss in working : 15 to 20 per cent. Inclines to become soft and smeary, and should be kept in a cold room. Loanda Niggers. Origin : Angola (Loanda). Form : Balls strung together in chains. Appearance : Qual- ity I., red and black; II., reddish. Cut surface: I., red and black; II., red. Odor: Slight. Adultera- tion : Quality I., pure and dry ; II., much bark, and in some cases sand. Loss in working: L, S to 15 per cent., II., 20 to 27 per cent. Quality I. is strong and much in demand : Quality II., RAW MATERIAL. 85 strong, but quite in demand when dry and not oxi- dized ; resinous. Angola Niggers or Nigger-heads. Origin : Angola. Form: Balls of irregular form, 1.18 to 2 inches in diameter. Appearance : Reddish-brown. Cut sur- face : Reddish-brown, almost transparent towards the centre ; very soft, but becomes hard when ex- posed for a fe\v days to the air. Adulteration : Quite moist ; small quantity of portions of plants. Loss in working : 20 per cent. Less strong than Loanda Niggers; quite sticky. Benguela Niggers. Origin : Angola (Benguela and iMossamedes). Form: Balls strung together to chains ; also small sausages. Appearance : Reddish. Out surface : Red. Adulteration : Much bark. Loss in working : 20 to 25 per cent. When dry the rub- ber is much sought after, but the fresh article, pale inside, which readity oxidizes, is not in demand. Mozambique Marbles. Origin: Mozambique. Form: Small balls pressed together. Appearance: Black and reddish. Cut surface: Red, in isolated cases, white. Adulteration : Much bark ; partly sand ; moist. Loss in working : 30 to 40 per cent. Soft, of inferior quality ; root-rubber. Mozambique Balls. Origin: Mozambique, Ger- man East Africa. Form : Smaller and larger balls. Appearance : Brown and rose-color. Cut surface : Red, brown, rose-color, W 7 hite. Odor : None. Adul- teration : Quality I a I a is very pure and dry ; infer- ior quality contains sand and portions of plants, and is moist. Loss in Working : 8 to 35 per cent. The 86 INDIA RUBBER, GUTTA PERCHA, BALATA. best glassy balls which are cut piece by piece in their place of origin are much in demand on ac- count of their excellent quality and small loss in working. Inferior qualities are f also in demand. Mozambique Spindles. Origin : Mozambique. Form : Spindles. Appearance : Brown and red. Cut surface : Red and brownish ; in isolated cases, black. Odor: None. Adulteration: Bark and sand. Loss in Working: 12 to 27 per cent. When un- adulterated much in demand, as the rubber is very strong and the loss in working small. Madagascar, black. Origin : Madagascar. Form : Large round pieces. Appearance : Black. Gut sur- face: White, rose-color, yellow, green. Odor: Offensive. Adulteration : Earth, portions of plants, very moist. Loss in working: 30 to 45 per cent. Suitable for the manufacture of hard rubber. Madagascar, pinky. Appearance: Brown and black. Out surface : Rose-color, white. Adultera- tion: Pure, but moist. Loss in working: 25 to 40 per cent. Highly valued. Not very strong, but elastic. Madagascar Niggers. Form : Large balls. Ap- pearance : Black and yellow. Cut surface : Brown- ish, white, black and yellow. Odor: Slight. Adulteration : Dry, but generally much adulterated with earth. Loss in working : 20 to 60 per cent. The yellow West Coast Niggers are frequently very soft, but sometimes, like the East Coast Niggers, are very strong, and are then highly valued. III. ASIATIC RUBBER. Assam. Origin: North RAW MATERIAL. 87 West Bengal (Brahmapootra). Form: Lumps weighing up to 5J ozs. which adhere firmly to the cover as this rubber becomes rapidly viscous and smeary. Appearance: Brown. Cut surface: Dark, sometimes gray, sometimes reddish with white nearly transparent patches. Adulteration: Moist sand, wood, earth. Loss in working : 25 to 40 per cent. Was' formerly much liked, but is now less highly valued because it has deterioarated in qual- ity. It is disappearing from the' market. Rangoon. Origin: Burma, Cochin-China, Anam, Tonkin. Form: Irregular masses. Appearance: Very dark brown. Cut surface : Lustrous, white, red and black marbled. Adulteration : Always con- tains wood. Loss in working : 20 per cent. Less valued than the preceding variety. Penang. Origin: Sumatra and other Sunda islands. Form: Large bisected lumps and balls. Appearance: Red, brown. Cut surface: Red, rose- color, whitish. Adulteration: Wood, small quantity of earth, partly moist. Loss in working: 15 to 30 per cent. A good dry quality is highly valued ; the moist, sticky article is not in demand. Ceylon. Origin : Ceylon. Form : Irregular cubes about 4 inches large. Appearance: Black. Cut surface: Dark brown, pale brown, and transparent. Adulteration: Sand, earth. Loss in working: 20 to 25 per cent. Quite strong. Java and Padong. Origin : Java, Sumatra, and other Sunda islands. Form : Large bisected lumps and balls. Appearance : Red, brown. Cut surface : 88 INDIA RUBBER, GUTTA PERCH A, BALATA. Red, glassy, rose-color, white. Odor: Slight. Adul- teration: Wood, small quantity of earth, partly moist. Loss in working : 12 to 30 per cent. Good, dry ware is much in demand ; the moist, sticky article is not valued. Borneo. Origin : Borneo. Form : Large lumps, flat pieces, and balls. Appearance : Black. Cut surface: White, rose-color, blue, green. Adulteration : Earth, wood, portions of plants ; very moist. Loss in working : Quality I., 35 to 45 per cent.; II., 35 to 50 per cent.; III., 40 to 00 per cent. Quality I., very strong and beautiful ; II., partly soft ; III., frequently contains dead pieces. Borneo Djambes. Origin: Sumatra. Form: Balls and sheets. Appearances : Brown-red. Out surface : Greenish- red. Adulteration : Alumina, much water. Loss in working : 45 per cent, and over. But little in demand on account of the impurities. Borneo (Ben Koclen). Form: Thin sheets. Ap- pearance: Brown. Cut surface: Inside white. Adul- teration: Quite pure. Good quality. IV. AUSTRALIAN RUBBER. New Caledonia. Origin : New Caledonia. Form : Biscuits like Para rubber weighing 13 to 22 pounds ; also balls. Appearance : Pale and brown, sometimes a black tinge. Cut surface : White veined. Odor : Smoky. Adultera- tion : Very pure. Loss in working: 12 to 20 per cent. A very good quality, when not mixed with other varieties. Somewhat resinous. Has been but recently introduced in the European market. Statistics. As regards the statistics of the rubber RAW MATERIAL. 89 trade, there is the broad fact that the world's re- quirement in raw rubber is fast rising from 120 to 130 million pounds a year, in confirmation of which we give an estimate of the world's production and consumption of rubber, supported by such detailed figures as are available. Production. Brazil, Peru, etc. (Para). . . Brazil, Ceara, etc Brazil, Mangabeira .... Guiana Bolivia Rest of South America . . . Central America and Mexico Java, Borneo and Eastern Archipelago East and West Africa . . . . Madagascar and Mauritius . India and Burma Ceylon Australia . Cwt. 450,000 94,000 65,000 6,000 30,000 40,000 50,000 20,000 480,000 10,000 8,000 150 Cwt 1,250,150 Consumption. Cwt. America (United States and Canada) 400,000 United Kingdom and De- pendencies save Canada . 450,000 Continent of Europe 400,000 Cwt 1,250,000 The principal market for crude rubber in Europe is Liverpool, which of all kinds of rubber I In Imported, Tons. Sold, Tons. Remp.ined in stock, Tons. In Imported, Tons. Sold, Tons. Remained in stock, Tons. 1887 7330 5890 1440 1893 11330 9830 1500 1888 7900 6485 1415 1894 11560 16285 1275 1889 8750 7760 990 1895 13720 j 12640 1080 1890 9900 8610 1290 1896 17300 15640 1660 1891 10680 9480 1200 1897 15365 14285 1086 1892 10400 8950 1450 1 London, Hamburg, Rotterdam, Antwerp, Bor- deaux and Marseilles also import rubber. 90 INDIA RUBBER, GUTTA PERCHA, BALATA. The importance of the London market compared with that of Liverpool is shown in the annexed table : In Imported, Tons. Sold, Tons. Remained in stock. Tons. 1 In Imported, Tons. Sold, Tons. Remained in s-tock, '1 ons. 1887 2400 1385 1015 1893 1720 1280 440 18S8 2280 1313 977 1894 1935 1485 450 1889 1660 1050 610 1895 1720 1260 460 1890 1893 1247 646 1896 1579 1235 1137 1891 1900 1310 590 1897 460 344 320 1892 1740 1255 485 || The principal European countries together with the United States imported rubber in 1896-7 to the following approximate amount and value : COUNTRIES. Years. Quantity. Tons. Value. . Great Britain 1896 21 558 4 991 ] 99 1896 5 177 1,111 256 Germany 1897 8 436 2 320 150 Belgium 1897 2 ^36 545 835 Holland 1897 1 672 141 667 Austria-Hungary . . . United States 1897 1897 2,109 18*821 811,415 4 514 587 60,009 14,436,032 RAW MATERIAL. 91 Prices of India Rubber. (From S. Figgis & Co.'s Fortnightly Price Current, June 15, 1899.) s. d. s. d. India rubber ...... Red hard clean ball ......... 3 2 to 3 6 f White softish ball ....... . . . 2 8 to 3 East African Ports, Zan- [ Unripe root ............ 1 2 to 2 1 zibar and Mozambique - Liver and Lamu ball ........ 2 8 to 3 Coast ausage ordinary to fine ...... 3 to 3 L Sausage without sticks ....... 3 3 to 3 6 India rubber, Assam . . J Good to fine ............ 2 8 to 3 3 Common foul and middling . . . . 1 10 to 2 5 Rangoon ....... Fair to good clean ....... 2 11 to 3 1 Madagascar Tamatave, f Good to fine pinky and white ... 3 2 to 3 4% Majunga and Nossibe. ( Fair to good black ......... 1 8 to 2 (5 India rubber, Borneo . . J Fair to fine nigger ball ....... 1 5 to 2 7 < Fair to fine clean .......... 1 9 to 2 5 f Mixed, part dead ....... 1 1 to 1 6% Java, Singapore and j Good to fine red selected ..... 2 8 to 3 1 Penang ........ j Mixed, part soft ......... 1 7 to 1 10% [Pickings, part common ...... . 9 to 1 3 CHAPTER II. MECHANICAL TREATMENT OF CRUDE RUBBER. RUBBER in the crude state finds but little appli- cation, and besides the pieces used for erasing pencil marks, which are simply cut with a knife from Para biscuits, it is occasionally employed for billiard cushions, and in the form of square non-vulcanized threads. All other articles serving for thousands of diverse purposes, require more or less manipu- lation. In the industrial working of rubber, the first matter to be attended to is the removal of the various impurities present in the crude material. These, as previously mentioned, are in some cases natural products, which have originated with the rubber, while in other cases they owe their presence to careless collection or to adulteration. The ad- mixtures may range from fragments of bark or wood to stones or large lumps of clay, such as are sometimes introduced into niggerhead rubber, hay or a similar substance being also placed inside to make the mass about equal in specific gravity to the genuine article. Alum and sulphuric acid are often employed to effect the coagulation of the rnilky juice, and traces of them remaining in the rubber appear, in some instances, to work mischief. (92) TREATMENT OF CRUDE RUBBER. 93 The operation of purifying the crude rubber con- sists in softening and superficial washing, cutting up, rolling or actual washing, and drying. In manipulating the crude material it is advis- able to use only rubber of one and the same variety at one time, as different kinds demanded different treatment. Generally speaking, American rubber requires less manipulation than the East Indian or African article. Hence if the two kinds mixed in one lot were to be worked, the first would be purified while the other would require still further treatment. Softening or superficial washing. The rubber as brought from the store-room is too solid and hard to be worked, and the ordinary temperature of our climate is not sufficient to impart to it the requisite softness. Hence it must be artificially softened, which is the most simple of all the manipulations. The rubber is placed in water heated by steam, in which it remains from 3 to 24 hours, according to requirement. Wooden vats or iron tanks are most suitable for the purpose. For certain varieties it is recommended to add caustic soda to water, but the use of acidulated water should be avoided. ( 'idting up. The lumps of the softened crude rubber are then cut into slices by means of a sharp knife, generally by hand, as thus any large stones or other foreign substances can be removed. However, cutting machines are frequently used, the older kinds resembling somewhat a straw cutter. Sharp knife blades were set obliquely on the spokes of a 94 INDIA RUBBER, GUTTA PERCHA, BALATA. wheel which revolved rapidly. The lumps of rubber to be cut up were pressed by a lever against the knives, which were kept wet with water. Although such a machine is of quite simple construction and works satisfactorily, it has the disadvantage of re- quiring frequent repairs. For instance, if the edge of the knife hits a pebble in the rubber, it becomes notched, and then tears rather than cuts, and hence the knives must be frequently ground.. To prevent constant interruptions of the work, the knives should be so arranged that they can be readily taken off, and replaced by newly ground knives. An improvement in cutting machines is shown in FIG. 1. Fig. 1. In consists of an iron drum, a, 24 to 28 inches in diameter and 8 inches wide, with a large number of obliquely set knives, b b, which project slightly above the periphery, and are arranged in rows, as seen in the illustration. The lump of rubber is pressed against the knives TREATMENT OF CRUDE RUBBER. 95 by a lever arrangement consisting of the lever d, upon which the workman stands, and a joint lever, c, with its fulcrum at k, and the upper blade-shaped end, g y presses the rubber against the knives. A counter weight, h, brings the lever back, the manipulation of which is facilitated by the handle i. The drum, which revolves with great velocity, tears the rubber into small chips. Previous softening of the rubber is not required in working with this machine. Rolling or washing. This is the most essential part of the operation of purifying rubber, its object being to remove the foreign substances enclosed in the mass. Fig. 2 shows a machine most generally used for the purpose. It consists of two massive cast iron rolls lying horizontally alongside each other, and revolving with unequal velocity towards the inside. The surfaces of the rolls are either corru- gated or smooth, but the position of the two rolls is always the same. In English and American facto- ries corrugated rolls are preferred, since the corru- gations facilitate purification by penetrating into the rubber and grinding up the foreign substances. As shown in the illustration, the rolls rest in a strong iron frame. The bearings of the back roll rest laterally against the frame, and those of the front roll against two screws. The revolution of the rolls, each by itself, is, as a rule, effected by means of cog-wheels from a principal axis under the floor, though there are also machines in which the revolution is directly transmitted from one roll to 96 INDIA RUBBER, GUTTA PERCHA, BALATA. the other. However, the rolls always revolve to- wards the inside. By means of the screws on the front side of the frame, the rolls can be set closer or further apart. Underneath the rolls is a sheet-iron reservoir covered with a perforated plate. Over the rolls, about 1 to 1 \ feet, exactly above their point of contact, is a perforated pipe, through which during FIG. 2. the work cold water is constantly discharged, which runs off through a pipe in the sheet-iron reservoir mentioned above. The rubber to be washed is fed by the hand in very small quantities, according to the size of the machine, between the revolving rolls, the cock on the water pipe being at the same time opened. The rubber is caught by the rolls, crushed, torn and pulled apart, while the water penetrates TREATMENT OF CRUDE RUBBER. 97 into all the interspaces, washing away the particles of bark, fibres and earthy constituents, and remov- ing also all other crushed foreign substances. After repeatedly passing through the rolls, the product obtained is a long, blotting-paper like sheet with a wrinkled surface, which shows numerous small elevations separated from each other by small cavi- ties, and which gives a characteristic appearance to rubber in this state. Each machine is attended by one workman. The occupation is not without clanger, since by the slightest inattention the fingers may get between the rolls, and if the machine is not instantly stopped, the hand and arm will be drawn in. Hence every machine should be provided with a promptly acting disengaging gear. Such an arrangement will be described later on in speaking of masticating rolls. The size of the machines varies very much. However, as a rule, the rolls are 2 to 2J feet long, with a diameter of 1 J to 1 J feet, and the velocity is 8 to 12 revolutions per minute for one roll, and 3 to 4 for the other. Some factories use hollow rolls so arranged that they can occasionally be filled with steam, and in this case the machine, as "will be explained later on, serves for two operations. For large factories this arrangement, however, is not suitable. All varieties of- rubber cannot be Avashed with the same facility. Para rubber, containing the least impurities, is washed most quickly. The so-called fat or pitchy varieties yield the foreign substances 7 98 INDIA RUBBER, GUTTA PERCHA, BALATA. with difficulty, and frequently the impurities are so firmly fixed in the mass that they cannot be re- moved. Naturally very dry varieties of rubber can- not always be rolled into sheets or leaves, as they do not hold together, and in many cases the rubber comes in small pieces from the machine. If wash- ing is thoroughly done, the sheet contains no foreign substances, except water, which is removed by Drying, For tins purpose the rubber is suspended over iron wires or wooden poles either in lofts where it is exposed to the air, or "in drying chambers which can be heated to 122 to 140 F. This operation requires no special attention, but it may be said that fat or pitchy varieties require a low temperature for drying, since by drying at a high temperature their natural defects would become still more prominent. The sheets would tear, fall upon the floor and stick together in balls from which the water would evaporate very slowly and with great difficulty. Not very adhesive varieties of rubber which come in small pieces from the washing rolls are dried upon frames. For drying it is of great importance whether the room is more or less light, or more or less exposed to the air. A good draught facilitates drying extraordinarily, and in summer the operation is finished in a few days. More time is, of course, required in winter, and steam heat, carefully ap- plied, is then of great use. The injurious effect of strong light upon rubber has previously been re- ferred to, and hence the darker the drying room, the better. TREATMENT OF CRUDE RUBBER. 99 When dry the rubber is taken from the wires or frames, folded like cloth or rolled together in pack- ages. It is then brought into a special store room where it is protected from light and moisture and kept until required for further working. By washing and drying the rubber has lost a portion of its weight, the difference between the gross weight of the crude material and the net weight of the purified dried article constituting the loss in washing, The annexed table shows the loss with some varieties, though it is difficult to give definite figures : Para 10 to 16 per cent. Sernamby . . . . 15 " 35 " Mozambique (spindles) .. . 10 " 25 " (rose color, balls) 15 " 25 Columbia . . . . 10 " 25 " Peru (sheets) . . . 30 " 40 Guatemala . . . . 20 " 40 Assam . . . . . 10 " 30 " Java 20 " 35 " Borneo . . . . 10 " 45 " Guayaquil . . . 30 " 50 Senegal-Soudan . . .20 " 35 " It frequently happens that two shipments of rubber which are sold as the same variety vary very much as regards loss in washing, the difference amounting sometimes to as much as 25 per cent. Further working of the washed crude rubber. For the purpose of further manipulation, the washed 100 INDIA RUBBER, GUTTA PERCHA, BALATA. sheets when dry have again to pass through between rolls, this time, however, without the use of water. The rolls are hollow and heated by steam. Accord- ing to the purpose intended, they act either exclu- sively as a masticating machine, or at the same time as a masticating and mixing machine, their construction being, however, the same in either case. The machine consists of two rolls each about 2 to 3 feet long and 16 to 20 inches in diameter, which revolve one towards the other. As a rule they are placed one alongside the other, the arrangement of one above the other being the exception and seldom used at the present time. In all other respects they closely resemble the washing- rolls. The accompanying illustration, Fig. 3, a, b and c, shows mixing rolls from the front, side and above. It also shows the disengaging gear men- tioned on page 97. The latter has the advantage that the workman can engage it with one hand by pulling a rope, even if the other hand should have been drawn in between the rolls. Its con- struction and mode of operation are as follows : The rope F is carried tight over the pair of rolls from one standard of the frame to the other, then over a pulley G to the latch /. The latter is pro- vided with a catch which acts on the lever with the counterweight K. If now the instant disengage- ment of the rolls becomes necessary, the workman pulls the rope F. By this pull the latch /is drawn upwards, whereby the counterweight K is released ; K falls down and the piece M, which is rigidly con- TKEATMENT OF CRUDE RUBBER. 101 nected with the lever, makes a turn upwards, slides along on the surface of the screws and disengages the clutch coupling, whereby the disengaging gear is pushed to the left side, and the rolls are brought immediately to a standstill. Reengaging is effected as follows : The lever which carries the counter- weight K is lifted by means of the rope fastened to Fig. 3. it, the latch is again engaged and the disengaged gear L pushed to the right. While up to this point the treatment of all vari- eties of crude rubber for further manipulation is the same, from this stage on it varies according to whether pure unmixed mass for the manufacture of fine cut sheets is to be prepared, or a mixed mass which for certain purposes must receive necessary 102 INDIA RUBBER, GUTTA PERCHA, BALATA. admixtures. In the first case the rolls, as pre- viously mentioned, serve exclusively as macerating rolls, and in the latter, simultaneously as macerat- ing and mixing rolls. Fine-cut sheets form an important article of com- merce, and for their manufacture only the best quality of Para rubber should be used. The sheets of rubber, without the addition of any foreign sub- stance, are worked in the macerating rolls until a homogenous mass free from air is obtained, which comes from the machine in the form of rolls. The latter are subjected to strong pressure in a hydraulic press, whereby larger and more homogeneous blocks are obtained, which are stored for several months at a varying temperature by which means their text- ure becomes closer and their quality is improved. Other methods are in use for obtaining blocks of rubber from the crude and washed materials, which consist in forcing it into moulds without masticat- ing, and consolidating it by placing the moulds, keyed or wedged together with their charge, in a heater at about 240 F. for a few hours. Washed Para yields good sound blocks in this way, but the rubber is deprived of more of its strength than if masticated, and is darker in color. The blocks are next cut up into sheets of different thicknesses. Square blocks are clamped to a plate, which can be^ raised to any height, according to the thickness of sheet required. This passes forward to an oscillating knife, which slices up the rubber. The knife can, be set in an opposite direction, so as. TREATMENT OF CRUDE RUBBER. 103 to make another cut as it passes back again, and so on. Cylindrical blocks are forced upon a stout .spindle, which rotates in front of a similar, though much longer knife. The thickness of sheet is reg- ulated by the feed-wheels, which are changed as required, and when the machine is once started, a block can be cut without further attention unless demanded by a defect in the machine itself, which occurs generally in the friction arrangement which works the feeding gear. The machines are worked at very high speeds, and a good supply of water is kept continually flowing over the knives. The sheets are generally hung up to dry and season, and are soaped, and laid carefully one on the other, or rolled up for storage. The cutting up must be done in a cool room, for if the rubber gets soft, it must be again placed in a cold place to harden. Soft spots or patches will lead to inequalities in the thickness. The most usual commercial thicknesses in which these plates are manufactured are measured accord- ing to the following scale for the numbers : Nos. 1234567 4.15 3.26 2.58 2.35 1.85 1.66 1.40 millimeters. Nos. 8 9 10 11 12 13 14 1.14 0.96 0.83 0.62 0.54 0.46 0.41 millimeters. Nos. 15 16 17 18 0.37 0.33 0.20 0.18 millimeters. The manufacture of fine cut sheet was invented by Charles Macintosh, and was for a long time pro- tected by patent, which was owned by Charles 104 INDIA RUBBER, GUTTA PERCHA, BALATA. Macintosh and Co. They are, however, now manu- factured by several English firms and also in Fance and in Germany. They are frequently colored brown, red or green by the admixture of pigment, but green sheets have now almost entirely disappeared, black and brown being preferred, as they are better in quality. Up to within a few years adulteration of fine cut sheet was entirely unknown, but at present sheets are brought into commerce, which for the purpose of reducing the price, and frequently also with the object of defrauding, contain up to one- third of cheaper substitutes. In a similar manner as fine cut sheets, square threads may be cut from the pressed blocks. These threads were formerly frequently used in this crudo non-vulcanized state, but at present they are seldom employed, since non-vulcanized rubber becomes hard at 32 F., and soft and sticky at over 86 F. If, on the other hand, mixed mass is to be pre- pared from the washed crude rubber, the latter must first be softened by passing it through the heated macerating rolls to soften it for the reception of the admixtures. Mixing is, as a rule, effected in the same machine, which then serves as macerating and mixing rolls. A Frenchman has humorously designated the manufacture of rubber as " the art of mixing rubber with cheap substances without impairing too much its special properties." In order to be right, he might have added, " and to make its application more suitable for various pur- TREATMENT OP CRUDE RUBBER. 105 poses or to cheapen it." In fact in no other industry is there a material which is so receptive to these manipulations, and to which it is possible to impart so many varying qualities. The admix- tures consist of sulphur in sufficient quantity for vulcanization, and of other substances conditional either on the future use for which the material is intended or for the production of an exactly deter- mined degree of hardness, tenacity, as well as of color, or finally for the purpose of cheapening the product. The principal ingredients used are, lith- arge, zinc-white, chalk, heavy spar, metal, asbestos, ground hemp and a few other substances such as glass dust, fine sand, etc., which, however, are less frequently employed. Besides zinc-white, already mentioned, the following materials are used for coloring: Cinnabar, antimony pentasulphide, ferric oxicle, ochre, ivory black and lamp black. The receipts for these mixtures upon which besides the choice and use of the right variety of crude rubber, the production of the innumerable various qualities of vulcanized rubber depends, are jealously guarded in the various factories as trade secrets. For an exact repetition of a certain composition, an actual knowledge of the ingredients used is abso- lutely necessary, since a chemical analysis does not furnish sufficient guiding points for reasons which will be explained later on, and even practical experiments give only an approximately favorable result after long futile groping. The manipulation of kneading and mixing is very 106 INDIA RUBBER, GUTTA PERCHA, BALATA. simple, and is readily understood from the construc- tion of the machine and the nature of the material to be worked. The quantities of washed crude rubber, which, of course, must not be of the same kind, but of different varieties, which are required for the intended quality of the mass, and the sub- stances to be added, are carefully weighed and then introduced together in small portions between the rolls. The larger part of the material combines at once to a plastic mass, which either adheres by itself to the front roll and is carried along by it, or if such is not the case, is'taken up by the hand of the workman and lifted up. In this manner a loose mantle is rapidly formed upon the front roll, which glides through between the rolls as long as the machine is in operation. The material not taken up by the roll, or crumbs which become detached and fall upon the sheet underneath the rolls, are carefully gathered up and fed from above the rolls. The mass having several times passed through be- tween the rolls, the mantle is cut open crosswise with a short sharp knife, made into a roll, and the latter, head foremost, is again passed through between the rolls. This operation is repeated until uniform maceration and mixing have been effected. The mass in the form of a roll is then taken from the machine in the manner just described. In another form of machine, the rolls revolve in an iron box, the object of this being to prevent crumbs from falling down, and to save the attend- ance of a workman. Theoretically, this construe- TREATMENT OF CRUDP: RUBBER. 107 tion is correct, arul it will be referred to later under gutta percha, in the manipulation of which it is used, but in the rubber industry it has been found to be of no practical value. The rolls of rubber taken from the mixing ma- FIG. 4. chine are brought into a calender to be rolled into sheets. Fig. 4 represents a calender with four rolls. A, A!, A 2 , A 3 are four chilled iron rolls cast hollow, so as to admit steam or water. A and A 3 (Fig. 4) can be moved nearer to or further from A x , and A 108 INDIA RUBBER, (IUTTA PERCHA, BALATA. by screw-geariug worked by a wheel C and C 2 . The temperature of the rolls exerting great influence upon the uniformity of the sheets as well as upon the avoidance of stripes, so-called flowers, and especially of air bubbles, provision is made for the admission of cold water by a pipe on the axis of each roll, and in addition there is a pipe for the discharge of steam as well as of water. The sheets as they come from the rolls are caught by a cloth, and, to prevent sticking together, are rolled together with it upon a wooden spindle. CHAPTER III. VULCANIZATION. BEFORE describing this operation -,\ brief reference to some of the characteristic peculiarities of crude non-vulcanized rubber may be of service. As has previously been mentioned, at a temperature of SO F. it commences to get soft, and at 122 F. becomes very adhesive. But, on the other hand, at a tem- perature of 50 F. it becomes hard and stiff, and at 32 F. thin plates will break after being repeatedly bent backward and forward. By the action of atmospheric air and light, and especially in the presence of moisture and heat, crude rubber is oxid- ized and becomes a pitch-like, sticky mass. By the discovery of vulcanization these evils have been removed without impairing the valuable properties of rubber. Vulcanization is effected by combining rubber with sulphur with the assistance of heat. The celebrated French chemist Anselme Payen has made very interesting experiments in this direc- tion, and ascertained that w-hen a disk of crude rubber is submerged in a bath of melted sulphur, it swells up at 248 F., and absorbs a certain quantity of sulphur. In the course of a quarter of an hour the rubber shows no essential change, it being always sticky when touched. By continuing, how- (109) 110 INDIA RUBBER, GUTTA PRRCHA, BALATA. ever, the experiment 30 to 40 minutes and raising the temperature- to 206 to 284 F., the rubber acquires a yellowish color, it is no longer sticky, its elasticity is considerably increased, and it is no longer changed by the influence of cold. The same effect is produced when rubber previously mixed with flowers of sulphur is exposed for the same length of time to a temperature of 266 to 284 F., and also at every degree of heat between the melting point of sulphur and 320 F., the effect being the quicker the higher the temperature is. In this experiment are included all the distinc- tive features of the vulcanizing process. However, vulcanization can be effected not only by pure sulphur, but also by means of different sulphides, with chloride of sulphur, and several other sub- stances, such as iodine, bromine, etc. For industrial purposes, however, only pure sulphur is employed, and for special purposes the so-called cold vulcaniza- tion with carbon disulphide and chloride of sulphur. Cold vulcanization. According to this process, which was invented in 1846 by Parkes, of Birming- ham, the rubber is suspended for a shorter or longer time 1J to 3 minutes, according to thickness of the articles in a cold mixture of 100 parts of car- bon disulphide and 2J parts of dichloride of sul- phur. When taken from the bath the articles are quickly dried in a current of air of 77 F., or, in order to prevent the dichloride of sulphur from acting for too long a time, they are first immersed in lukewarm water and then dried. In place of VULCANIZATION. Ill carbon disulphide, carefully refined petroleum may be used. This process of vulcanizing is extensively used for surface-curing, such as single textures for gar- ments and sundry small articles manufactured from masticated sheet rubber, such as tobacco pouches, tubing, rings, etc. For thinner articles it has been recommended to use": Dichloride of sulphur 1 part by weight, carbon disulphide 30 to 40 parts, and to suspend the articles in the bath for 60 to 80 seconds. For thicker articles the following bath is recom- mended : Dichloride of sulphur 1 part by weight, carbon disulphide GO to 80 parts. Allo\v the articles to remain in the bath for 3, 4, to 5 minutes. Articles of extra thickness must be repeatedly plunged into the fluid until vulcanization is com- plete, when they are washed and dried. It is, however, more suitable in all cases to work with a reduced solution of dichloride of sulphur, as it is then possible to stop vulcanization at any moment. If the articles are allowed to remain too long in the solution, over-vulcanization may take place, that is, the surface .of the articles becomes hard and brittle. Small articles, especially such as have sharp out- lines produced by stamping, can be perfectly vul- canized by this method and their outlines preserved, which they would lose by any other process. Articles of special beauty should be thoroughly washed when taken from the bath, and then im- mersed for 50 to 70 minutes in boiling caustic soda 112 INDIA RUBBER, GUTTA PERCITA, BALATA. solution of moderate strength. The caustic soda dissolves the free sulphur and the surface of the article will present a uniformly gray color. It is immaterial whether solutions of dichloride of sulphur in carbon disulphide, or solutions pre- pared with the aid of anhydrous petroleum are used. For the sake of completeness the preparation of dichloride of sulphur and of anhydrous petroleum will here be given. Preparation of dichloi'i'dc. of .s///y> /////. Dichloride of sulphur is very easily prepared by passing dry chlorine over dry powdered sulphur. The sulphur should be dried immediately before the operation, and then placed in a tubulated retort provided with a receiver thoroughly cooled. The chlorine passes through a pipe fitted in the tubulure. Perfectly dry chlorine is obtained by passing it through a pipe filled with pumice stone saturated with sul- phuric acid. For the success of the operation it is absolutely necessary that both materials should be perfectly dry, since dichloride of sulphur decom- poses on coming in contact with water. The ac- tion of the two bodies upon each other commences as soon as the retort containing the sulphur is heated. A reddish-yellow fluid, consisting of a solu- tion of free sulphur with dichloride of sulphur col- lects in the receiver. To free the dichloride from the free sulphur the liquid is distilled until it boils at exactly 260 F. Distillation may, however, be omitted if the presence of free sulphur does not exert a disturbing influence upon the vulcanizing process. VULCANIZATION. 113 The apparatus shown in Fig. 5, is well adapted for the preparation of dichloride of sulphur. The chlorine passes from the developing vessel through the pipe a into the glass cylinder G. The latter is filled with glass balls moistened with sulphuric acid, and entirely dry chlorine passes into the earthenware vessel V, which is provided with an earthenware lid, D. The lid is provided with a neck E, which serves for the introduction of the sulphur. The FIG. 5. vessel V stands in a sheet-iron vessel filled with paraffin oil P, and is heated so that the sulphur S is heated slightly above its fusing point. The vapors of dichloride of sulphur escaping through C, are condensed in the glass receiver K. Dichloride of sulphur is a mobile, reddish yellow liquid, having a peculiar, penetrating, disagreeable odor, and fuming strongly in the air. Specific gravity = 1.680. It boils at 276.8 F. Brought in contact with moisture, it decomposes, forming 8 114 INDIA RUBBER, GTJTTA PERCHA, BALATA. hydrochloric and sulphurous acids, and causing a deposit of sulphur upon the neck of the bottle. As dichloride of sulphur severely attacks the mucous membranes of the nose and mouth, as well as the eyes, and produces a convulsive cough and difficulty of breathing, followed, if the air impreg- nated with its poisonous vapors is inhaled for any length of time, by lung and throat diseases, the greatest precaution should be observed to protect the workmen from its evil effects. It should be kept in bottles with ground-glass stoppers. Preparation of anhydrous petroleum. For this pur- pose bring the petroleum into a tank lined with lead and provided w r ith a stirring apparatus. Mix it with the tenth part of its weight of sulphuric acid, and after stirring the mixture for several hours, allow it to rest. The supernatant petroleum is then brought into a still, and to every 100 parts of it add J part of burned lime, finely powdered, to fix the last traces of acid. The petroleum is then distilled off. To prevent the petroleum thus rectified from absorbing moisture from the atmosphere, it should be kept in glass bottles securely stoppered, the bal- loons used for storing hydrochloric acid being very suitable for the purpose. Warm vulcanization. According to this method, invented by Hancock, the articles to be vulcanized are brought into a bath of melted sulphur heated to from 284 to 302 F., and allowed to remain in it until they are uniformly permeated and have ab- sorbed about 10 to 15 per cent, of sulphur. How- VULCANIZATION. 115 ever, before the articles are immersed in the bath, it is advisable to spread them out in a heated room for 24 to 36 hours, so that the seams cemented to- gether with benzine or rubber solution may become thoroughly dry, as otherwise they may burst open. After being taken from the sulphur bath, a solid crust of sulphur is formed, on cooling, upon the outer surface of the articles, which has to be scraped off or rubbed off upon grooved boards. The articles are then placed in a room heated to from 86 to 104 F. Notwithstanding the rubbing or scraping off of the outer crust of sulphur, the articles vulcan- ized according to this method contain still an excess of sulphur, which on rubbing or pulling the article, deposits a fine gray powder on the surface. This may be readily remedied by washing in weak soda solution. This method yields good results with articles made of fine cut sheets. When carefully carried out, it is preferable to cold vulcanization. Gerard's process. Ge'rard has recommended the use of concentrated solution of liver of sulphur (pentasulphide of potassium) for vulcanizing. The solution is obtained by fusing potassium carbonate together with sulphur. By using a smaller quantity of sulphur, trisulphide of potassium is obtained, Avith more sulphur than pentasulphide of potassium. For preparing the last-named combination, the fol- lowing quantities are used : Carbonate of potassium . 276.8 parts Powdered sulphur. . . 256.0 parts 116 INDIA RUBBER, GUTTA PERCH A, BALATA. However, the figures given above represent pure carbonate of potassium, i. e., 100 per cent, potash, and as the commercial article is never entirely pure, a smaller quantity of sulphur corresponding to the percentage of potash in the carbonate must be used. The substances are first reduced to a fine powder, then quickly mixed together, as potash absorbs con- siderable moisture from the atmosphere, and fused in a crucible in quantities of from 45 to 55 Ibs. The crucible must be comparatively large, as the mass, in consequence of the escape of carbonic acid, strongly effervesces during fusion. The mass is kept at the fusing point until effervescence ceases, and is then scooped with an iron ladle into shallow sheet-iron moulds and allowed to cool. The con- gealed mass of pentasulphide of potassium, com- monly called liver of sulphur, on account of its brown color, should at once be brought into closely- stoppered glass vessels, as it decomposes when ex- posed to the air. For vulcanizing, a concentrated solution (25 B.) of pentalsulphide of potassium is used. The solu- tion is quickly brought to the boiling point in a porcelain vessel. The articles are then immersed in the fluid and allowed to remain until vulcaniza- tion is complete. This process has the advantage of being entirely innocuous, and at the same time inexpensive. How- ever, to become generally available it would seem to require further improvements, as experiments have VULCANIZATION. 117 shown that only thin pieces of rubber become thor- oughly vulcanized, thicker pieces not being uni- formly penetrated. According to another process the rubber is al- lowed to remain for 3 hours under a pressure of three atmospheres in a solution of pentasulphide of calcium of 25 B., heated to 284 F. When taken from the bath the rubber is washed in water and dried. This method yields excellent results, the rubber being thoroughly and uniformly vulcanized and after washing presents a smooth, soft surface, almost velvety to the touch. However, this method is also only suitable for articles of smaller dimen- sions. For the purpose of employing it for larger articles, Gerard recommends to mix the rubber with finely powdered earthy substances, calcium hydrates being most suitable. Carefully mix in the mixing rolls rubber 100 parts, sulphur 6, calcium hydrate G to 10, and for vulcanizing expose the articles, according to their thickness, for 1J to 3 hours in a closed vessel to a steam or water bath at 284 F. Mechanical combination of rubber with sulphur. This process, invented by Goodyear, is the most important and most generally used. It consists essentially in mechanically mixing at the ordinary temperature a certain quantity of rubber with a certain quantity of sulphur, and exposing the mix- ture under a certain pressure to a certain degree of heat. To the washed and dried rubber is added in the mixing rolls 7 to 10 per cent, flowers of sulphur. Of course for certain purposes the addition of sul- 118 INDIA RUBBER, GUTTA PERCHA, BALATA. phur may vary between 3 and 15 per cent. Care- ful and uniform mixing is absolutely necessary for the favorable progress of the operation, since tho mass must be thoroughly homogenous. The work is commenced by passing the rubber through between the masticating rolls so as to form it into a loose band ; the rolls used for this pur- pose should allow of being heated by steam. The spongy band thus obtained is again passed through between the rolls, and at the same time is sprinkled with sulphur. When the requisite quantity of sul- phur has been applied, it is systematically kneaded in, which is best accomplished by doubling the band together and passing it through between the rolls, repeating the operation until a mass is ob- tained which to the naked eye appears entirely homogeneous. This mass, however, represents only a mechanical compound of the two substances, a chemical combination not having been formed. It is elastic in the cold, of a brownish color, is but slightly elastic at a higher temperature, and all the sulphur kneaded in can be readily extracted by proper solvents. Freshly-cut surfaces stick together, and this property is made use of for shaping articles from the sulphurized mass which are then subjected to the actual vulcanizing process. Articles may also be made from vulcanized rubber by cementing together the pieces composing them, but the manu- facture presents difficulties. Vulcanizing operation. As previously mentioned, the chemical combination between rubber and sul- VULCANIZATION. 119 phur takes place only when the mixture of both bodies is heated to a certain temperature. Opinions vary as to the degree of heat required for accomplish- ing this chemical combination, or vulcanizing as the operation is called, the chief reason for this differ- ence in opinion being due to the fact that the differ- ent varieties of rubber do not behave in the same manner. All Asiatic varieties (from the East Indies, Java, Borneo), require less time for vulcanization than the finer qualities of American rubber. The time required for vulcanizing depends on the thick- ness of the article, as well as on the quality and origin of the crude rubber. Articles with smaller cross-sections are frequently vulcanized in an hour, while thicker articles, and those of larger dimen- sions, require two to three hours. Vulcanization is the most difficult and critical operation in the manufacture of rubber goods, since the consequence of a little too much or too little may be over-vulcanization or an insufficient process, and these evils are the more disagreeable since their effect, as a rule, is only noticed when the articles are in actual use. No definite rules can be given in regard to the proportion in which sulphur has to be added, the correct temperature and how long each article must remain in the heater or the press. This must be left to the in- telligence and experience of the manufacturer. If the mass to be vulcanized is exposed to too high a temperature, over-vulcanization or burning takes place, whereby the rubber loses its elasticity and 120 INDIA RUBBER, GUTTA PERCHA, BALATA. soon becomes brittle, especially upon the surfaces. If the temperature is too low vulcanization is incom- plete, and in this case the rubber yields readily to pressure or pull, without, however, rebounding to its original condition when the pressure or pull ceases. A temperature between 248 and 302 F. may be considered the limit in which vulcanization will progress in a correct manner. In some cases it may be permissible to go above this limit and raise the temperature to 338 F., but only for a very short time. Experiments have shown that for properly vul- canizing rubber it is necessary to heat it above the melting point of sulphur. Now, as sulphur fuses at 235.4 F., theoretically it would suffice to heat the mass to be vulcanized to somewhat above that tem- perature. While it is possible to vulcanize rubber at 239 F., this fact is of little or no value for prac- tical purposes, as at that temperature the operation requires more time than the manufacturer can afford. From what has been said, it will be seen that the temperature for vulcanizing depends chiefly on the conditions under which the manufacturer works. If he works American rubber, and has to vulcanize articles with thick walls, a higher temperature is required than for East Indian material, and articles with thin sides. It is, therefore, advisable not only to work one and the same variety of rubber at one time, but also to subject only articles varying but slightly in thickness to the vulcanizing process at one time. VULCANIZATION. 121 t Vulcanizing apparatus. (Generally speaking, brick chambers heated by hot air are now antiquated, and are only used here and there in special cases, for instance, in the manufacture of lacquered rubber shoes and a certain kind of water-proof stuff. The chambers are provided with air-tight doors, and the floor consists of closely-joined iron plates. Several of such chambers adjoin one another, and are heated by one fire. The flues are arranged in such a manner that the tire gases must frequently pass to and fro under the iron plates of the bottoms of the chambers and heat the air in them uniformly. The articles to be vulcanized are placed upon frames close to the ceilings of the chambers, and the fire is so regulated that the thermometers, which are placed behind glass plates fitted into the doors of the chambers, show as uniform a temperature as pos- sible 266 to 284 F. It may be mentioned here that with the use of this method, complete vulcani- zation is frequently effected only by adding to the articles to be vulcanized a certain quantity of litharge. The use of iron boilers with double walls between which steam is introduced to heat the interior space is based upon the same principle as brick chambers. Vulcanizing heaters and presses, with direct intro- duction of steam, are now in general use. The ordinary steam heater is similar to a steam boiler. The size of the heaters varies according to the condition and dimensions of the articles to be vulcanized, Their diameter varies from 3 feet 3 122 INDIA RUBBER, GUTTA PERCHA, BALATA. inches to 20 feet, and their length from 6^ to 10 feet, and up to 100 feet and more. The longest heaters are used for vulcanizing hose, because the latter must, as a rule, be vulcanized full length FIG. 6. FIG. 7. upon the metal cores upon which they have been made. In England the standard length of hose is 60 feet, in France 82 feet, and in Germany 98 feet and 5 inches and even 114 feet and 9 inches. These dimen- sions indicate the length re- quired for the hose heater. ? Fig. 6 shows a heater in lon- gitudinal section and Fig. 7 in cross section. The heater <> is 16 to 20 feet long and has a diameter of 4J to 6 J feet, and is constructed like an ordinary steam boiler. In front it is provided with a strong cast iron ring v v into which fits a similar ring u u of the cover. To make VULCANIZATION. 123 a perfectly tight joint a tarred hemp rope is laid in the groove of the ring and the lid is then tightened by means of screws. The lid is suspended to a small crane T, 'so that after opening the heater it can be turned to the side, and also be readily re- placed. For the convenient introduction and re- "moval of the articles the heater is furnished with two iron rails upon which run small carriages containing the articles to be vulcanized, and besides suitable frames for the reception of the articles may also be placed upon them. U is a steam pipe pro- vided with the cock V for the introduction of steam. The steam is uniformly distributed by pass- ing into a long pipe V, and from the latter through a number of small holes into the heater. X, is the safety-valve, I 7 , the cock for the discharge of the atmospheric air and condensed water. In the illustration are shown at Q Q a few iron cylin- ders filled with buffer rings, and at R R frames which serve for holding rubber sheets between iron plates. Sheets, belting, large valves, etc., are vulcanized in a press, such as shown in Fig. 8. It consists of two plates, the bottom plate c, which is stationary, and the upper plate d, which is movable. Both plates can be heated by steam, and their heating spaces are connected by the spiral spring d. Steam is introduced from a point on the side of the press not shown in the illustration. The plate d can be raised sufficiently by means of the screws e, and nuts, which are uniformly moved by a horizontal 124 INDIA RUBBER, GUTTA PERCH A, BALATA. FIG. 8. shaft by means of the pulley p t to allow of the sup- port which bears the sheet or belt to be vulcanized, and glides upon the table a, being brought between c and d. FIG. A press heated by petroleum is shown in Fig. 9. VULCANIZATION. 125 It is intended for smaller articles, such as rubber stamps, etc. Vulcanizing operation. Besides observing the right temperature during heating, the mechanical treat- ment of the articles is also of great importance. It is not practicable simply to place the articles to be vulcanized in the heater, since in the high tempera- ture to which they must be exposed they would soften to such an extent as to lose their shape. Hence most articles are brought into the heater or press in iron moulds, such being the case with pump valves, buf- fers, thick rings, bands, cushions for billiard tables, belts, door-mats, balloons, and many other articles. Hose, as a rule, is vulcanized upon metal cores, and the outside is firmly wrapped with strips of linen. The latter are later on removed, and to this is due the tissue-like design frequently seen upon hose and sheets. If entirely smooth surfaces are desired, paper is occasionally used. For many kinds of goods it is important that the metals forming the moulds should not be readily acted on by sulphur during the heating, as a por- tion of the sulphur would be abstracted and leave a stain of the metallic sulphide on the goods. Con- sequently sheets of packing vulcanized in the press are prevented from coming in contact with the metal by sheets of cloth or paper. Tin is the most convenient metal for resisting the action of sulphur. Zinc sulphide being white, indicates the suitability of zinc for coating moulds, etc. All new zinc sur- faces should be well cleaned before use. A good 126 INDIA RUBBER, GUTTA PP:RCHA, BALATA. plan is to dust them over with sulphur and talc, and heat them in the heater several times, or they give rise to very troublesome blistering. Boiling with caustic soda helps to prevent this, but it is not certain in its action. Brass moulds should be well tinned. Hard rubber or ebonite forms very con- venient moulds, well adapted where metallic sur- faces would be objectionable from staining, etc. Stains from tin moulds or tinned surfaces are re- moved by leaving the vulcanized articles in hydro- chloric acid for some time. To prevent the articles from sticking to the moulds, they are dusted over with talc powder. The talc powder is put in a linen bag, and the moulds as well as the articles dusted over with it. Small curved articles may be placed in tin boxes filled with talc powder, and thus subjected to heating. Thick sheets are prevented from warping during heating by placing them between iron p^tes. Thin sheets are dusted over with talc powder, and covered with a linen cloth. In this condition they are wound upon a drum and brought into tho heater. Pressed hose and cords are placed in closed or open boxes in talc and then vulcanized. To avoid loss of time, the articles to be vulcan- ized should be sorted before heating. The thin and thick should be treated separately, as the latter re- quire more time for vulcanizing than the former. Many manufacturers effect vulcanizing in two operations. In the first operation, the heater is for VULCANIZATION. 127 a short lime heated only to a temperature not ex- ceeding 284 F. Articles that were too soft to be taken from the moulds acquire by this operation sufficient solidity to be heated by themselves. It is evident that this plan is attended with a loss of time and heat, and that it is more advantageous to finish the work in one operation. For many articles where it is of special import- ance that the mass of which they are composed should consist of thoroughly and uniformly sulphur- i/.ed rubber, the operation of vulcanizing is some- what modified. The articles are shaped in the usual manner from pure rubber, heated so far as to deprive it of its elasticity, and -pressed in moulds. They are then coated with a saturated solution of sulphur in carbon disulphide, and, while still moist, dusted over with powdered sulphur, care being had that the coating of sulphur is uniformly spread over the entire surface. For articles requiring only light treatment, the following process is sufficient : After being made from pure rubber, immerse the articles in oil of turpentine, and allow them to remain until their surfaces have become somewhat sticky. Then dust them over with finely-powdered sulphur, avoiding an excess of it. The articles treated with saturated solution of sulphur in carbon disulphide, or simply dusted over with powdered sulphur, are vulcanized in the same manner as articles of sulphurized rubber. Thin articles, when prepared with sufficient care, become 128 INDIA RUBBER, GUTTA PERCHA, BALATA. in this manner thoroughly vulcanized, but thicker articles do not, the product not being uniform. A cross-section will show plainly that only the surface is vulcanized, the interior parts remaining unaltered. In the manufacture of the various red colored rubber articles, hose, combs, etc., vulcanization is effected by an addition of pcntasulphide of anti- mony. The preparations of pentasulphide of anti- mony for this purpose found in commerce differ, however, very much in their action in so far that in vulcanizing, one kind gives always the desired red coloration, while another, which is not appreciably distinguished from it by color or content of sulphur, frequently or always yields a faulty product which shows itself by the color turning, or stains upon the surface. The cause of this difference in behavior of the pentasulphide of antimony is not yet known. Turner fuses bismuth 5 pounds and lead 5 pounds, mixes them, compounds the mixture with half its weight of sulphur, pulverizes after cooling, and mixes 10 pounds of the compound with 30 pounds of rubber. The articles vulcanized with this mixture are said to stand a temperature of 392 F. CHAPTER IV. RUBBER COMPOUNDS. FOR the manufacture of articles which are to possess in a very high degree the property of elas- ticity combined with toughness the use of pure sul- phurized rubber, /. e., a mass which lias been pre- pared from pure rubber and sulphur according to one of the methods described, is absolutely neces- sary. In some cases, however, elasticity is not so much required as cheapness of production, for instance toys for children, little cups, saucers, tubs, etc. Such articles contain a very small proportion of rubber, but many admixtures. The substances used as admixtures depend on the properties the articles are to possess. If a light color and little weight is desired, either fine white pipe-clay, chalk, or magnesia is mixed with the mass to be vulcanized. For white masses of greater weight, oxide of zinc is used, or sulphate of lead which, being a waste product of chemical factories, can be procured at a comparatively small cost. Cinnabar, round lake, sesqui-oxide of iron (caput mortunm, colcothar) are generally added to produce a red color ; ultra-marine or smalt may be used for blue ; chrome yellow furnishes the yellow color ; a 9 ( 129 ) 130 INDIA RUBBER, GUTTA PERCHA, BALATA. mixture of chrome yellow and ultra-marine, green ; colcothar and ultra-marine, violet, etc. Uniform coloring can only be effected by care- fully kneading the coloring matter into the rubber compound. But it can also be uniformly colored by producing certain chemical combinations in the mass itself, and some receipts for that purpose, applicable to rubber as well as gutta percha, are here given. For black a fluid is used consisting of: Blue vitriol . . . . 1 Ib. Water 11 Ibs. Caustic ammonia . . . 1 Ib. Muriate of ammonia . . J Ib. The blue vitriol is dissolved in water together with the muriate of ammonia, and the caustic ammonia is then added. For green the following are used : Blue vitriol . . . . \ Ib. Muriate of ammonia . . 1 Ib. Burned lime . . . .2 Ibs. Water 11 Ibs. For violet : Blue vitriol . . . . J Ib. Sulphate of potassium . . 1 Ib. Phenicine . . . . J Ib. Water 11 Ibs. RUBBER COMPOUNDS. 131 The articles to be dyed are boiled in their respec- tive fluids from 15 to 30 minutes, but articles some- what thicker must be boiled for a longer time to make the coloring uniform. The dyed articles can then be vulcanized in the usual manner. Rubber compounds which require to be rough are mixed either with powdered pumice-stone or the finest drift sand. The Jast two are added to the mass at the time when the sulphur is kneaded in, or in case the process of vulcanizing with a fluid chloride of sulphur is used, they are added to the pure rubber. To insure a completely uniform com- bination of the added ingredients, as clay, magnesia, pumice-stone, etc., it is absolutely necessary that they should be powdered as fine as possible, care- fully washed, and then thoroughly dried, as the presence of moisture is very detrimental. White or black pitch is also added to the rubber mass for the purpose of manufacturing cheap pro- ducts ; although many manufacturers assert that the properties of the product are essentially im- proved by such additions. This assertion, however, is not true, and is probably only made for the pur- pose of hiding the real object of these admixtures, namely, the production of masses in a cheap man- ner. In the following some receipts are given for preparing rubber compounds. These receipts have been tried and found useful. 132 INDIA RUBBER, GUTTA PERCHA, BALATA. White rubber masses. Parts by weight. Rubber 100 Sulphur 10 to 20 Chalk 40 to GO Magnesia . . . 5 to 40 Oxide of zinc . . . . 20 to 30 If the composition is to be colored, the coloring agent takes the place of one of the other com- ponents, either of chalk, magnesia, or oxide of zinc. This compound stands vulcanizing at a high tem- perature and can be finished in one operation. Cheap Rubber masses with an addition of Resin. Parts by weight. Rubber . 100 200 200 Sulphur . . 25 25 50 White pitch, or . 15 18 25 Pine resin . . 12 6C 20 Masses prepared with an addition of pitch or resin cannot stand a high vulcanizing temperature. When heated from 284 to 302 F. they become so soft that the mass would collapse over the mould. Therefore in vulcanizing it should only be heated very little above the melting point of sulphur, 235.4 F. A temperature between 239 and 248 F. will be most suitable for the purpose. Thinner articles prepared from these masses are quite elastic, but thicker ones are less so. RUBBER COMPOUNDS. 133 The Franco- American Rubber Co. prepares metallized rubber by mixing rubber with pulverized metallic lead, zinc, or antimony, and vulcanizing in the usual manner. For the preparation of vulcanized rubber which does not swell up when brought in contact w 7 ith fat, Schwanitz, according to a patent granted to him in Germany, uses Para rubber 6 Ibs., whiting 6 Ibs., glycerine of 1.23 specific gravity 1 lb., litharge 3J ozs., and flowers of sulphur 7 ozs. The mass is worked between heated rolls and exposed in a gly- cerine bath to the action of steam of a tension of 2 or more atmospheres. To make rubber pervious to perspiration in the use for articles of clothing, Scharff mixes it before vulcanizing with 10 per cent, of wood cellulose, the sulphur being added at the same time. Gerner mixes rubber and gutta-percha with cam- phor, cowrie copal, mustard or hemp seed, freed from oil and ground. For the manufacture of hard rubber articles the camphor and copal are separately ground in rolls. Then as much flowers of sulphur as is required for the articles to be manufactured is added, for instance, 1 lb. of sulphur, with J lb. of camphor and f lb. of copal. Before adding the rubber the mixture is finely ground and forced through a fine sieve. In working the materials are moistened with naphtha, gasoline or benzine. The quantities of camphor and copal to be used in the various mixtures for hard and soft rubber products depend on the kind and 134 INDIA RUBBER, GUTTA PERCH A, BALATA. qualities of the .articles as well as on the purpose for which they are to be used. For special kinds of hard rubber are preferably used J Ib. of the cam- phor and copal mixture, while for other kinds J or J of this quantity suffices. For soft rubber mixtures the composition and treatment of the mixture are the same except that less sulphur is required. In vulcanizing, the temperature has to be gradu- ally raised with great care. The mass, however, requires heating a shorter time than ordinary hard rubber, four to five hours being sufficient according to the thickness of the articles. During the last two hours the temperature is to be raised to 313 to 320 F. In vulcanizing soft rubber it is best to heat for the same length of time as in the ordinary process. The temperature should be raised at least to 280 F., and in many cases to 313 to 320 F. The larger the content of camphor and copal, the higher must be the temperature. Kamptulicon. The composition known by this name is especially well adapted for the manufacture of floor cloths subjected to hard usage, for coating articles, etc. Genuine kamptulicon consists of an intimate mixture of rubber and powdered cork, and is prepared as follows : Waste of cork, and old corks also, are cleansed by washing several times in water. The washed and well-dried mass is comminuted by grating upon a drum provided with small teeth like a rasp, and then ground into a fine powder. The rubber is cleansed in the usual manner, and RUBBER COMPOUNDS. 135 rolled into thin bands between closely-set rolls. The bands are strewed uniformly with the powdered cork, and then subjected to further treatment. This is done in the same manner as described for prepar- ing sulphurized rubber, that is, by rolling, kneading, and repeated rolling until an entirely homogeneous mixture has been formed. Finally, sheets 0.0787 to 0.1968 inches thick are formed, and these are covered either on one or both sides with a coat of good lin- seed-oil varnish or oil paint. Of course, with the assistance of oil paint, sheets with various patterns (carpet and parquet designs) can be produced. Powdered sulphur may also be incorporated with the rubber besides powdered cork, and the articles may be subjected to heating after they have been formed, and in this manner a vulcanized kamptuli- con is obtained. The principal advantages of kamptulicon are that with very little weight it combines great elasticity, and, for this reason, is well adapted for floor cover- ing in passage-ways, where the noise made by walk- ing is to be prevented as much as possible. Kamptulicon can be used as a block cushion under stamping presses to weaken the shock, but it should be inclosed in an iron ring to prevent splitting. It serves also to make wheels for polishing brass, steel, German silver, and other metals. This is done by covering a wooden disk with a piece of kamptulicon of the proper size. A uniform color can be made to permeate the entire mass, which can be worked into a kind of 136 INDIA RUBBER, GUTTA PERCHA, BALATA. mosaic in floor coverings. This condition is ob- tained by incorporating the coloring matter with the rubber. Colcothar, ultra-marine, lamp-black, etc., etc., are used for this purpose. The masses col- ored by any of the above substances are rolled out, and it is then a very easy matter to cut stars or other designs from them by means of a sharp knife or a suitable die, and to combine these into any desired pattern. As the matter is colored through and through, floor-cloths, or other articles manu- factured in this manner, retain their beauty as long as the articles themselves last. Rubber leather. Generally speaking this is identi- cal with kamptulicon, although it is sometimes manufactured in a different manner. While genu- ine kamptulicon is always composed of rubber and cork, rubber leather frequently contains, instead of cork, any kind of fibrous substance, such as hemp, flax, jute, etc. It is generally manufactured as follows: Rubber mostly in the form of small waste pieces, of which there will always be large quanti- ties in rubber factories, is either entirely dissolved by a solvent or at least allowed to swell up very much. The fibrous substance is then incorporated with the mass, and the latter is made homogeneous by long-continued rolling. The easiest way of incorporating the fibrous sub- stance is by stirring as much of it into the half-fluid mass of rubber and solvent refined petroleum being the best for this purpose as can conveniently be done. The mass is then placed upon a table, which RUBBER COMPOUNDS. 137 is quite thickly strewn with fibrous substance, and rolled into a cylinder. When in this manner a mass has finally been obtained, which possesses sufficient consistency to allow of it being worked between the rolls, the incorporation of fibrous sub- stance is continued there until a sufficient quantity of it has been kneaded -in to impart a suitable degree of solidity to the mass. It is advisable to repeatedly form the bands, which have been obtained by rolling, into lumps, and to pass these again through the rolls, as by these means the fibres are piled in different direc- tions (forming, so to say, a kind of felt), and by doing this the solidity of the substance will be con- siderably increased. As far as solidity and tenacity are concerned, rubber leather surpasses by far kamptulicon ; but the latter is softer and more elastic. Kamptulicon being rather expensive, it has been largely super- seded by linoleum, which is manufactured from a mixture of cork-meal, linseed oil and small addi- tions of resins. Ealenite or artificial whalebone is a material, as in- dicated by the name, intended to serve as a substitute for genuine whalebone. A mass to answer the in- tended purpose must possess considerable elasticity as well as solidity must, therefore, be a medium between soft and hard rubber. A mass answering the purpose very well is prepared according to the following formula : 138 INDIA RUBBER, GUTTA PERCHA, BALATA. Parts by Weight, Rubber 100 Ruby shellac .... 20 Calcined magnesia ... 20 Sulphur . . . . 25 Pentasulpide of antimony . . 20 The foreign substances are incorporated with the rubber, the mass is pressed into moulds, generally plates or prismatic bars, and vulcanized at a moder- ate heat. The mass which is thus obtained may serve in all cases as a substitute for the genuine whalebone, and may also be used for bobbins, etc. On account of its light weight and indestructibility, balenite may be highly recommended for the manufacture of gunstocks, as also of elastic plates and splints for surgical purposes. Plastite. This substance resembles bard rubber, but differing from it in being non-elastic, although quite hard. As it can be brought into any shape desired, and is largely composed of inexpensive substances, it is especially adapted for the manu- facture of pressed ornaments, small frames, boxes, heels of shoes, etc.; in short, for all purposes for which wool, metal, horn, etc., are used. Coal-tar asphaltum is an important component of plastite. It forms .a deep black, shiny and hard mass, and is gained in the distillation of coal-tar, as residuum after all volatile substances have been distilled off. Besides coal-tar, asphaltum, sulphur, and magnesia, and sometimes pentasulphide of antimony form a part of plastite. RUBBER COMPOUNDS. 139 Magnesia can be very well replaced by other in- different substances, such as finely powdered and washed chalk, etc., but the use of magnesia, which is a very light substance, offers the advantage that the masses can be made of great volume, and at the same time of little weight. A plastite mass possessing very good properties may be prepared according to the following formula : Parts by Weight. Rubber .... 100 Sulphur . . . . 20 to 25 Magnesia . . . . 40 to 50 Pentasulphide of antimony . 40 to 50 Coal-tar asphaltum . . 50 to 60 The foreign substances are incorporated with the rubber in the usual manner. The separate articles are pressed in hot iron moulds, and are then heated. On account of its great hardness and solidity, plastite takes a high degree of smoothness and polish, and for this reason is well adapted for the manufacture of handles for umbrellas and canes, door-knobs, etc. GRINDING AND POLISHING COMPOSITIONS. Rub- ber possesses the specific property of holding foreign substances, once incorporated with it, very tena- ciously. If the incorporated substances are hard, the mass is suitable for grinding or sharpening ; if soft, the composition serves for polishing. The first category includes powdered pumice-stone, powdered glass, quartz, sand, emery. To the second class belong colcothar, graphite, talc. 140 INDIA RUBBER, GUTTA PERCHA, BALATA. Below several formulse are given, which have been highly recommended, especially for sharpen ing and polishing knives : I. Rubber Powdered emery Lampblack Rubber Graphite Lampblack Rubber Graphite Lampblack Rubber Zinc-white . Yellow ochre Rubber Sulphur Powdered emery . II. III. IV, V. Parts by weight. . 280 . 1120 Parts by weight. . 280 . 512 Parts by weight. . 280 . 488 Parts by weight. . 280 84 1120 Parts by weight. . 280 84 1120 RUBBER COMPOUNDS. 141 As will be seen, formula I. and V. contain emery, which, on account of its hardness, serves as a grind- ing agent. The addition of lampblack in the other compositions is not essential, as the only object of it is to give them a black color. Nos. II. and III., on account of the percentage of graphite they con- tain, must be considered as polishing compositions ; and No. IV. also possesses the same property. It has been endeavored to prepare compositions which shall answer for one or the other purpose ; but one suitable for grinding, and at the same time for polishing, can only be prepared by using a hard body in the form of an impalpable powder, equaling in fineness the very finest flour. Graphite and talc, which of course must be pow- dered as finely as possible and washed, are especially adapted for polishing compositions. The rubber is mixed with 150 to 200 per cent, of this powder, and the entire mass is vulcanized by adding 10 to 15 per cent, of the weight of rubber of sulphur to it, and subjecting it to the heating process. Grinding compositions may be prepared by using powdered glass, pumice-stone, flint, or emery. The masses containing powdered glass or pumice-stone, being the softest, may be used for grinding brass or bronze, and those containing powdered flint, for grinding steel. The masses containing emery may be even used for grinding precious stones, as emery is the hardest body next to the diamond. To change the hard bodies glass, flint, and emery into fine powder, it is necessary to make 142 INDIA RUBBER, GUTTA PERCH A, BALATA. them red hot, and to throw them while in this con- dition into cold water. They become very brittle in consequence of the quick cooling off, and can then be ground into fine powder without great difficulty. If the grinding composition is to be subjected to considerable wear, it is advisable to add to the rubber, besides the powder of the hard body, some sulphur, and to heat the mass sufficiently to change the rubber into hard rubber. It is merely a matter of choice what form is to be given to the grinding and polishing compositions. Revolving circular disks, against which a piece of vulcanized rubber is pressed, are very suitable for sharpening and polishing table knives. If a knife is placed between the disk and the piece of rubber it will appear polished or ground after a few revo- lutions of the disk. For manufacturing purposes, especially for metal workers, it is best to give to the grinding or polish- ing masses the form of ordinary grindstones, that is, that of circular disks. The quantity of powdered hard substances to be incorporated with the rubber, may be a very large one, especially if hard rubber is used, and may amount to as much as four times its weight. Piubber enamel. Hard rubber, on account of its elasticity and toughness, is well adapted for coating- articles of metal which are to be protected against rust. For the purpose of coating metal with a thin layer of hard rubber, it is brushed over with a solu- RUBBER COMPOUNDS. 143 tion of rubber in benzine or petroleum, and is then dusted with powdered sulphur. Both operations are repeated after the first coat has become dry. The articles coated in this manner are quickly heated to a temperature of from 320 to 338 F., when the well-known reciprocal action between sulphur and rubber takes place, and they will come out with a coat of hard rubber. Defective places in the coating can be repaired by repeating the brushing over with the rubber solution, dusting with sulphur and heating. If it is desired that the coat should show an entirely uniform black color, it is advisable to dust the article with a fine black pigment after it has been dusted with sulphur. Frankfort black can be especially recommended for this purpose, as it forms an entirely dry powder which can be readily and completely dusted away, which is not the case with the majority of black pigments, for instance, lamp- black, as more or less tarry matter always adheres to them. The following process may be recommended for preparing colored enamels of somewhat greater thickness. An entirely clear, but rather thick solu- tion of rubber is prepared. This is intimately mixed with about 12 per cent, of the weight of the rubber originally used of the finest powdered sul- phur and the coloring substance to be incorporated. The mass obtained in this manner should have a consistency equal to thick oil paint. Should it be too thick to allow of it being evenly applied with a 144 INDIA RUBBER, GUTTA PERCHA, BALATA. brush, it may be reduced with oil of turpentine, or, in case it is too thin, this may be remedied by an addition of coloring matter. If benzine or carbon disulphide has been used as a solvent, it will be very difficult, on account of the great volatility of these fluids, to evenly apply the mass with a brush. It is therefore best to allow the rubber to swell up in benzine or carbon disulphide, and effect complete solution with oil of turpentine or rectified petroleum. Bristle brushes are used to coat the articles with the composition, and it should be done in thin but frequently repeated applications. If a white basis mass is used marbled designs can be produced by using yellow, red, or blue. The beauty of the work will of course depend on the skill of the workman. When the entire coat is finished it is dried, which can be accelerated by exposing the article to a tem- perature not exceeding 212 F. In case the enamel shows defective places it is repaired and finally heated at a temperature of 320 F. The rubber enamel manufactured in this manner adheres very tightly to metal, and will take a very high degree of polish. As it will stand a temperature of over 392 F., it can be advantageously used for enamel- ing the exteriors of self-feeding stoves, etc. Deodorizing vulcanized rubber. All articles manu- factured from vulcanized rubber possess a disagree- able odor, perceptible even after the articles have been in use for months. As this odor is very repugnant to some persons, who will not use rubber KUBBER COMPOUNDS. 145 articles simply for this reason, it becomes a matter of importance to remove this objection, especially with articles intended for personal use pocket books, cigar cases, etc. Vulcanized rubber may be deodorized in various ways : The articles are either exposed to a constant high temperature, or are treated with animal char- coal. While heating will remove the odor, to get entirely rid of it, it must be continued for many days, and this method is, therefore, not available in practice. On the other hand, animal charcoal pos- sesses in a high degree the property of absorbing odor. For the purpose of deodorizing rubber it should be used in the form of powder. A large number of articles may be deodorized at one time by treating them as follows : Cover the bottom of a sheet-iron box about } inch deep with powdered animal charcoal, upon which, place the articles. Fill in the spaces between them with animal charcoal and cover with a layer about f inch deep. Upon this another layer of articles is laid, and so on, until the box is filled, when it is placed in a room having a temperature of from 140 to 176 F., and left there from 3 to 8 hours, according to the size of the box. During this time the animal charcoal absorbs the odor, and the articles become entirely deodor- ized. But they must be stored in a special room, as they would again absorb the odor if stored with articles not deodorized. In the course of time, the animal charcoal loses its deodorizing ability and 10 146 INDIA RUBBER, GUTTA PERCH A, BALATA. must be replaced by fresh material, but it can be regenerated by calcining. This is done by placing it in a sheet-iron cylinder about 20 inches long, and closed on both ends by tight-fitting covers. The upper lid should have a hole the thickness of a straw to allow the gases to escape. The animal charcoal, after it has been thoroughly calcined, must be allowed to cool off before the cylinders are opened, as it would burst into flame and be con- sumed v if exposed to the air while hot. Desulphurized vulcanized rubber. As previously mentioned, only a small portion of the sulphur about 1 to 2 per cent. combines chemically with the rubber, the greater portion being only mechan- ically mixed with it. This sulphur, however, be- comes effective in time and causes the articles to become brittle and hard after long storage. This defect will show itself especially in rubber hose, which becomes so hard that it will break when an attempt is made to bend it. To prevent this evil the excess of free sulphur is removed by boiling the vulcanized rubber in caustic soda or caustic potash lye, whereby the free sulphur is gradually dissolved, while the chemical combination of sul- phur and rubber is not attacked. The time required for boiling depends on the strength of the lye used and on the quantity of free sulphur present. The best plan is to take occasion- ally a piece of the rubber from the boiler and by it test the progress of desulphurization. The color of desulphurized rubber closely resembles that of the RUBBER COMPOUNDS. 147 ordinary product. Therefore, as long as the piece shows the -characteristic grayish coloring of ordinary vulcanized rubber, the mass is not properly desul- phurized, and the boiling must be continued. Vulcanized rubber, from which the excess of free sulphur has been properly removed, only requires washing and drying after it has been taken from the lye, and is then a product which may be called the most perfect of all rubber preparations, as it remains not only entirely soft and elastic in all temperatures, but does not become hard even if stored for a long time, and has no odor whatever. It is well adapted for manufacturing articles for surgical or scientific purposes or to be used in the nursery or sick-room nursing nipples, rubber cloth to protect bedding, etc. It is also an excellent material for gas-tubing, as it combines great pliability with perfect imper- meability to gas. CHAPTER V. HARD RUBBER. IT has previously been mentioned that when vul- canized rubber contains too much sulphur, and is exposed to a higher 'temperature for a longer time than necessary for vulcanizing, it becomes hard and horn-like. Hancock observed this at an early date, and makes mention of it in his first patent-specifica- tion. . Goodyear continued the experiments, and some years later patented a method for manufactur- ing, from rubber and gutta-percha, with the addition of other substances, articles which were formerly made of wood, leather, metal, etc., and which at the same time were lighter and cheaper. Generally speaking, the preparation of hard rubber is based upon the same principles as that of vulcanized rubber. The crude rubber is softened, washed, dried, macerated, mixed, according to cir- cumstances, with other specially suitable varieties of crude rubber, and compounded with sulphur and other ingredients. The addition of sulphur may amount to as much as 50 per cent. In place of pure sulphur, other sulphur combinations, such as sul- phide of antimony or sulphide of lead, can be used. Goodyear has recommended a zinc compound, which is prepared as follows : Solution of zinc sulphate or (148) HARD RUBBER . 149 acetate is precipitated with solution of liver of sul- phur, either direct or after the latter has been de- colorized by the introduction of sulphurous acid. The precipitate thus obtained is thoroughly washed with water and used after drying. Besides sulphur, other substances such as zinc- white, whiting, magnesia, etc., may be added to the mass while being treated in the rolls, the proportion of such additions depending on the demands made on the finished material as regards elasticity, flexi- bility or hardness, as well as color. The prepara- tory operations require still greater care and atten- tion than in the preparation of soft rubber, as a very small quantity of water and very small air bubbles enclosed in the mass may make it porous or even entirely ruin it in consequence of the high temperature to which the material is later on exposed. Hard rubber is used in the manufacture of many articles, such as combs, spindles, shuttles for spin- ning and weaving, cigar and match cases, valves, pumps for corrosive fluids, surgical instruments, etc. The rubber, sulphur and other ingredients are combined between mixing rolls, the operation being continued until a thoroughly homogeneous mass has been formed, which has the consistency of dough, and can be shaped into all possible forms. The prepared crude mass is rolled into plates of various thicknesses, and the separate articles made from them by pressing in moulds. Small boxes, spectacle cases, etc., are moulded over solid cores. 150 INDIA RUBBER, GUTTA PERCHA, BALATA. Sometimes larger sheets are rolled out, vulcanized, and then worked like wood or horn, with a lathe, or saw and plane. To prevent, in filling the moulds with the pro- pared mass, air bubbles from remaining between it and the mould, En gel, according to a German patent, first fills the mould with linseed oil, then presses the prepared rubber mass into the mould so that in vulcanizing, the small remaining portion of the oil is absorbed by the rubber. Vulcanizing hard rubber requires either one or two operations. If ordinary articles or simple sheets are to be treated, one operation suffices, but for more complicated shapes it is advisable to per- form the work in two operations. If vulcanizing is to be done at one operation, the articles are placed in the heater, and heated for several hours three to six at a temperature of 302 F. Manufacturers differ in their statements about the degree of heat, but these are of little value, as every practical man will soon find out for him- self. It is stated, for instance, that especially excel- lent properties are given to hard rubber by first heating it for two hours at 230 F., then quickly raising the temperature to 302 F., and keeping it there for several hours. By this process articles are obtained sufficiently vulcanized, as a temperature of 302 F. suffices to convert quite thick objects into hard rubber in the course of several hours, but it is difficult to under- stand the object or effect of Ji eating them for two/ HARD RUBBER. 151 hours at 230 F., as sulphur, as is well known, only fuses at 235.4 F., and it is scarcely worth while to talk about sulphur producing any effect before it is melted. By special experiments in this line it has been ascertained that, even after the mass had been heated for several hours at a tem- perature of 230 F., by far the greater part of the sulphur could be extracted from it in an unaltered state by a solvent, this being a sure proof that no chemical action had taken place. Hard rubber suffers considerable contraction in the course of vulcanizing, and the shrinkage of the articles allows of their removal from the moulds by a gentle tap. The shrinkage being uniform, owing to the even temperature, the articles do not warp. Articles of a not especially complicated shape may be vulcanized without the use of a mould. Flat articles may be treated without further prepar- ation by laying them upon iron plates, but if other articles are to be vulcanized without the use of moulds, it is advisable to dust them over with magnesia or powdered chalk, and to place them in sheet-iron boxes filled with fine sand in such a manner that the articles are completely covered by it on all sides. The sand prevents the articles from collapsing during the first period of heating, an event which it would be very difficult to avoid without it. By the above process skilled workmen can vul- canize and finish in one operation quite complicated articles, with a very small percentage of defective 152 INDIA RUBBER, GUTTA PERCHA, BALATA. products. However, to prevent any possible failure it is advisable to divide the vulcanizing process into several operations. In this case the first operation, at a temperature of about 293 F., lasts but one hour. The articles then acquire a considerable degree of solidity, and can be taken from the moulds to undergo inspection. The perfect pieces are immediately put back in the heater and finished without further manipulation, but those showing defective places, cracks, holes, etc., are repaired with a dough-like mass of rubber, and heated for another hour, when they are again inspected and repaired, if necessary, and heated for another hour this alternate inspection, repairing, and heating being continued until the articles can pass for finished goods. Hard -rubber, prepared from crude rubber and sulphur only, has a black color, and takes a very high degree of polish. Articles manufactured from this material, although black, can also be colored any desired shade. A distribution of the coloring substances through the entire mass has the advantage of considerably increasing its weight, but it also, to a great extent, injures its properties. To give hard rubber any desired color without altering its internal properties two methods, which may be designated as "dusting," and "plating," or "enameling," are made use of, both being well adapted for the purpose. Dusting is done as follows : After the article has been shaped from the prepared crude material, it is HARD RUB] thickly dusted over with a finely-powdered coloring- matter contained in a linen bag. The mould into which the article is to be pressed must first be uni- formly dusted over. After vulcanizing the article should show a uniform coloring. Any defect is re- paired by repeating the dusting over and reheating. Articles of an entirely uniform color can be ob- tained by plating or enameling as follows : A mass is prepared from crude rubber and sulphur in the usual manner by rolling, the coloring matter being at the same time incorporated with it. Rolling is continued until a uniformly-colored paste is ob- tained. The paste thus colored is rolled into a sheet about half as thick as the sheet to be enameled, and if only one side of the latter is to be treated, the two sheets are laid one upon the other and rolled out to the thickness acquired for the articles to be made. If the rubber is to be enameled on both sides, a plain sheet is placed between two colored ones. In this manner a different color may be provided on each side, and an enamel of any desired thickness applied. The thinner the enamel, the thicker, of course, the enclosed plain sheet must be. Frequently the smaller portion of articles called hard rubber consists of actual rubber, various indif- ferent substances, such as chalk, magnesia, zinc- white, etc., being added for the purpose of increas- ing the weight. If these admixtures are intended to impart a certain color to the rubber, care must be had not to use a coloring matter which may be 154 INDIA RUBBER, GUTIA PERCH A, BALATA. affected by sulphur, otherwise the coloring may turn out the reverse of what was intended. For this reason coloring substances containing lead,' such as white lead, chrome yellow, etc., must be avoided, since lead readily combines with sulphur, forming black sulphide of lead, and in this case black instead of white or yellowish masses would be obtained. What has been said about lead compounds, applies also to coloring substances containing copper. Lakes, prepared from organic substances and alumina, as well as zinc colors, may be used for coloring hard rubber without any further prepara- tion, except that the lakes must be perfectly dry before they are incorporated with the mass. If used moist, the water contained in them is, during the vulcanizing process, converted into steam and the bubbles thus formed cause the mass to bulge up and the surface to become rough, while the interior will not be compact but porous. The waste resulting in moulding tho articles is immediately kneaded together, passed through be- tween the rolls, and may then be used in the manu- facture of other articles. But the waste from hard rubber, i. e., after it has been vulcanized, can only be utilized for the preparation of lacquer, which will be referred to later on. The best plan is to shape the articles by pressing or stamping them from the mass, as there is much less waste than when preparing sheets from which the articles are to be manufactured. The hardness and elasticity of hard rubber prin- HARD RUBBER. 155 cipally depend on the quantity of sulphur which has been added to the crude material. Below a few receipts adapted for the purpose are given. Articles sufficiently elastic and pliable, so that they will not break,- even when sharply bent, can be made from the following composition : Parts. Rubber 86 to 88 Sulphur 14 to 12 This is especially well adapted for manufacturing combs and such thin articles as are to possess a high degree of elasticity and considerable solidity. By mixing together : Parts. Rubber 76 to 80 Sulphur 24 to 20 a mass is obtained which, in regard to elasticity, is nearly equal to the foregoing, but is somewhat more fragile. The larger part of the articles, as combs, etc., sold as hard rubber are made of a composition re- sembling the latter, but containing more sulphur and consequently are much cheaper. Ebermayer has examined hard rubber combs from various factories and found that their elasticity is conditional on the content of sulphur. Thus a mass with 11.95 per cent, sulphur could be readily bent but not broken, while a mass with 21.46 per cent, could be broken only with difficulty, and one containing 28.25 per cent, was extremely brittle and hard. 156 INDIA RUBBER, GUTTA PERCHA, BALATA. When great hardness and solidity, with but little elasticity are required, as in a material suitable for knife handles, rollers, buttons, tool handles, door knobs, lock plates, etc., the percentage of sulphur is increased and Parts. Rubber ..... 65 to 76 Sulphur . . . . .35 to 24 form the best compositions for such purposes. It is a remarkable fact that some resins, although quite brittle by themselves, impart a certain elastic- ity to hard rubber. Shellac is especially effective in this respect. It can be used either bleached or unbleached (the so-called ruby shellac). The latter is to be preferred for articles of a dark color, as it is far cheaper than the bleached article, and answers the purpose equally well. The shellac should be powdered as fine as pos- sible, and intimately mixed with the rubber by con- tinuous rolling. A piece of shellac large enough to be visible to the naked eye would be sufficient to spoil the appearance of the article. Hard rubber will bear the admixture of a large quantity of shel- lac, and in some cases an amount equal to that of the crude material may be used. A composition consisting of: Parts by weight. Rubber ' 88 Sulphur 12 Shellac 50 HARD RUBBER. 157 was formed into sticks having a cross section of 0.155 square inch, which could be bent to a consid- erable extent after they had been vulcanized, but were at the same time so elastic that the sticks always sprung back to their original straight form. The rubber was so hard that thin shavings could be cut from it only with a very sharp knife. In consequence of these properties this variety of hard rubber furnishes an excellent material for the man- ufacture of bobbins and shuttles, as these can be made so thin that their sides are scarcely thicker than thin paste-board. Hard rubber can be used with great advantage for making bowls for silver-plating baths, spatulas, rollers and other utensils used by photographers, also for stoppers and caps of bottles containing corrosive fluids. Newton prepares buttons, knife handles, etc., by mixing gutta percha, with or without rubber, with an equal weight of sulphur and exposing the mix- ture to a temperature of from 248 to 302 F. For every pound of gutta percha may be added J to f Ib. of a mixture of chalk, gypsum, shellac and resin. Johnson uses a mixture of sulphur 1 part, zinc oxide 9 parts, and rubber 9 parts for the manufac- ture of brushes, curry-combs, etc. Hard rubber is much used in the manufacture of black ornaments, such as brooches, earrings, brace- lets, chains, etc., which resemble jet and even onyx, when finely polished. But as the pieces come more or less dull and dead from the moulds the 158 INDIA RUBBER, GUTTA PERCH A, BALATA. require polishing, which is clone either upon the lathe or by means of cloth or felt wheels, and sometimes with the use of a fine polishing agent. Since this mode of polishing considerably increases the cost of the articles, it lias been endeavored to find a. process which renders polishing entirely superfluous or at least facilitates it. The use of glass moulds or lining the iron moulds with thin tin-foil has yielded good results in this direction. Many rubber articles require a combination be- tween hard and soft rubber, between soft and semi- hard, semi-hard and entirely hard, or between all three. Such problems are, for instance, presented in lining iron boilers intended for the reception of acids (montejus), in the fabrication of coatings for rolls, especially of larger dimensions, such as are used in the manufacture of paper and leather, and in finishing cotton goods, and in the manufacture of many other smaller articles. The correct and suitable solution of such problems requires besides close supervision of the workmen, very careful se- lection of the varieties of crude rubber and admix- tures to be used, as well as many years' experience in vulcanizing. The physical and chemical properties of hard rubber are entirely different from those of crude rubber. It is black, entirely without odor, horn- like, and not unlike hard wood or ivory. It is dielectric, but becomes electric by vigorous rub- bing. Cold water, light and atmospheric air, have no effect upon it. It does not oxidize. In boiling HARD RUBBER. 159 water, however, it becomes soft and flexible. To- wards solvents, which completely dissolve crude rubber and partly vulcanized soft rubber, it is en- tirely indifferent, and it resists acids to a high de- gree. Exposed for some time to dry temperatures of above 392 F., it does not become firat sticky like natural crude rubber, nor melt like soft vul- canized rubber, but commences to carbonize with- out having yielded an intermediate product. Preparation of artificial ivory. For many years chemists have endeavored to prepare a substance to serve as a substitute for ivory, which is every year becoming scarcer and dearer. Their attention was principally directed to compositions w r ith glue as a base, to which were added finely powdered white substances, and such bodies as would make the glue insoluble ; the salts of alumina and tannin being chiefly used for this purpose. It cannot be denied that the process of preparing such masses has been successful as far as their external appearance is concerned, it being scarcely possible to distinguish them from genuine ivory. But they lack one of the principal properties of the genuine article, namely that of combining great elasticity with solidity. It has been tried to utilize rubber for preparing a mass which would possess as nearly as possible all the properties of ivory, and these experiments have been so successful that substances are now obtained which can be employed for manufacturing a large number of articles formerly made of ivory. But 160 INDIA RUBBER, GUTTA PERCHA, BALATA. they cannot take the place of the genuine material where elasticity combined with great solidity is a requisite. Many attempts have been made to manufacture billiard balls from such composition, but they have never been very successful, the balls in a short time becoming full of cracks, and break- ing even when but gently struck. For the preparation of an elastic mass a certain percentage of pure rubber must be added, but the resulting product is not of a sufficiently light color. It may here be mentioned that many products are sold as artificial ivory which contain but a small quantity of rubber or gutttf-pcrcha, foreign substances, which impart weight, being the chief components. The same may be said of compo- sitions sold as hard rubber which contain less than 33 per cent, of rubber. Every imaginable kind of bleaching agent lias been tried and recommended for decolorizing and bleaching rubber, but no process has been entirely successful, and it may justly be said that with the means at present at our command it is impossible to obtain results entirely satisfactory. If rubber be treated with a bleaching agent which exerts any kind of effect upon it, it will acquire a lighter color a very light yellowish-brown but a chemical change will at the same time take place, and the mass bleached, for instance, with chlorine, cannot be called rubber any longer. Several methods have been published, by which it is claimed rubber can be bleached without suffer- HARD RUBBER. 161 ing a chemical change ; but on testing these methods, the result was always the same, namely, the bleached product did not possess the properties of rubber. Nearly all these methods amount to the same thing, namely, that the rubber is allowed to swell up very much complete solution not be- ing necessary and chlorine be introduced into the swelled-up substance. The most suitable solvents for the purpose are carbon disulphide, benzene and rectified petroleum, though chloroform and oil of turpentine have also been recommended. For treating rubber with chlorine a special appa- ratus is required. This consists of a wooden vat lined with lead. It should have a lid or cover lined with lead and capable of being secured air- tight. In the centre of the lid or cover is a revolv- ing shaft connected with a stirring apparatus made of leaden rods. The pipe conducting the chlorine reaches to the bottom of the vat, and a funnel pro- vided with a stop-cock is fitted into the cover to admit new fluid when required. A small pipe is fitted into the cover and passed into a tank of water adjoining the vat, for the escape of the chlorine. Fig. 10 shows the arrangement of the apparatus. The chlorine enters through C ; R is the stirring apparatus ; J is the funnel ; A the escape pipe for the chlorine ; H is a stop-cock in the bottom of the vat, covered inside with a leaden sieve. The rubber, cleansed and cut in small pieces, or, still better, in shreds, is placed in the vat, which is then closed, and the solvent poured in through the 11 162 INDIA RUBBER, GUTTA PERCHA, BALATA. funnel J. The stirring apparatus R is started and kept in motion until solution is complete. The chlorine is then introduced and allowed to flow until its escape is noticed from the pipe A. Alco- hol equal in volume to that of the solvent is intro- duced into the vat through the funnel J, which FIG. 10. causes the bleached rubber to be separated and pre- cipitated in a slimy condition. The solution is constantly stirred to permeate it with the alcohol. The stop-cock H is then slightly opened to allow the fluid to run off. The alcohol and original solvent are finally separated by distillation. The apparatus above described, though very effective, is somewhat obsolete, since for the prepa- ration of chemical products in general and espec- ially of chlorine, clay vessels are now made in HARD RUBBER. 163 numerous factories which are cheaper and just as effective as wooden vats lined with lead. As has been stated, rubber bleached in the manner above described is of a brownish-yellow color, and should be immediately worked, as it is quite soft when it comes from the bleaching appa- ratus, and can be easily compounded with ad- mixtures. According to an American process 2 Ibs. of rubber are dissolved in a suitable vessel in 4 Ibs. of chloroform. The solution is allowed to clear by settling, and ammonia is then introduced to satura- tion. When the rubber is completely bleached, which is ascertained by frequently examining a sample, the solution is washed with hot water in a vat provided with a stirring apparatus, to remove all traces of ammonia and chloroform. The sepa- rated rubber forms a spongy mass which is squeezed, pressed, dried and mixed with sufficient chloroform to form a thick dough. This dough is intimately compounded with enough phosphate of lime or carbonate of zinc to form a mass having the appearance of damp flour, which is pressed in hot moulds. The articles taken from the moulds may be further worked in the turning lathe. By adding suitable coloring matters with the phosphate of lime, imitations of coral, enamel, etc., can be prepared. The simplest method of bleaching rubber for pre- paring artificial ivory is to treat it in the usual manner, and to form thin bands from it by passing 164 INDIA RUBBER, GUTTA PERCHA, BALATA. it through the rolls. These are allowed to fall into a roomy vat, provided with a cover, and containing water saturated with chlorine. By using the rubber in the form of thin bands, the bleaching process goes on quite rapidly, and when complete, it is only necessary to wash the mass several times in hot water to free it from the adhering chlorine. It is advisable to add a small quantity of sodium hyposulphite (1 per cent, of the salt is sufficient) to the first washing water, as this salt has the effect of removing every trace of chlorine which may still be present. If any of the chlorine were to remain it would exert an injurious effect afterwards when the material has to be worked in machines constructed of metal. The best plan is to subject the bleached mass to further treatment immediately after it has been washed, as it is then very plastic. But if it is not desired, nor possible to use the mass at once, it is advisable to moisten it with some carbon disulphide or benzene and to let it remain for some time in a hermetically closed vessel. A small quantity of the solvent will cause the mass to swell up some- what, and it can then be worked with greater ease. The next operation for preparing artificial ivory is to incorporate several substances with the plastic mass. Either whiting, oxide of zinc or white lead is used for producing a white material. Arti- ficially prepared sulphate of baryta (the blanc or fix permanent white used as a coloring substance by the manufacturers of wall papers) is also a very HARD RUBBER. 165 suitable material for the purpose. Articles colored by pigments containing white lead, lose their white color in time and turn gray. The colored masses are worked in different ways, either direct or indirect. If the direct method is chosen, the artificial ivory is immediately pressed into hot moulds, but sharp impressions can only be obtained by using a very high pressure. Many elegant articles can be prepared in an inexpensive mamier by this method, provided it is not absolutely necessary that the substance should be entirely homogeneous. Knife handles, buttons, etc., may be prepared by direct pressing. For solid, but at the same time non-elastic articles, it is best to use the indirect method, that is to say, the mass is formed into cubes, and the articles are shaped from them by the lathe, etc. Therefore the preparation of artificial ivory must be regulated by the use intended. For instance, the material for billiard balls should undergo less pres- sure than that for making thin sheets. The greater part of the numerous receipts given for preparing artificial ivory, are of no special value, as its quality depends so much upon the rubber used, the duration of the chlorine treatment, etc. According to many of the receipts, masses are made resembling vulcanite, by using sulphur and gutta- percha in addition to rubber, and heating them to 302 to 320 F. Jacobsen gives an American receipt, according to which a mass for artificial ivory consists of the following substances : 166 INDIA RUBBER, GUTTA PERCHA, BALATA. Parts. Rubber 100 Sulphur ...... 45 Gutta-percha 10 The mass is heated to 314.6 F. While it has been considered of interest, for the sake of completeness, to give a description of the manufacture of artificial ivory from rubber, with the present high prices of the latter material the product is not remunerative, especially as at the best it is an imitation, which lias many defects. Besides, masses are now prepared from celluloid, which as regards their properties, resemble more closely ivory than the best rubber compositions, and are much cheaper. CHAPTER VI. MANUFACTURE OF ARTICLES FROM SOFT RUBBER. WITH the exception of waterproof stuffs, the man- ufacture of rubber articles depends upon plastic manipulation, the greater portion of the work being done by hand. Actual machinery is but little used, but, on the other hand, a great variety of rnoulds arid presses are employed. The best known articles in general use made from fine cut sheets are : Nipples and fittings for milk bottles, tobacco pouches, tubes for chemical laboratories, and the many articles for chirurgicai and technical purposes, for which no other rubber material is as suitable. The manufacture of these articles depends on hand work, and is very simple, because the cut surfaces of the sheets produced with a knife, die or scissors when pressed together adhere immediately, this being still more the case if a thin coat of benzine or of thin rubber solution be first applied to them by means of a small brush. Hence it is only necessary to cut out according to a pattern with scissors or a knife the several parts of the articles to be manufactured, or when large quantities are to be produced, for instance, nipples, to die them out and then put them together either by hand or over a mould. In order to make a (167) 168 INDIA RUBBER, GUTTA PERCHA, BALATA. better joint, the seams are either smoothed with a paper folder or hammered with a light hammer having a rounded face, over a mandrel or anvil with a rounded surface. Hollow articles balloons, tubes, etc. are dusted inside with talc to prevent the sides from sticking together. The vulcanization of these articles is also a very simple operation. Rubber toys. The manufacture of these articles has become quite an important branch of the rubber industry, as on account of their indestructibility and softness they are especially adapted for children's use. Human figures, for instance, are made from vulcanized rubber by pressing in metallic moulds, so that the figure is obtained in two halves, each a few millimeters thick. These are joined together by rubber solution, so that they form a hollow body, and are then heated. As the enclosed air expands during the heating process, and would cause the figure to burst, a small hole is made in some part of the latter to allow the air to escape. The hole is later on closed by a small rubber plug. Such figures are also made from sulphurized sheets with the use of a type-metal mould. The sheets are cut according to patterns with a pair of scissors in such a manner that the cut surfaces are slightly sloping, which facilitates their adhesion. Before entirely closing the figure, a small quantity of water, ammonium carbonate, or another substance which at the temperature of heating is converted into steam, is poured in. The completed figure is then brought into the mould. The steam evolved exerts ARTICLES FROM SOFT RUBBER. 169 a pressure upon the rubber, and presses it into all the depressions of the mould, filling the latter com- pletely. After vulcanizing, a small hole is made in the figure to admit air, as otherwise the figure would collapse in consequence of the condensation of the steam and the formation of a vacuum. Rubber balls are made in a similar manner. Seg- ments of a sphere are first cut according to pattern from rubber sheet, and then joined together to a ball in a plaster of Paris mould. In order to make the balls very elastic they are, after vulcanizing, filled with compressed air. When taken from the moulds, the balls are perforated with a fine hollow needle, and air is forced in through the latter by means of a small compression pump until a pressure of two or three atmospheres is indicated. The needle is then withdrawn, and the hole quickly closed with sulphurized rubber, which is vulcanized by holding a hot iron close to it. For larger balls with thicker walls, a higher pres- sure may be used, and it is advisable to fill the balls on a cold day in the open air, since the air on becoming warm acquires greater tension. The so-called velours, or velvet balls, are made from gray rubber mass, then coated with a solution of pure Para rubber, and before the latter is entirely dry provided with velours covering. From balls thus treated the air does not escape, and they retain their spherical shape. Hollow articles of any desired shape can also be prepared by using the rubber dough, the prepara- 170 INDIA RUBBER, GUTTA PERCHA, BALATA. tion of which has been described in a previous chapter. The process is nearly the same as that employed in moulding hollow articles from plaster of Paris. The moulds used for the purpose may be made of metal, wood, or plaster of Paris, but when of the last two materials they must be coated, before use, with linseed oil varnish, the coating being re- peated until the moulds absorb no more varnish. Moulds consisting of more pieces than one are put together in the same manner as those used for moulding articles from plaster of Paris, and the rubber dough is then poured into the hollow part. In doing this the mould is swung to and fro in such a manner that the interior wall is covered with the thick fluid mass, and then the excess of dough is allowed to run off. But, with some ex- perience, the latter is not necessary, as a skilled workman can estimate the exact quantity of dough required for a mould of a certain size. To accelerate the evaporation of the solvent from the dough, it is advisable to fit a pipe into the mould through which air is blown into the interior. By this the vapors of the solvent are quickly carried off. Finally, the mould is placed in a warm room to dry. A suitable quantity of finely powdered sulphur or other vulcanizing agent may be mixed with the dough before it is formed into articles, and, if this has been done, it is -only necessary to place the articles which remain in the mould in the heater to vulcanize them. If pure rubber dough has been used, they can be vulcanized by a simple process. ARTICLES FROM SOFT RUBBER. 171 For tliis purpose they are dusted with finely powdered sulphur, and some of it is also blown into the interior of them. They are then heated in the usual manner ; or they are vulcanized by using chloride of sulphur. Small solid balls of vulcanized rubber are re- quired for sewing machines. These are prepared from sulphurized rubber and heated. A peculiar process is used in many factories for manufacturing them from pure rubber. A block of the latter is pressed against a grater, which revolves as quickly as possible, and by this is cut into exceedingly fine shavings which can easily be balled together. Balls are formed from these shavings with the hand. They are tightly pressed in metal moulds, then brought into a somewhat smaller mould and in this subjected in the cold to as strong a pressure as possible. They are very compact, and must be heated to 104 F. to restore to them their elasticity. Balls manufactured in this manner are especially adapted for bearers under powerful stamping- presses, as they drive the stamp back with great force. The small toy baloons belong also to the special- ties of the rubber industry. Very small balloons are made from clear rubber solution. A glass balloon serves as a mould. A certain quantity of solution is poured into this and distributed over the entire inner surface by swinging the mould to and fro, and the excess of solution is then allowed to run off. When nothing more drains off the 172 INDIA RUBBER, GUTTA PERCHA, BALATA. mould is replaced with the neck uppermost and air is blown in to accelerate the evaporation of the solvent. To detach the balloon from the glass, to which it adheres quite tenaciously, the lower edge of it is carefully loosened from the glass and then air blown in between the film and the glass. The thin film, of which the balloon consists, becomes entirely detached from the glass and can be removed in the form of a bag. The rubber sheets prepared upon glass plates, as described in a former chapter, may be used for somewhat larger balloons, such as are employed at meteorological stations for ascertaining the direction of the wind. As most of these balloons have a volume of a few quarts only, they are generally filled with illuminating gas and then closed. Printing rolls for use in dye ivork, etc., are prepared with the simultaneous use of pressure and heat as follows : A tube made of a sheet of sulphurized rubber mass is tightly drawn over the roll of which a cast is to be taken, and firmly wrapped around with cotton cloth so that all depressions are filled up. The entire mass is then vulcanized, and after heating the tube is withdrawn and turned inside out. Letellier and Verstraat make the rubber jacket of the pressure rolls of cloth printing machines of two layers. The metal drum is first wrapped round, 2 millimeters thick, with cotton. Upon this is brought a layer of hard black rubber of 1.6 ARTICLES FROM SOFT RUBBER. 173 specific gravity, and this is coated with softer rubber of 1.3 specific gravity. The total thickness of both layers is 20 millimeters, and the upper layer is accurately turned for printing, and polished with emery. Preparation of rubber threads. The manufacture of threads forms an important branch of the rubber industry, since on account of their elasticity and tenacity, they are extensively used in the fabrication of elastic tissues. How extensive this use is may be understood from the fact that large factories are entirely devoted to the manufacture of materials from which the elastic webbing for shoes is made. Rubber threads may be prepared according to various methods, but their elasticity and toughness depends on the raw material used. It may here be remarked that rubber which has been shredded, masticated, and then brought into a compact mass by rolling, does not possess the solidity and elasticity of the raw material, and, of course, threads manufactured from the former are of a poorer quality than those prepared from the latter. Square cords from crude rubber. The best quality of rubber in the form of bottles, with the thickest sides and of the most regular shapes, should be selected for making such cords. The necks of the bottles are cut off, and the bowl or body is bisected by a cross-cut. The pieces are then examined, and only those having an entirely uniform appearance are selected. Pieces showing large hollow spaces, or an indication of the presence of foreign bodies, must be rejected, they being unsuitable for the purpose. 174 INDIA RUBBER, GUTTA PERCHA, BALATA. The next step is to convert the pieces obtained by cutting up the bottles into smooth, even sheets. This is effected by softening the pieces by continued boiling in Avater, and then placing them between level iron plates in a powerful press and subjecting them to strong pressure for a few weeks, the press being from time to time tightened. As a low tem- perature helps to make the rubber more compact, it is advisable to carry on the work of cutting threads in winter, and to place the presses in the open air. The sheets when taken from the press should be perfectl} 7 smooth and of uniform thickness. They are then brought to the cutting machine. This consists of a shaft upon which the sheet is fixed vertically by means of sharp points. The shaft revolves around its axis, progressing forward at the same time. A knife, moving quickly to and fro, cuts a spiral band from the sheet, the thickness of the band depending on the greater or smaller velocity with which the sheet approaches the knife. A stream of water falls steadily upon the knife to prevent the rubber from sticking to it. The long band obtained by the operation is then cut into square cords. In many factories the neck and bottom of the bottles are cut off, and the remainder softened in boiling water, then drawn over a wooden mandrel covered with a thin layer of rubber. This mandrel while revolving is raised a certain distance and moves against a knife, placed vertically, which cuts a spiral band from the rubber. This is a simpler manner of obtaining a band of crude rubber, ARTICLES FROM SOFT RUBBER. 175 but the cords cut from it are not quite so solid as those manufactured from the pressed halves of the bottles. The bands, obtained by either of these methods, are now cut into cords or threads by machines, as they do the work with much more regularity than is possible by hand, and save a great deal of time. The simplest manner of cutting the bands into threads is between two steel rolls, in the circumfer- ences of which are grooves as broad as the threads to be cut, and so arranged that the upper roll covers every groove in the lower one. The sheet of rubber passing through between these rolls is cut into a corresponding number of equally w r ide threads which are wound upon reels. The dividing of the sheet of rubber by this machine must be called crushing rather than cutting, and, if the threads are to be cut smooth, it is necessary that the edges of the grooves should be extremely sharp. More complicated, but more effective, is the thread- cutting machine, consisting of a horizontal shaft 'with circular knives, separated according to the width of the threads to be cut. Above this shaft, holding the knives, is placed a roll with narrow grooves, into which the knives penetrate slightly. A pair of smooth rolls grasp the sheet to be cut into threads and carry it through between the grooved roll and the knives, which revolve with as much velocity as possible, and out the sheet into a corresponding number of threads. They are then 176 INDIA RUBBER, GUTTA PERCHA, BALATA. passed through between glass rods and wound upon reels. Cutting square cords from prepared rubber. Although threads cut directly from the raw mater- ial are toughest, their use is limited to certain pur- poses, as they cannot be obtained of any consider- able length, and have the further disadvantage of not being vulcanized. Hence for the manufacture of long threads or of threads from vulcanized rubber^ prepared rubber, either by itself or mixed with sul- phur for vulcanizing, has to be used. The sheet from which long vulcanized threads are to be cut is first vulcanized and then cut. At the present time long threads of ordinary or vulcanized rubber are generally prepared from tub- ing which is divided by a spiral cut. The tubing to be cut is fastened upon a wooden mandrel, which fits exactly into the bore of the tube, and this is fastened to a metal screw which gradually moves forward. A knife moving quickly to and fro cuts a spiral strip from the tube, the width of the strip depending on the height of the screw-thread. Rec- tangular threads are obtained by using a screw with threads of less height than the thickness of the walls of the tubing. The machines for cutting threads from tubing have recently been much improved, and threads of any desired thickness can now be prepared by using but one screw. But in whatever manner the threads may be manufactured, it is of the utmost importance that ARTICLES FROM SOFT RUBBER. 177 the greatest care should be used in winding them upon reels to prevent the freshly cut threads from sticking together. Round rubber threads. For certain purposes, round threads are required. They can, however, be manufactured only from rubber which has been changed into a plastic mass by treating it with proper solvents. This plastic rubber is then pressed through a metal plate provided with circular holes. According to Aubert and Gerard's process the purified rubber is cut up into small pieces and brought in contact with carbon disulphide, alcohol, fusel oil, or wood spirit. Neither of these dissolves the rubber, but they disintegrate its particles, so that they can be easily manipulated into a uniform paste or dough. The following is a very suitable mixture for this purpose : Parts. Rubber 100 Carbon disulphide . . . 100 Alcohol, 85 per cent, strong . . 5 The substances are placed in a hermetically closed metallic vessel, and allowed to stand for from 15 to 18 hours. The mass is then pressed through a wire netting with close meshes, which retains the parti- cles not entirely swelled up. The plastic mass, which should be of the consistency of thick paste, is then brought into the moulding apparatus. This consists of a cylinder in the bottom of which 12 178 INDIA RUBBER, GUTTA PERCHA, BALATA. are fitted a number of cone-shaped tubes the bore* which corresponds to the diameter of the threads be formed. A piston, which should fit as accurately as possible in the cylinder, slowly forces the plastic mass out of the above-mentioned tubes. The threads thus formed, on coming from the tubes, first reach an endless band of cotton velvet about 13 feet long. While they are carried away by this band they lose a considerable part of the carbon disulphide by evaporation, and obtain thereby a certain degree of solidity. From the velvet band they pass to a second endless band of fine wire gauze which is kept in a shaking motion, while finely powdered talc falls constantly upon the threads. By the shaking motion of the band, the threads are covered everywhere with the talc powder, which prevents them from sticking together. To entirely evaporate the carbon disulphide which may still adhere to them, Aubert and Gerard use a system of endless linen bands consisting of five bands, each about 52 feet long. They are arranged one above the other and move in opposite directions so that the threads run to and fro. About ten minutes are required for them to run over all the endless bands, and during this time they lose sufficient of the carbon disulphide that they can be wound upon reels without sticking together. They are wound in the same manner as the loose cotton bands in cotton mills. Funnels stand over vertical tin boxes which all revolve around their ARTICLES FROM SOFT RUBBER. 179 axes at the same velocity. The thread glides through the funnels into the boxes and is wound up in it to a spiral. When the cylinder from which the plastic rubber is forced is nearly empty, it is filled up again, and in this manner threads of any desired length can be manufactured. If threads of a specific diameter are to be prepared, the fact must be taken into con- sideration that the diameter of the threads de- creases considerably in drying. A thread pressed through a tube having a diameter of 0.039 inch, when dry will have a diameter of only 0.028 inch. Only threads having at least the diameter men- tioned above can be prepared by pressing. If holes of a smaller diameter than 0.039 inch are used, the plastic mass breaks constantly and the work cannot be carried on without interruption. A peculiar physical behavior of rubber is taken advantage of for preparing still thinner threads. Namely, if a thread of rubber is stretched length- wise and simultaneously exposed to a temperature of 239 F., it will retain the length to which it has been stretched even after the tension ceases. If the thread which has been dried in this manner is again drawn out lengthwise, and again heated to 239 F., it remains stretched, and by several times repeating this operation threads of a much smaller diameter can be obtained than is possible by cutting or pressing. Rubber hose. This forms a very important com- mercial article, as on account of its pliability and 180 INDIA RUBBER, GUTTA PERCHA, BALATA. resistance to chemical agents, it is used in many industries. The demands made in practice on rubber hose are manifold, and frequently it is not easy to come up to them. Hose or tubing for chemists' use and for conduct- ing illuminating gas should be as thin and pliable as possible, and at the same time impermeable to gas. Hose for conducting compressed air, an in- dispensable component of rock drills, should be able to withstand a pressure of several atmospheres. It is absolutely necessary that hose which shall answer all reasonable demands should not kink when used in short bends. Such kinking is very annoying, as it obstructs the flow of the fluid or gas contained in the hose until it is again straight- ened out, and subjects the manufacturer to the charge of furnishing unserviceable goods. This defect is found chiefly in hose the walls of which are too thin, and can be avoided by maintaining due proportion between the diameter and the walls of the hose. Manufacture of ordinary rubber hose. It is now customary to manufacture hose from vulcanized rubber, it being more servicable than that from ordinary rubber, which soon becomes brittle and full of cracks, especially when frequently exposed to changes of temperature. A plastic mass, obtained by mechanically treat- ing a compound of rubber and sulphur, is used for making hose. The mass is first rolled into sheets of a thickness corresponding with that of the walls ARTICLES FROM SOFT RUBBER. 181 of the hose which is to be prepared, the interior diameter of the latter being determined by an iron core over which the plastic mass is shaped. Cores of round smooth wire are generally used for hose of a small diameter, but for hose of a larger diameter wooden cores are preferred, since iron cores, on account of their weight, are difficult to handle. But the wooden cores must be perfectly cylindrical, and it is advisable to saturate them, before use, with hot linseed oil. For manufacturing short tubing the plastic mass is cut into bands somewhat wider than the circum- ference of the core. These bands are then placed around the core and joined together by gentle pressure. Finally the core with its envelope of rub- ber is rolled upon a smooth table to give the tubing a perfectly cylindrical form. It is then wrapped in a linen cloth which remains around it during vulcanizing. When taken from the heater, the core is withdrawn, and the linen cloth removed from the tubing, which is now finished. If hose of greater length or larger diameter is to be manufactured, the rubber is generally used in the form of a band, w r hich is laid in spirals around the core in such a manner that the edges slightly overlap. By pressing with the fingers and rolling upon the table, they are joined together to a hose which is treated in the same manner as has been described. But rubber alone is not sufficient where the hose lias to bear a great pressure, and it becomes neces- 182 INDIA RUBBER, GUTTA PERCH A, BALATA. sary to strengthen it by intermediate layers of tissues and spirals. Of course this increases the solidity, but decreases the flexibility of the hose to a great degree. Rubber hose with intermediate layers or stiffeners. Hose with an intermediate layer of tissue is pre- pared by first forming a thin hose from plastic com- pound. A piece of the tissue is placed over this, but this must be wide enough to allow the ends to lap over. The tissue before it is laid upon the hose is brushed over with a solution of rubber, and in placing it in position, great care must be observed to prevent the formation of air bubbles, as on the places where such are present, the rubber and tissue do not unite, and experience has shown that, when the hose is subjected to a high pressure, it bursts first at those defective places. When the tissue has been applied, it is covered with a second layer of plastic compound, so that it is entirely inclosed and can only be seen on the cross-section. For hose with layers of wire, the latter is used in the form of spirals, which are wound over the hose formed on the core, and then covered in the usual manner with a second layer of rubber. Small hose can also be manufactured with the machine used for pressing threads. But in this case the cylindrical holes through which the plastic rubber is forced are replaced by openings in which cores of suitable size are inserted. The latter arc hollow, and are connected with a vessel containing ARTICLES FROM SOFT RUBBER. 183 water. The small hose as it comes from the cylinder is closed by pressing the ends together, and filled with water as quickly as it is formed. This is abso- lutely necessary, as the hose would collapse if this precaution were neglected, and the sides stick together. The subsequent treatment of the hose is exactly the same as that of the threads. When it is finished, it is opened and the water allowed to escape. Tubing machines of various sizes are manufac- tured by John Royle and Sons, of Paterson, N. J. Fig. 11 shows their tubing machine No. 2, which is well adapted to making the larger sizes of tubing, such as fire-hose lining, etc., and for making various shapes of a greater size than can be conveniently handled in smaller machines, which are more suit- able for syringe and flower tubing and various small-sized druggists' and stationers' sundries. The most important feature of a tubing machine is the cylinder, upon the construction of which the harmonious working of the various parts depends, as it is in the cylinder that the heat necessary for the proper working of the compound is applied. Nearly all the different tubing compounds are highly sensitive to the action of heat, and require to be subjected to various degrees of temperature at different points while passing through the machine. To produce the heat in sufficient quantities, and under perfect control as to direction and extent, has been the main object aimed at in the construction of the cylinder in the Royle machines. Thus when working india rubber or other similar material, it 184 INDIA RUBBER, GUTTA PERCHA, BALATA. is necessary to heat the head and cylinder so as to soften the mass and facilitate its delivery through the die, and it is also essential that the degree of heat applied should be readily controllable in order FIG. 11. that the consistency of the material may be so regu- lated that it will become sufficiently plastic to mold readily, and at the same time retain the form given to it by the die. To effect this result it may be ARTICLES FROM SOFT RUBBER. 185 necessary, in some cases, to heat both the cylinder and the head, while in others it may be necessary to heat only the cylinder and cool the head, or to cool both cylinder and head. To provide for all con- tingencies, both head and cylinder are jacketed, and equipped with a steam-chest having separate com- partments for steam and hot water. Suitable pas- sages issue from these compartments for conveying the steam and water directly to the cylinder and head, and an arrangement of valves is provided, by means of which the flow of water and steam can be regulated, and any desired temperature maintained. The passages and valves are arranged as integral parts of the machine, and no external pipes or con- nections are needed, except the main supply and discharge pipes for conducting the heating and cooling fluids to and from the valve-chest. The bore of the cylinder has a suitable lining, so arranged that, in the event of wear, it can be replaced at a nominal cost. The head for holding the dies, etc., for giving the desired form to the material as it issues from the machine, is so arranged that dies, cores and core- bridge can be readily removed from the front of the machine without disturbing it. It can, however, be readily detached, when desired, by simply loosen- ing the nuts on the stud-bolts by which it is attached to the cylinder. The dies which give form to the outside of the compound as it issues from the machine are made in two styles, thimble and thread, and are hel< 186 INDIA RUBBER, GUTTA PERCHA, BALATA. place in the machine by means of holders which screw into the head from the front. The thimble dies are fitted into the bore of the holder from the back and are held in place by a rim of metal, while the threaded dies are hexagonal-shaped on the out- side and have a threaded stem which screws into the holder from the front. The holders for both styles of dies are graduated in size, so that each holder will accommodate a series of dies of different sizes. Thus, with very few holders, a large assort- ment of dies can be used. The cores used in making tubing are secured between the head and cylinder by a core bridge. As the core must, of necessity, be concentric with the die in order to insure uniform thickness in the tubing, an adjusting device is provided, by means of which the position of the core can be easily regulated. This device consists of four screws placed at regular intervals around the core bridge and bearing on it at different points of its circum- ference. By simply tightening or loosening these screws, the core-bridge and core can be readily secured in any desired position and perfect alignment with the die maintained. This provision for main- taining absolute relative accuracy between the die and the core is an important feature of the machine. The method of adjusting from the core-bridge instead of from the core itself, together with the axial adjustment of both die and core, renders it possible to maintain perfect alignment without deflecting the core or impeding the flow of the compound. ARTICLES FROM SOFT RUBBER. 187 The rubber or other raw material is fed into the cylinder through an opening at the back, and is then carried along and forced through the die by a powerful Archimedean screw or stock-worm which extends along nearly the entire length of the cylinder, and is turned by powerful worm or spur gearing, as the case may be. This stock-worm is made of steel, and is very durable; the walls of the threads being of sufficient thickness to withstand the wear and tear of constant use for an unusually long time. As it is sometimes desirable to change the worm in use for one of different capacity, these machines are so arranged that the stock-worm in use can be removed and another substituted without difficulty. A valuable feature is the carrying belt, or apron, for conveying the tubing or other product from the die. without stretching or distortion. This apron extends from immediately beneath the die to a re- volving pan, or other appropriate receptacle, placed on the floor at a suitable distance from the machine. It is supported by an adjustable arm extending from the machine, and the driving mechanism can be so adjusted as to make the delivery of the tubing from the die and the movement of the apron synchronous. This receiving apparatus is a distinctive feature of the Koyle machines, and adds materially to the quality of the finished product, as it not only pre- vents distortion and wrinkling, but also allows the soft and impressible gum sufficient time to harden somewhat before being delivered into the pan. This 188 INDIA RUBBER, GUTTA PERCHA, BALATA. * is an advantage that practical makers of rubber goods will readily understand. Rubber sponge or moss rubber. This peculiar pro- duct was first manufactured by P. W. Cow, Hill & Co. The mode of manufacture is still kept secret, but is said to consist in repeated vulcanization, softening and pouring into moulds, the resulting product being a sort of sponge more or less cellular and porous like a sponge, and possessing the prop- erty of absorbing water and allowing it to escape when pressed. Dr. Wiederhold is of the opinion that rubber sponge is prepared as follows : A solu- tion of rubber in carbon disulphide, or chloroform, or benzene, is quickly heated, whereby the last remnants of the solvent distend the mass, which has become very viscous, and thus imitate the cellular structure of sponge. According to other experiments, rubber sponge may be produced as follows : A tall tin vessel of prismatic shape is filled a few T centimeters deep with rubber solution and the latter heated to above the boiling-point of the solvent used in the prepara- tion of the solution. In consequence of the evap- oration of the solvent, the mass becomes more and more viscous, and as the steam bubbles force their way through it with constantly increasing diffi- culty, the final result is a very porous and cellular product. By using rubber dough and heating very slowly, sponge with very fine pores is obtained which as regards softness, by far surpasses the finest bathing sponge. The finished product is ARTICLES FROM SOFT RUBBER. 189 vulcanized by plunging it into a solution of chloride of sulphur, and may be further provided with a suitable base of hard rubber so as to make it handy for use. However, the disagreeable odor of these sponges, which is perhaps more perceptible on account of their porous nature than is the case with other vul- canized rubber articles, prevents their general use. This odor can, however, to some extent, be over- come by the use of animal charcoal. The sponges are simply wrapped up in tissue paper and placed in a vessel filled with powdered animal charcoal. In a few weeks, especially if the vessel be put in a warm place, the sponges will have lost nearly all odor, and the last traces of it may be removed by washing.- These rubber sponges have been highly recom- mended for washing horses, they having the ad- vantage over the curry-comb of not injuring the skin of the animal or tearing out hair, while at the same time the dust is completely removed and a beautiful lustre is imparted to the hair. In the form of brushes, provided with a hard rubber back, they have been recommended for cleaning clothes, cloth, ribbons, fine tissues, such as velvet, etc. Rubber shoes. In the course of time this article has passed through a peculiar process of develop- ment. The first so-called gum shoes consisted of a single piece of rubber and were made in the same manner as the bottles of crude rubber. Clay moulds in the shape of a last were coated with the 190 INDIA RUBBER, GUTTA PRRCHA, BALATA. latex and dried over a fire. The congealed coating was then drawn from the last and formed the shoe. Shoes prepared in this manner were very durable, but ugly, and had the further defect of enclosing the feet tightly and producing in them in a short time a feeling of almost unbearable heat. Later on shoes were made by cementing together pieces of rubber, but these had the defect of soon losing their elasticity. Goodyear was the first to make shoes of vulcanized rubber, and the extent of the present manufacture may be judged from the fact that a single factory turns out 3000 pairs a day. It may, however, be mentioned here that under the name of rubber shoes, products are brought into the market which do not deserve the name, as no rubber whatever is used in their manufacture, but only elastic varnish colored black. Genuine rubber shoes are made as follows : A tricot-like tissue is coated by passing through be- tween rolls with a thin layer of sulphurized rubber colored black with lamp-black. The separate parts which are to form the shoe are cut from the sheet thus prepared, the sole being cut from a somewhat thicker sheet, and cemented together with rubber solution over hollow iron lasts. They are 'then coated with asphalt lacquer and vulcanized over .the last. Bicycle tires. Pneumatic tires for bicycles, etc., may be divided into two classes : Single-tube tires, in which an endless tube is made air-tight and sufficiently strong to resist the air pressure, and ARTICLES FROM SOFT RUBBER. 191 compound tires consisting of two parts an inner air tube and an outer cover. Single tube tires are formed of alternate layers of more or less pure rubber and strong cloth or canvas. The interior is made of pure or nearly pure rubber, the object of its introduction being to form an absolutely impervious surface to the pas- sage of air. The strength of this inner layer is practically nothing, its principal office being to fill the interstices found in the material surrounding it, and which possesses the necessaiy strength to resist the inflation by the air. Mr. Henry Sturmey divides compound tires into five classes according to the mode of adjustment of the outer cover to the rim, viz : Solutioned tires, w r ired tires, interlocking and inflation-held tires, laced tires and band-held tires. It would lead too far to describe all these classes of tires, and hence only a description of the original " Dunlop " tire, with which originated the principle of air tubes for cycles, will be given, and of the Morgan and Wright tire, both of which belong to the solu- tioned type of tires. In the Dunlop tire the outer cover consists of a thick tread of rubber solutioned to a canvas strip. A complete woven tube of canvas encircles the air tube and is solutioned to the rim, which is previously wrapped round by a canvas strip, while the flaps of the outer cover are solu- tioned to the inner surface of the rim, one flap being hipped over the other, the side being split to pass the spokes. A strip of canvas solutioned over the flaps, makes a neat finish. 192 INDIA RUBBER, GUTTA PERCHA, BALATA. In the Morgan and Wright type, the air-tube is butt-ended, or rather scarf-ended, the two ends over- lapping each other about eight or ten inches. The outer covers form practically a tube slit for a few inches along its under side. This opening serves for the insertion of the air-tube, and is laced up when the air-tube is in place. When partially in- flated the tire is cemented on the rim. Manufacture of water-proof tissues. There are two kinds of water-proof tissues, known as double text- ures and single textures. The first consist of two layers of the same or different stuffs cemented to- gether by a thin layer of rubber. Single textures consist of a single tissue which is coated with rub- ber either only on one side (single face) or on both sides (double face). Rubber was first used in the manufacture of water-proof tissues by Charles Macintosh, and the material was called by the name of the inventor. It possessed the advantage of being very durable, but on the other hand had the disadvantage of being very weighty, thick and expensive. It was prepared by placing a thin sheet of rubber between two tissues and passing the whole through between heated rolls. By this manipulation the rubber was so strongly heated that it became soft, and was pressed into the meshes of the fabrics, cementing them firmly to- gether. Many experiments were made to improve Macintosh's process by decreasing the weight and thickness of the materials, but this has only been ARTICLES FROM SOFT RUBBER. 193 accomplished since the introduction of the new pro- cess of working rubber, which renders possible the preparation of very thin sheets. Dumas suggested the preparation of very thin sheets by allowing a solution of rubber in ether to run down over heated rolls. The ether would thereby evaporate and the soft thin sheet remaining behind, which could readily be detached from the polished rolls, was to be spread upon the tissue. The latter was to be covered with a second layer 01 tissue and the whole cemented together by rolling. It is absolutely necessary that the layer of rubber should be as thin as possible, if it is desired to pre- pare an article which will answer all reasonable demands. So much progress has been made in cutting cylinders of rubber into thin sheets, that they can be furnished not much thicker than a sheet of writing paper. A successful attempt has been made to coat only one side of a tissue with such thin sheets, but this unfortunately has the disadvantage of making the material heavy, and of being rather expensive. A decided improvement in the manufacture of water-proof materials has only been made since the process of obtaining rub- ber in a very soft form by mechanical treatment became known, but the greatest perfection in the manufacture of this important article has only been reached since the introduction of vulcanized rubber. The first improvement in Mackintosh's process consisted in the use of but one layer of tissue, and by making the sheet of rubber as thin as possible, 13 ^ 194 INDIA RUBBER, GUTTA PERCHA, BALATA. the bulk of the material was considerably decreased. The manner of manufacturing these water-proof fabrics was very simple, and was carried on as fol- lows : The crude rubber was first converted into as homogeneous a mass as possible by passing it through between rolls, and was finally rolled into very thin sheets. When the latter are "taken from the rolls they are quite sticky, and this is made use of for cementing them to the tissue, which is ac- complished by placing the fabric upon the sheet- of rubber and passing the whole through between rolls. Before entering upon the discussion of the more modern methods of making water-proof fabrics, a few words may be said about the character of the tissues to be employed. The material may be either silk, wool or cotton ; as the tissue is simply the bearer of the substance which renders it water- proof, either loosely or closely woven fabrics may be used. In the first case a considerable quantity of rubber is required for water-proofing, and in the latter only a small quantity. Most manufacturers have found it best to use closely woven fabrics for water-proof tissues, as these require less rubber and besides have the advantage of being firmer. Therefore strong cotton goods are generally used at the present time for finer articles, such as water-proof coats and cloaks. The principal requisite of such materials is that they should be as even and smooth as possible, since ARTICLES FROM SOFT RUBBER. 195 even the smallest knot in the tissue exerts an in- jurious effect upon the quality of the goods to be manufactured. At the present time, as has been mentioned, very thin coatings of rubber can be prepared. If there should be knots in the tissue they would, of course, be covered with rubber and the fabric would seem to be of excellent quality as long as it is not used. But, if a garment made of such material is used for a short time, the rubber will commence to peel 'off wherever the knots are. Fabrics of cloth and vulcanized rubber can be prepared by rolling the soft compound of rubber and sulphur into very thin sheets and passing them together with the cloth through between heated rolls. The object of heated rolls is to force the rubber compound firmly into the meshes of the tissue, and, if the proper temperature be used, at the same time to vulcanize the rubber. One pair of rolls, heated to the temperature re- quired for vulcanizing, may suffice for the work, but very careful arid skilled workmen are then re- quired. Experience has shown that it is much better to use two pairs of rolls, the first pair of which is heated at the utmost to 248 F., while the second is heated to the temperature required for vulcanizing the rubber compound. Finally, the finished fabric is rolled upon cylinders as soon as it has become sufficiently cooled off, and should be further worked as soon as possible. It is, however, difficult to obtain uniform pro- 196 INDIA RUBBER, GUTTA PERCHA, BALATA. ducts in this manner, and experiments have, there- fore, been made to use vulcanized rubber. But as this, as is well known, cannot be cemented to- gether, and will not combine with the tissues by pressing, it is necessary to have recourse to certain manipulations to obtain the desired object. According to the method recommended by John- son, very thin sheets of vulcanized rubber are pre- pared, and these partly desulphurized by boiling for some time in caustic soda. After they have been boiled, they are first washed in water contain- ing some hydrochloric acid (to remove the last traces of the alkali), next in pure water, and then dried. The sheets, thus prepared, are roughened by passing them over a roll covered with emery paper and revolving with great speed (800 to 900 revolu- tions a minute). The object of this is to facilitate the union of the rubber with the tissue. The sheet is then coated with a rubber solution and placed upon the tissue and both together are passed through between the rolls in order to cement them together. The articles manufactured in this manner are of excellent quality, but, on account of the process being so very complicated, rather expensive. Since the method of completely dissolving rubber has become known, solutions, or a paste of it, are almost exclusively used for the manufacture of water-proof tissues, and these are generally only coated on one side. ARTICLES FROM SOFT RUBBER. 197 Although the work seems to be very simple when solutions are used, nevertheless many difficulties present themselves in the execution of the operation. Frequently the very volatile oils, which are ob- tained by distilling coal tar light coal-tar oil or naphtha are used as solvents on account of their cheapness. It is true that these solvents volatilize very quickly, but they are mostly always mixed with small quantities of less volatile products, which remain behind after the volatilization of the lighter oils, and the odor of which adheres to the rubber so that it is perceptible for years. This odor agreeable to no one is so repulsive to some per- sons that they will not use a garment manufactured from such tissue. A further evil of using pure rubber solutions is that the layer of rubber, which is left behind, re- mains sticky for some time, and, for this reason, a garment, prepared from it, cannot be folded up, as the surfaces would stick together so tight that the folds could not be separated. All these evils are now removed by using a rub- ber paste which also contains the substance re- quired for vulcanization, and by subjecting the freshly coated tissue to the heating process. Such solutions, or more correctly speaking, such compounds, used for this purpose are at once mixed with the quantity of sulphur required for vulcaniza- tion. The simplest manner of doing this is to sat- urate the carbon disulphide used for dissolving the rubber with sulphur, or by working very finely 198 INDIA RUBBER, GUTTA PERCHA, BALATA. powdered sulphur into the mass. The principal requisite for a correct execution of the work is, that the mass should be entirely homogeneous, a prop- erty which can be imparted to it by a suitable mechanical treatment, as has been explained in a previous chapter. For spreading the rubber compound upon the tissue as uniformly as possible and to cement both together, a special machine is required. It makes FIG. 12. very little difference which of the various makes of machine is used, as they all answer the purpose for which they are intended, a thoroughly experienced workman being the principal requisite for the work. A spreader well adapted for all purposes is shown in Fig. 12. Two rolls of small diameter, generally 7 to 7{ inches, rest in brasses upon a suitable frame. The ARTICLES FROM SOFT RUBBER. 199 lower roll is made to revolve and is set in motion by cog-wheels and the crank K, with which they are connected. The upper roll has square arbors which fit into the brasses, and therefore it does not revolve. The object of the upper roll is to regulate the thickness of the solution which is to be spread upon the tissue, and for this purpose is provided with a peculiar mechanism. Two levers, H, H, having their fulcrum at b, and loaded with weights G, press with a certain force the upper roller against the lo.wer one, this force increasing in power the more horizontal the position of the levers becomes. As may be. seen in the accompanying illustration the levers are double-armed, and on the other end are connected with chains, which can be wound upon pulleys. The less the pressure shall be, which is to be exerted upon the upper roller, that is to say, the thicker the rubber compound is to be spread upon the tissue, the tighter the chains are drawn, and the more the arm of the lever, pro- vided with weights, is raised. The tissues to be converted into water-proof fab- rics are wrapped around a roller, and are wound upon a cylinder after they have been provided with the solution, and sufficiently dried, so that the sep- arate folds will not stick together. As has previously been mentioned, the more closely woven the fabric is, the thinner the rubber compound can be spread upon it, and there is no 200 INDIA RUBBER, GUTTA PERCHA, BALATA. danger of soaking through, which must by all means be avoided. For tissues with a looser text- ure, a rubber compound of greater consistency has to be employed, as thin solutions would soak through. The thinner the rubber compound is, the more beautiful and uniform the coating will be, and for this reason it is necessary to apply several coatings to the tissue to render it entirely water-proof. For the first coat the compound should be of sufficient consistency to prevent all danger of soaking through. In many factories the solution or com- pound is still applied by means of ladles, which a workman fills from a vessel containing the material. As the tissue advances between the rolls, he pours the solution upon it, and it will be readily under- stood that considerable skill is required to pour the solution in such a manner as to spread exactly the right quantity. And, as besides the solutions always contain fluids, the vapors of which exert an injurious effect upon the health of the workmen, the manufacture of water-proof tissues in this primi- tive manner deserves to be called very unhealthy work. To protect the workmen from the evil effects of the vapors, the tissue, after it has been coated, is brought into a room from which the vapors are constantly pumped. But this gives only temporary protection, as the workman who ladles the fluid from the vessel and spreads it upon the tissue, to be sure, does not suffer ARTICLES FROM SOFT RUBBER. 201 from the vapors which are formed behind the rollers, but is exposed to those developed on the other side of the apparatus. A very simple contrivance, represented by Fig. 13, may be used for removing this evil, and at the same time for spreading the mass as uniformly as possible upon the tissue. This apparatus consists of a sheet-iron box K, having the shape of a three- sided prism, which serves for the reception of the solution or compound. The box is placed imme- FIG. 13. diately behind the rolls W. The lid of the box catches into a gutter filled with water, which pre- vents the escape of vapors into the workroom. A cock, H, is fitted into the lid, which is only opened at the commencement of the operation, and allows air to enter into the interior of the box as soon as the contents commence to run off. On the lower edge of the box is a slide which closes a slit in the box through which the fluid escapes. Close to the rolls stands a sheet-iron case, G, hav- ing the form of a house with a steep roof. It is 202 INDIA RUBBER, GUTTA PERCHA, BALATA. somewhat wider than the tissue which slides along upon the bottom of it, and passes out through as narrow an opening as possible. On top of the roof is a pipe, R, provided all around with fine holes, and connected with a reservoir constantly filled with cold water. On the sides of the box are several pipes for carrying off the fluid dripping down. The apparatus works as follows : A stream of the solution as wide as the tissue to be coated flows through the slit in the vessel, which has been opened just as wide as it is necessary, the rolls spreading it upon the tissue in an entirely uniform layer. The part of the bottom of the box nearest to the- rolls, into which the tissue passes, is heated by hot water contained in the pipes S. Evaporation of the solvent commences at once, and the vapors rise up to the roof. But this is con- stantly cooled off by the water falling down like rain, and the vapors, on coming in contact with the cold surface, are condensed, or at least the greater part of them, and run down on the inside of the box, and escape from it through the discharge-pipes, the fluid being' collected in flasks placed under them. The best plan is to arrange the work so that the manufacture of water-proof tissues can be carried on in the cold season of the year. The rolls and the vessel containing the solution should then be put in a heated room, while the sheet-iron box, in which the solvent is condensed to a fluid, is placed in the ARTICLES FROM SOFT RUBBER. 203 open air. With such an arrangement the workmen do not suffer from the injurious vapors, the work can be carried on without interruption, and the greater part of the solvent may be regained. As a certain quantity of the solvent still adheres to fabrics which have recently been finished, arid causes them to be sticky, it is advisable not to wrap them up immediately after they come from the apparatus, but to keep them stretched out for several days as smoothly as possible. If tissues for the manufacture of garments are to be prepared, a certain quantity of lampblack is added to the rubber compound before its mechan- ical treatment is commenced, and worked with it for the purpose of imparting a uniformly black color to it. A coating of light brown color is obtained by using rubber in a pure condition. By mixing it with sulphur and heating the ready tissue to the temperature required for vulcanization, the coating will show the peculiar gray coloring of vulcanized rubber. Tissues with an intermediate layer of rubber. Cut sheets of rubber are no longer used for manufactur- ing such water-proof fabrics as were first made by Mackintosh, solutions being now generally em- ployed for the purpose. The tissues are cemented together with the assistance of an apparatus shown in Fig. 14. The tissues having been wound upon the cyl- inders W, are unrolled in the direction indicated 204 INDIA RUBBER, GUTTA PERCHA, BALATA. by the arrows and pass through between two rolls placed in a horizontal position. A vessel resem- bling the one represented in Fig. 13, contains the rubber solution, and is placed exactly over the rollers. The solution is allowed to run from this vessel by opening the slide in the bottom of it as wide as may be necessary, and on reaching the tissues, it is forced into their meshes by the rolls. A second pair of rolls, placed beneath the others FIG. 14. and heated by steam, effect the evaporation of the solvent. The finished tissues are hung up for a few days to allow them to become completely dry. Deodorizing water-proof fabrics. The odor of the solvent adhering for a long time to tissues water- proofed by means of pure rubber, it becomes neces- sary to remove this odor as much as possible. Ex- posure to a higher temperature, even for a longer time, is not sufficient for the purpose. More satis- ARTICLES FROM SOFT RUBBER. 205 factory results are obtained by constantly changing the air in the heated chamber in which the tissues are suspended, for instance by conducting a current of hot air through it. It is a well-known fact that certain bodies which volatilize with great difficulty when left to them- selves, do so very readily when brought in contact with hot steam, and this process may be used for removing the disagreeable odor from tissues coated with pure rubber. The simplest plan is to use the saturated steam as furnished by the steam boiler of the factory. The tissues are suspended in a properly arranged room, and the steam is passed into the latter through sev- eral openings. A rather narrow escape pipe for the steam is placed at the other end of the room, and provision must be made for the escape of the con- densed water. A pressure of but little more than one atmosphere is sufficient for all purpose's, and the tissues will be entirely deodorized after they have been exposed for some time to the action of the steam. Oil of turpentine is frequently employed for dissolving the rubber, especially for goods of an inferior quality. This solvent contains small quan- tities of empyreumatic substances of a very disagree- able odor, and the latter adheres so tenaciously to the fabrics, as to render its removal difficult by the treatment with steam, and a slight odor always remains behind. This applies also to coal-tar oils, and for this reason these solvents should be tested before use, 206 INDIA RUBBER, GUTTA PERCHA, BALATA. and those possessing a disagreeable odor in a re- markable degree should either be entirely rejected or subjected to a second rectification in order to separate as much as possible the objectionable pro- ducts. Manufacture of water-proof fabrics by means of rub- ber compounds. The use of pure or vulcanized rub- ber for the . manufacture of water-proof fabrics is rather expensive, since, besides the labor required, a large portion of the solvent is lost even with the use of all imaginable precautions. In order to manufacture water-proof fabrics at a smaller cost, less expensive bodies than rubber are partly used, and in some cases this material is entirely omitted in the composition. Coal-tar and boiled linseed oil have proved good substitutes for a part of the rubber, as they furnish compositions quite suitable for many purposes, for instance, for so-called rubber shoes, they being at present more frequently used for this purpose than pure rubber. For the preparation of compounds which, besides rubber, are to contain linseed oil, the latter is heated until decomposition takes place. For this purpose it is brought into a boiler of a sufficient capacity to contain at least three times the quantity of oil, as the latter expands very much during heating. The oil should be heated as quickly as possible to from 302 to 320 F., and kept at that temperature for several hours. The fire is then increased to such an extent that the oil apparently boils, this ARTICLES FROM SOFT RUBBER. 207 being the stage of its decomposition. The heating is continued until a sample taken from the boiler with a wooden spatula runs off in long, viscid threads. The oil thus prepared possesses the properties of a quickly-drying varnish, and until it is used must be protected against the action of the air to prevent it from drying in. For this purpose, after it has become cold, it is put in a vessel, and is covered with a layer of water. The purified rubber is dissolved in oil of turpen- tine, which is generally used as a solvent in this case, and the solution compounded with a certain quantity of boiled oil, the latter depending entirely on the pleasure of the manufacturer, as the solution can be mixed with any desired quantity of it. When the first coating is dry, a second or a third is applied, as may be found necessary, and finally one consisting of boiled oil alone, to which has been added some lampblack or any other coloring matter. The tissues can be coated by using the same apparatus employed for preparing fabrics with pure rubber, or by stretching them over a frame and applying the composition with a flat brush. When such tissues have been prepared with proper care, they are especially well adapted for the manufacture of rubber shoes. The separate parts of the shoes are cut from it according to patterns, and cemented together over a last with rubber solu- tions. The soles are manufactured either of vulcan- ized rubber or may be made of the same tissue, but 208 INDIA RUBBER, GUTTA PERCHA, BALATA. in the latter case either very thick tissues are used or several layers of the fabric, employed for the uppers, are joined together by pressing them while they are still sticky, in order to make the soles more durable. If it is desired that the boiled oil should dry as quickly as possible, a small quantity of sugar of lead is added to it before it is boiled ; one per cent. of the weight of the oil being sufficient for the purpose. When coal tar is to be added to the rubber, it must first be boiled, until a mass of the consistency of Burgundy pitch is formed. While still hot, it is kneaded together with and worked in the same manner as pure rubber. This composition can be vulcanized* by adding sulphur to it during the mechanical treatment, and subjecting it to the heating process, but the quantity of sulphur added must be somewhat larger than that required for pure rubber. Water-proof tissues may also be prepared by using a rubber lacquer, which will be described later on. In regard to pliability and lustre, the quality of the coating will largely depend on that of the varnish used. Rubber felt, felt paper, or Clark's patent felt, is used for a variety of purposes, such as covering damp walls, protecting silk and other wares from damp- ness during water-transit, covering telegraph wire, roofing, etc. Although rubber is now used, gutta- percha, alone or mixed with resins and other mat- ARTICLES FROM SOFT RUBBER. 209 ters, has been employed. A pair of ordinary mix- ing rolls, running at equal speeds, receive over each a cotton fleece, which is delivered from the carding machines stationed on opposite sides, so that the two fleeces enter together between the rolls, and passing down through an opening in the floor are led away or rolled up. A sort of dough is carefully laid between the rolls, and as the fleeces pass through, the rubber is squeezed into them. The fabric is vulcanized by incorporating sulphur with the rubber mixtures, and heating in the same way as ordinary spread fabrics. If made with a good quality of rubber and naphtha, it should not feel clammy nor soft, but should be dry and tough. Paper can be similarly treated, and for damp walls, etc., would in many cases be as useful as cotton, while much cheaper. Fabrication of elastic webbings. Genuine elastic webbing can only be manufactured with the use of rubber. Sheets or threads of the latter material may be employed, though sheets are only of secon- dary importance, threads being chiefly used for the larger portion of these fabrics. For the manufacture of elastic webbings with the use of sheet rubber, closely woven tissues, the individual threads of which possess a considerable degree of elasticity, have to be employed. The tissues are stretched over a frame brushed over with rubber solution, and then covered with a sheet of rubber which has been stretched in the same manner as that used for threads previously de- 14 210 INDIA RUBBER, GUTTA PERCHA, BALATA. scribed. Upon this sheet is placed the second tissue, also previously brushed over with rubber solution. When dry the fabric thus prepared is exposed to a temperature of from 140 to 158 F. in order to restore the elasticity of the rubber. Sheets of vulcanized rubber, if used, must first be partly desulphurized and roughened with pumice stone to make the solution adhere to them. They are then worked in the same manner as above described. The threads to be used for webbing must first be subjected to stretching. For this purpose they are placed in warm water and allowed to remain there for some time, whereby they acquire a great degree of ductility. They are then wound upon reels, being strongly stretched during the process, and exposed to as cold a temperature as possible, until they have lost all elasticity. For this reason it is advisable to arrange the work so that the operation of stretching the threads can be dono in the cold season of the year. Threads, which have been properly stretched and cooled off, should not contract when taken from the reels nor show any perceptible elasticity. Should a thread break during stretching, the ap- paratus is stopped, the place of rupture cut obliquely with a pair of sharp scissors, and the freshly cut surfaces joined by pressing them together. The weaving of rubber threads is done by form- ing a kind of net consisting of six or seven threads of any kind of yarn around each thread, and these ARTICLES FROM SOFT RUBBER. 211 overspun threads are then joined together by a woof. They may also be wound upon the beam as a chain and provided with a woof of ordinary yarn. Another method of preparing elastic webbings, but furnishing a less durable article, consists in placing the threads parallel along-side of each other upon a tissue which has been brushed over with rubber solution, and covering them with a similar tissue. They are then cemented together by pass- ing them through between powerful rolls. Tissues prepared in either manner are finally finished by passing them through between rolls heated by steam, which impart to them a tempera- ture of from 140 to 158 F. The rubber having become inelastic by exposure to a low temperature, assumes by this its original elasticity. The stretched threads contract and effect also the contraction of the tissue joined with them. When threads of vulcanized rubber are to be used in the manufacture of elastic webbing, the process must be changed in a corresponding manner, as vulcanized rubber does not possess the property of retaining the length given to it by stretching, but will contract to its original length when the tension is discontinued. In this case the loom must be so arranged that the threads are firmly stretched while they are woven and the finished woven material must also be subjected to such tension. The power acting upon the tissue is only released when the latter is 212 INDIA RUBBER, GUTTA PERCHA, BALATA. entirely finished, when it will contract to the orig- inal length of the threads. Recovery of solvents. For the recovery of vapors of henzene, naphtha arid other very volatile fluids used in the manufacture of rubber articles, C. A. Burghardt's condensing apparatus, shown in Fig. FIG. 15. 15, is very suitable. It consists of a boiler com- posed of annular pieces a, and surrounded by the vessel c, which contains the cooling water. Between the annular pieces a are fixed steam-tight the cross bottoms b of wire-netting in such a manner that outside the boiler they project into the cooling water whereby they are cooled off. The vapors to ARTICLES FROM SOFT RUBBER. 213 be liquefied are conveyed to the apparatus through the pipe d, or sucked in by means of a suction apparatus through e. In their passage the vapors are condensed on the cooled cross-bottoms b, and pass through / into the collecting vessel g, which is also connected by the pipe h with the boiler, the object of this connection being the condensation of any vapors evolving from g. CHAPTER VII. RUBBER VARNISHES AND LACQUERS. THE properties of rubber, especially its elasticity and chemical indifference, make it particularly suitable for the manufacture of varnishes and lacquers, and there being a constantly increasing demand for these products, waste which could not be utilized in any other manner can be profitably employed for this purpose. The first step required is to transform the rubber into a solution, the solvents which have frequently been referred to being well adapted for the purpose. However, in preparing such solutions, many things have to be observed in order to obtain them of uniform quality, and as they are used for many other purposes besides the preparation of varnishes, it will be of interest briefly to describe the method of preparing them. Preparation of rubber solutions. Rubber solutions for manufacturing purposes are, as a rule, prepared on a large scale, iron vessels hermetically closed being used for the purpose. The rubber is cut up in small pieces, and the solvent should be as free from water as possible. Although the Different varieties of rubber possess, (214) KUBBER VARNISHES AND LACQUERS. 215 as a rule, the same chemical composition, they show considerable difference in their behavior towards solvents. While, for instance, one variety may readily dissolve in oil of turpentine, another does so" with difficulty. It is, therefore, advisable to make a preliminary test with small quantities of rubber and solvent. The most favorable results are obtained by add- ing from 5 to 40 per cent, of highly rectified alcohol to the solvent, the good effect produced thereby being very likely due to the property in alcohol of vigorously absorbing water. If carbon di sulphide or benzene is used as a solvent, special precautions to prevent volatilization have to be employed. The top of the vessel for dissolving the rubber should be provided with a broad rim, upon which a ring of vulcanized rubber is laid, and after the lid of the vessel is placed upon this, it should be held down by placing heavy weights upon it. The vessel is also provided with a stirring apparatus, and in its general arrangement very much resembles that used for bleaching rubber (Fig. 10). The dissolving pow r er of most fluids is increased by heat, and the solution of rubber can be much accelerated by placing the apparatus in a boiler filled with water and heating the latter. With carbon disulphide the temperature should not be above 104 F., with benzene, not above 140 F., and with oil of turpentine or rectified petroleum not over 212 F. But heating should be done only towards the end of the operation. 216 INDIA RUBBER, GUTTA PERCHA, BALATA. Generally 24 to 30 hours are required for effecting complete solution, but as the time may be consider- ably shortened by heating and repeatedly stirring the mass, it is advisable to arrange the stirring apparatus in such a manner that it is connected by a pulley with the engine of the factory and can be constantly kept slowly revolving. When the fluid which is formed after the solvent has acted upon the rubber for a sufficiently long time is examined in a glass, it will be observed that it is never uniform, but that small lumps of more or less swollen rubber float in it. These can never be completely dissolved even by using very large quantities of the solvent. Therefore, to obtain uniform solutions, the mass coming from the apparatus must be subjected to mechanical treatment, and this consists in kneading or squeezing it between rolls. If carbon disulphide or another volatile solvent has been employed, this must be done in a hermetically closed vessel to pre- vent heavy losses of solvent by evaporation. Fig. 16 represents an apparatus which is well adapted for kneading rubber solutions ; it is ar- ranged as follows : Two smooth rolls, a and b, of equal diameter, lie in a box K of wood or iron. The rolls are acted upon by cog-wheels on the outside of the box, in such a manner that they revolve at unequal veloc- ities, and are placed so close together as to leave only a very narrow space between them. The rub- ber solution to be kneaded is poured into the sheet- RUBBER VARNISHES AND LACQUERS. 217 iron vessel G, in the bottom of which is a slit run- ning parallel with the rolls. Smoothing blades S, pressing closely against the rolls, are placed on both sides of them. The solution which is scraped by the blades from the rolls flows into a collecting vessel, and eventually upon a second, third, or fourth pair of rolls. To control the flow of solution upon the rolls FIG. 16. from the vessel G, there is a metallic wedge fitting the slit in the bottom of the vessel G. This wedge can be raised and lowered by a rod projecting above the box, and the discharge of the solution regulated thereby. To be able to observe the flow of solu- tion, a pane of glass is fitted into the side of the box. By repeatedly treating the partly dissolved and partly swollen mass of rubber between the rolls, an entirely homogeneous mass is finally obtained, the 218 INDIA RUBBER," GUTTA PERCHA, BALATA. consistency of which will of course depend on the proportions of rubber and solvent. Very thickly- fluid solutions can be used for casting different articles in hollow moulds, somewhat thinner solu- tions for cementing together pieces of rubber, etc. By reducing the swollen masses of rubber, which have been made homogeneous by passing them through the rolls, with ether, chloroform, oil of turpentine, etc., fluids are obtained which can be used as varnishes without further preparation. In drying, they leave behind a very thin, nearly color- less film of rubber, and such solutions are well adapted for coating copper plates and maps, which can then be cleansed with a moist sponge. For many purposes, rubber solutions are not used by themselves, but are mixed with copal varnish, boiled linseed oil, dammar resin, etc. Varnishes prepared with an addition of resin- varnishes, or lacquers, show a strong lustre, while pure rubber varnishes (that is, solutions of pure rubber alone) possess scarcely any lustre whatever. Below a few receipts for rubber varnishes for different purposes are given : Leather Lacquer. Rubber . . .1 part by weight. Dissolved in oil of tur- pentine . . .8 parts Mixed with fat copal varnish . . .6 Boiled with linseed oil 4 " " RUBBER VARNISHES AND LACQUERS. 219 Varnish for Gilders. Rubber . . .1 part by weight. Dissolved in rectified petroleum . . 8 parts " Mixed with copal var- nish . 4 " " Varnish for Glass. Rubber . . .1 part by weight. Dissolved in chloro- form . . .60 parts " Gum mastic . .10 " " This varnish, which adheres well to glass, may be colored as desired, and with it imitations of flashed glass can be prepared, and glass cemented to glass. It is also well adapted for fastening let- ters of glass or metal upon glass. A varnish which, however, dries somewhat slowly, is prepared by cutting up 1 Ib. of soft rub- ber and allowing it to swell up in J Ib. of ether. The mass is then liquefied by heating in warm water ; it is then mixed with 1 Ib. of warm pale linseed oil, and after some time with 1 Ib. of heated oil of turpentine, and finally filtered. For varnishing morocco, Champagne recommends the following preparation : Allow J Ib. of rubber cut up into small pieces to stand for two days with 1 Ib. of oil of turpentine, then stir vigorously and after adding 1 Ib. more of oil of turpentine, complete solution by heating in the water-bath. Mix 1 J Ibs. 220 INDIA RUBBER, GUTTA PERCHA, BALATA. of the solution with 2 Ibs. of pale copal varnish and 1J Ibs. of boiled linseed oil, and gently heat for some time until a uniform mixture results. A flexible varnish is prepared by melting 1 Ib. of colophon}^ gradually adding J Ib. of rubber cut up in small pieces, stirring until cold, and after adding 1 Ib. of hot linseed oil, completing solution by heating. A water-proof coating for shoes and boots is pre- pared as follows : Soften 1 part of rubber in hot water, cut it up in small pieces with a pair of scissors, and heat gently together with 1J parts of lard and 6 parts of fish-oil, until solution is com- plete. Apply the solution while warm to the leather. It dries in the air to a lustrous coating, and becomes so hard that it does not stick. A solution for repairing rubber shoes is prepared as follows : Pour 12 to 14 parts of carbon disulphide over 2 parts of rubber cut up in small pieces, and let the vessel containing the mass stand in a water bath at 86 F. until solution is effected. The solu- tion is of a paste-like consistency, and to prevent it from hardening too rapidly, reduce it with a solution of rubber and colophony in oil of turpentine, for the preparation of which melt at a moderate heat 1 part of rubber, add to it \ part of colophony, and when both are melted together, add sufficient oil of turpentine. Marine glue. The preparation known by this name is an excellent rubber varnish for protecting wood and metal against the action of water. It RUBBER VARNISHES AND LACQUERS. 221 consists of a solution of 1 part of rubber in 12 parts of rectified petroleum, which is combined by heat- ing and stirring with 6 parts of shellac or asphal- tum. It should be applied at a temperature of from 266 to 284 F. Marine glue for damp walls. It is frequently a very difficult matter to keep the basement walls of houses entirely dry. Generally they absorb so much moisture from the ground that the glue which has been mixed with the paint commences to mould, and the painter's work falls off, or in case the room is papered the wall-paper puffs up arid becomes stained. These evils can be best avoided by using the following marine glue : Parts. Rubber . . . . . 10 Whiting . . . . . 10 Oil of turpentine .... 20 Carbon disulphide ... 10 Colophony ..... 5 Asphaltum 5 These substances are put in. a large bottle, and this is closed as air-tight as possible. It is then put in a moderately warm place and allowed to stand until the soluble substances have become dissolved ; this can be hastened by frequently shaking the bottle. The wall to be dried is first thoroughly cleansed, the glue is then applied with a flat brush, and should be laid on about 8 to 12 inches higher up than the wall appears to be damp. Paper which 222 INDIA RUBBER, GUTTA PERCHA, BALATA. will adhere very -tightly to it is then laid over the glue while it is still sticky. The wall-paper can be immediately pasted upon this paper, and if the glue has been prepared with due care, will never fall off, as the wall will always be dry. Jeffery's marine glue. This consists of rubber 3 parts, undistilled coal tar 36, asphalt 6. The rubber is cut up in small pieces and dissolved in the coal tar, and the asphaltum is then added. The marine glue obtained in this manner is so hard that it cannot be readily melted over an open fire. When it is to be used, it is first softened in a water-bath, and can then be made more liquid over a coal fire without running the risk of scorching it. An excellent transparent cement for glass upon glass is obtained by dissolving 75 parts of rubber and 15 parts of mastic in 60 parts of chloroform. For cementing rubber to metal, a solution of 1 part of shellac in 10 parts of ammonia is used. Hard rubber lacquer. Waste and broken articles occurring in the manufacture of hard rubber can be used for one purpose only, namely, for the prepara- tion of lacquer. The pieces of hard rubber are melted in an iron pot and must be constantly stirred to prevent scorching. The melted mass is poured in a thin stream upon iron plates, where it congeals to a brittle mass resembling asphaltum. The latter is broken into pieces, which are put in a bottle, and rectified petroleum, or, what is still better, benzol is RUBBER VARNISHES AND LACQUERS. 223 poured over them. The quantity of solvent added must be sufficient to produce a fluid which can be easily applied with a brush. The fluid is allowed to stand for a considerable time, during which the foreign substances mixed with the hard rubber, and which are insoluble in petroleum or benzol, settle to the bottom, and the solution is then poured off very carefully. Hard rubber lacquer when applied to wood or metal forms a brownish-yellow to black coating which strongly resists atmospheric influences, and for this reason is especially adapted for varnishing machines erected in the open air. II. GUTTA PERCHA. CHAPTER VIII. RAW MATERIAL. GUTTA-PERCHA,* as regards its natural formation and composition is a plant-product similar to rubber. It is obtained from the milky juice of certain trees, and it is also a hydrocarbon composed of about equal parts of carbon and hydrogen. Historical Review. Gutta-percha was first brought to Europe, in 1866, by the English traveler John Tradescant, who called it " mazer wood." The sample, which he brought home from his travels, was considered a great curiosity, and may be seen at the present day in the Museum Tradescantium, South Lambeth, London. However, no one took the trouble to examine this new product, and still less to apply it to practical use. Even at the commencement of the 19th century but little notice was taken of it. Scientists and manufacturers were occupied with the examination * Latin : gummi plasticum; French and German: gutta- percha. (224) RAW MATERIAL. 225 of rubber, and gutta-percha was at tbat time gener- ally considered as a non-clastic, inferior quality of rubber, which could not compete with the Brazilian and East Indian products. Only its defects were seen, and no one had the remotest idea of those quali- ties which at present make gutta-percha an inval- uable material. In 1832, Dr. William Montgomery, who prac- ticed medicine in Singapore, entered into conversa- tion with a Malay laborer. While talking he observed the handle of a hoe, and he heard with surprise that its substance, however hard it ap- peared to be, could be softened by immersion into hot water, and could thereupon assume and pre- serve any desired shape. The experiment being immediately made, the assertion of the Malay was fully confirmed. On further inquiry, that excellent quality of the substance in question was found to have been long known among the natives of Java, where it was used for manufacturing canes and handles of whips, as well as of various other imple- ments, and especially of knives and daggers. Dr. Montgomery procured a sample of this remarkable substance and on experimenting with it, found that this new gum was in certain respects superior to rubber for surgical instruments, since the latter be- came soon sticky under the influence of the moist warm temperature of the inter-tropical zone. In 1843, he reported his discovery to the Medical Board at Calcutta, and at the same time instructed his friend, Dr. Jose D'Almeida, to communicate his 15 * 226 INDIA RUBBER, GUTTA PERCHA, BALATA. discovery to the Royal Society of Arts, which awarded to Dr. Montgomery its gold medal. For the purpose of experimenting D'Almeida furnished small quantities of the so-called gum to English manufacturers, but these experiments were not encouraging, because the special value of the material was not recognized. However, a portion of the samples reached Paris, and were there util- ized for probes and other surgical instruments, which were formerly made from rubber. In 1845, Lagrenee, returning from a voyage, procured in Singapore quite a considerable quantity of gutta percha, which he presented to the French Minister of Commerce. The latter placed it at the disposal of some manufacturers, and in the fol- lowing year, Alexandre, Cabriot and Duclos ob- tained the first patent for the utilization of gutta percha. From this patent (July 28, 1846) dates the intro- duction of gutta percha and the creation of a new industry. It would lead too far to discuss the various stages through which this industry had to pass before gutta percha was thoroughly understood and finally took the place in the industries which properly belongs to it. It may suffice to say that attempts were successively made to use this new product for all articles formerly made of rubber. However, in fact, all these experiments were con- trary to the characteristic properties of gutta-percha, the greatest difficulty being that it becomes plastic in the heat. Attempts were made to overcome* this RAW MATERIAL. 227 defect by vulcanization, which had been so success- ful with rubber. But sulphur acts upon gutta percha in an entirely different way from rubber, and thus the hopes which had been entertained were of short duration. However, the discovery of the peculiar properties of gutta percha were made just at the proper time, when dynamic electricity com- menced to play an important role. It was found to be an excellent insulating material, and that it remains unaltered in water and especially in salt water, which led to the" idea of using it as an en- veloping material for submarine telegraph cables. The honor of first constructing telegraph lines insulated with gutta percha belongs to Werner Siemens, who, in 1847, built such a line on a Ger- man railroad. Wheatstone, as early as 1837, had the idea of connecting England by telegraph with the Continent, and he considered gutta percha as the most suitable material for use in the construction of submarine cables. However, his idea was first actually carried out by Walter Breit, who, January 10, 1849, laid at Folkestone a submarine cable, two miles long, insulated with gutta percha. In the meantime gutta percha was found to be an excellent material for .sharp moulds such as are required in galvanoplasty, and its resistance to acids led to the fabrication of receivers, funnels and tubes for use in chemical factories, photographic and other labora- tories. Occurrence of Gutta PercJia. Most of the gutta percha plants belong to the nat- 228 INDIA RUBBER, GUTTA PERCH A, BALATA. ural order Sapotacese growing in the Malay Penin- sula. The most important are : 1 . Dichopsis gutta, or Isonandra gutta, or Palaquium gutta. It attains a height of 60 to 80 feet, with a diameter of 2 to 4 feet. The leaves are obovate- oblong and entire, pale-green on the upper side and covered beneath with short reddish-brown shining down. The flowers are arranged in clusters of 3 or 4 in the axis of the leaves. The fruit, about an inch long, is of an ovoid shape, and is eaten by the Malays. The wood is soft, fibrous, spongy, of a pale color, and marked with black lines, these being reservoirs of gutta percha. The gutta as it flows from the tree is of a grayish hue, occasionally with a somewhat roseate tinge. 2. Dichopsis oblongifolium. This variety is found in Borneo and differs chiefly from the preceding in having oblong instead of obovate-oblong leaves. The gutta obtained from this tree is excellent as regards uniformity and durability. When free from bark and wood it is very tough and elastic so that it can be folded together without breaking. When dipped in hot water it can be kneaded and moulded without becoming sticky, and on cooling reassumes its former solidity. Its color varies be- tween red and dark brown. Like all other varieties of gutta percha the juice as it exudes from the tree is milk-white, the brown color being imparted to it by being mixed with particles of wood and bark, which in boiling and purifying the gutta yield to it their coloring matter. RAW MATERIAL. 229 3. Dichopsis calophylla (Benth. and Hook.) ap- pears to be the Mayang Baton mentioned by Selig- mann-Lni. It yields a paler gutta of a more reddish color, inferior in quality and stiffness to Dichopsis oblongifolium. 4. Dichopsis selendit yields a very bard gutta suitable for the manufacture of cables. Mixed with other varieties, it may, however, be also employed for other purposes. 5. Dichopsis Krantziana, is a tree called in Cam- bodia by the natives Thior, and in Cochin-China, Chay. Botanically it resembles Isonandra gutta. The gutta obtained from it is of an inferior quality, and even when mixed with other varieties does not give a product which can be recommended. 6. Dichopsis pustulatum was discovered in Perak, and is now cultivated in Ceylon as a gutta percha tree. 7. Payena Lerii is the only tree belonging to the variety Payena which yields gutta. It was dis- covered by Brau de St. Pol-Lias. It yields a very fair, red gutta. 8. Bassia Parkii is of importance as a gutta percha tree among the Bassiese. 9. Mimusops. The product of this plant is no longer brought into commerce under the name of gutta percha, but as Balata. Under this name it has brought about a special industry which occu- pies about the same position to gutta percha as the latter does towards rubber, and hence a separate chapter will be devoted to it. 230 INDIA RUBBER, GUTTA PERCHA, BALATA. The geographical distribution of the trees pro- ducing gutta percha is very restricted, the limits being about 6 N. and S. latitudes and 100 to 120 E. longitude. Many of the best varieties are found only on the hill slopes at a distance from the sea-coast, each variety forming a separate grove of from 200 to 500 trees, with high forest trees above them. They grow best in a rich light loam with a rocky subsoil. Manner of Obtaining Crude Gutta Percha. The collection of gutta-percha generally takes place directly after the rainy season, as in- the dry season the gutta does not flow so readily, while dur- ing the rains, ague and jungle fever are most pre- valent, and the gutta is liable to be washed away from the felled trees. The methods of extracting the gutta-percha are much the same amongst the Malays, Chinese and Dyaks. The trees are cut down just above the buttresses, and for this purpose a staging about 14 to 16 feet high is erected. The tools used in felling are either " billiongs " or " parangs." A billiong is a kind of axe, with a blade of a chisel-like form, and the tang is secured at right angles to a handle by means of a lashing of rattan or cane. The Chinese sometimes use an axe perfectly wedge- shaped. The parang looks more like a sword bay- onet, and in the hands of a Malay is a box of tools in itself, as with it he can cut up his food, fell a tree, build a house, or defend himself. RAW MATERIAL. 231 When the tree is felled the branches are quickly lopped off to prevent the ascent of the gutta to the leaves. Narrow, strips of bark, about an inch broad and 6 inches apart, are then removed, but not all round the tree, as its underpart in its fall becomes buried in the soft earth, much sap being thus lost. Some natives beat the bark with mallets to accel- erate the flow of milk or gutta. The milk flows slowly and rapidly concretes, and, according to its source, may vary from yellowish white to reddish and even brownish in hue. The gutta as it flows is received in hollow bamboos, doubled up leaves, spathes of palms, pieces of bark, cocoanut shells, or in holes scraped in the ground. According to observations made by Leon Brasse and Seligmann-Lui in the regions of production, gutta-percha is prepared in various ways. Thinner milky juices, like that of Payena, are brought in a liquid state into the hut of the native, while thicker juices, such as those of Dichopsis, become mixed in exuding with particles of wood and concrete still more during transport. The native removes with the hand the coarsest splinters of wood and bark and then throws the mass into a pot of boiling water. The gutta becomes soft so that it can be kneaded and is converted into a compact mass. Good qualities do not stick to the fingers. The mass is worked into strips as thin, and even as pos- sible, whereby the greater portion of the particles of wood come to the surface and can be removed by cold, rubbing or in some other manner. As a rule 232 INDIA RUBBER, GUTIA PERCHA, BALATA. this operation is twice repeated. The gutta is then again softened, kneaded, rolled out in sheets, washed and rubbed and folded into blocks of various sizes and shapes. Gutta percha twice cleansed is, of course, much better than the product which has been but.once manipulated ; yet it is not quite pure, as it still contains a considerable quantity of par- ticles of wood, which, when the gutta-percha is to be used for industrial purposes, have to be removed. In Sumatra the gutta is not purified, but just the reverse, is, as a rule, intentionally adulterated by the addition of quantities of pulverized bark. In the course of all these processes the gutta-percha changes its color. While originally white on exud- ing from the tree, by being boiled it acquires, in consequence of the admixture of bark and wood, a darker hue, which varies in the different varieties. While the gutta of Payena becomes yellowish by the influence of the air, that of DicJwpsis is only colored by the coloring matter it absorbs during boiling. Unmixed gutta-percha, i. e., derived from one and the same variety of plant, is seldom found in commerce. When the collector has found a certain quantity of gutta percha of good quality, but not enough to sell it to advantage, he looks around for a tree from which he can get what is lacking. How- ever, not to lose time in hunting, he attacks the first tree he finds and takes all that is offered until the desired quantity is obtained. On returning to his hut he mixes everything together. This custom is so general that it is impossible to procure from the f uNlVERSn 1 p f RAW MATERIAL native dealers samples of each kind. The most suc- cessful mixture is frequently designated as Balam- ttmbago, even when the juice of Dicliopsis oblongi- foli'um is contained in it. Experience, however, has taught the Malays which kinds go w r ell together and which interfere with each other, and in their own interest they take care not to mix the latter. Regarding the yield of crude product obtained from the different varieties of gutta-percha trees, it would seem that this is largely influenced by geo- graphic and climatic location, the age of the trees, the season of the year when the juice is collected, the mode of felling the trees, manner of gathering the juice, etc. The statements in reference to the yield are at such variance as to leave a doubt of the correctness of any of them. Thus Burke gives the average yield from full-grown trees as 11 ozs. Ser- rulaz states that a gigantic tree felled in Pahang yielded 13J ozs., while Wray gives the product of a Taban merah tree, 100 years old, as 2 Ibs. 5 ozs., and that of a full-grown Taban putch tree as 2 Ibs 11 ozs. Logan, on the other hand, .gives the average yield of a tree, for Johor, as 5J Ibs., and Oxley, for Singapore, as 13J Ibs. No matter which of these statements may be correct, the fact remains that even in the most favorable case the yield of a tree is small, and that with the irrational manner in which the juice is collected, the trees still in exist- ence will become more and more decimated, and that there is danger of a decrease in the exportation and finally of entire exhaustion of the sources. 234 INDIA RUBBER, GUTTA PERCHA, BALATA. The question of how to meet this danger has occu- pied many minds, and finally E. Jungfleisch con- ceived the idea of overcoming it by a more rational mode of harvesting. An examination of specimens of plants led him to the conclusion that gutta is contained in all parts of the gutta-percha tree, not only in the trunk, but also in other organs, and very likely in far greater quantities than the Malays could extract from them. In his report, in 1892, to the Societe d'encouragement, Jung- fleisch states that experiments have shown that there are several solvents with the assistance of which gutta-percha can be extracted from the plant-cells, toluene having proved the most effec- tive. It completely dissolves the three constituents of gutta percha gutta, albane, and fluavile but with the exception of a small quantity of chloro- phyl, very little of the other substances contained in the leaves, bark and wood passes into the solu- tion. The experiments were made : 1. With leaves dried in the air, i. e., leaves ex- posed to oxidation by the air. 2. With leaves dipped while fresh in antiseptic water and then dried. 3. With dried shoots deprived of their leaves. 4. With dried wood, two years old and deprived of its leaves. All these parts yielded a considerable quantity of gutta-percha. The method of extracting the gutta percha by this process is very simple. The pulverized mass, RAW MATERIAL. 235 i. e., leaves, shoots, barks, etc., is heated to aboirt 212 F., and then mixed with a solvent, for in- stance, toluene, the result being a solution, colored green by chlorophyl. Direct evaporation of the solvent is impossible without injury to the product, and hence the toluene is removed by means of steam of at the utmost 212 F. One part of steam carries off 4 parts of toluene, the gutta-percha re- maining behind. For the complete separation of the toluene the steam is allowed to act for some time on the mass kept in motion and at a tempera- ture of 212 F. Besides Jungfleisch and Serrulaz, D. Rigole, Prof. Ramsay and Dr. E. Obach have occupied them- selves with the gaining of gutta percha by extrac- tion, and numerous apparatuses have been con- structed for the purpose, which are described in Dr. Obach's "Cantor Lectures on Gutta Percha." London, 1808. Commercial Gutta Percha. The principal port of shipment of crude gutta percha is Singapore. Before exportation it gener- ally undergoes examination and classification into parcels according to quality. As received in the "godowns" or warehouses, it presents great diversi- ties in condition, shape, size and color from crum- bling, hardly coherent, whitish or greyish " raw " or " getah muntali " fragments, to reddish or brown- ish blocks as hard as wood. Sometimes it is made up into all manner of grotesque shapes of animals, 236 INDIA RUBBER, GUTTA PERCHA, BALATA. and it is nearly always largely adulterated with sago flour, sawdust, clay, stones, etc. The Chinese are great adepts in assorting and classifying gutta, and frequently prepare from different varieties a certain " standard sample," by cutting or chopping the material into thin slices and boiling with water in large shallow iron pans, keeping the contents constantly stirred with poles, and adding good gutta- percha and even cocoanut oil to give a better ap- pearance. When sufficiently boiled the gutta- percha is pressed into large moulds, and is then ready for shipment. This process of reboiling is wholly unnecessary, and in some cases is done only to get rid of stuff which has no right to be called gutta-percha. A brief summary of the best known varieties of gutta percha, including their commercial names, place of origin, form in which they are brought into commerce, appearance, properties, etc., is given below : Pahang. Origin : State of Pahang, east coast of the Malay Peninsula. Form: Generally small pieces. Pear-shaped pieces weigh 1 to 2 Ibs.; rec- tangular oblate pieces, at the utmost 6 Ibs. 6 ozs. Appearance : Yellowish ; seldom red ; mostly play- ing into greenish. Cut surface : White-yellowish ; very seldom yellow-reddish ; compact, seldom fol- iated. Nature and quantity of impurities : Some par- ticles of wood ; 30 per cent. Valuation : This qual- ity works up very well, remains for a long time very nervy, and on cooling rapidly regains its RAW MATERIAL. 237 original hardness. Nature of the thread : Somewhat wrinkly. Sandakan. Origin : In the North Eastern part of Borneo. Form : Loaves in the shape of a parallel- epiped with trapeziform base and boat-shaped elon- gation, weighing 4 Ibs. Appearance: Pale yellow. Cut surface: White-yellowish, very seldom yellow- reddish ; compact, seldom foliated. Nature and quan- tity of impurities : Small quantity of bark ; 22 per cent. Valuation: Like the preceding. Nature of the thread: Smoother than the preceding. Maragula. Origin: Not known. Form: Very flat loaves weighing 2 Ibs. or less. Also flat or four- cornered pressed spindles weighing 6 to 8 Ibs. Appearance: White-gray, with grayer spots. Cut surface : Horny. Nature and quantity of impurities : The mass contains no irregular particles of bark, but regular cut pieces are found which no doubt have been intentionally added ; 16 per cent. Valu- ation : Very hard, rapidly cooling gutta. Nature of the th read : \ V ri n k 1 y . Bagan. Origin: Very likely between Malacca and Singapore. Form : Pear-shaped pieces weigh- ing 4 to 6 Ibs. ; or turnip-shaped pieces weighing 12 to 17 Ibs. Appearance: Wine-red; feels, either cold or warm, like soap. Cut surface: More or less rugged ; numerous holes due to the imperfect cementing together of the separate pieces of which the large pieces are composed. Nature and quantity of impurities : Either none or few particles of bark ; 29 per cent. Valuation : Quite hard, nervy, and 238 INDIA RUBBER, GUTTA PERCHA, BALATA. rapidly cooling gutta. Nature of the thread: Very smooth. Smells of opium ; is difficult to cleanse ; resembles very much balata in its behavior in cleansing and spinning. Banjer-massin. Origin: South Borneo. Form : Clubs about 32 inches long and 3{ to of inches in diameter, rounded off on both ends. Also parallel- epipeds ornamented on both sides with sculptures, a monster upon one side and foliage upon the other. Appearance: Spongy, brown, even blackish. Cut surface: Salmon-red, foliated. Nature and quantity of impurities : Many particles of bark; 45 per cent. Valuation: Very hard, very nervy, rapidly cooling gutta. Nature of the thread : Wrinkly. Kotaringin. Origin: South Borneo. Form: Spindles pointed on both ends, the cross-section of which is square or oblate, and which weigh 2 to 4 Ibs. Also parallelepipeds rounded off and reduced on the ends and weighing to 8 Ibs. Appearance: Paler than the preceding. Cut surface: Salmon- red, foliated. Quantity of impurities: 32 per cent. Valuation: Somewhat less nervy than Banjer-mas- sin. Nature of the thread : Wrinkly. Pekang. Origin: In Pekang on the sea-coast. Form: Loaves 1J to If inches thick and weighing 4 to 11 Ibs. Appearance: Brown-reddish, dark plume-color, mouldy. Cut surface: Wine-red, very homogeneous. Nature and quantity of impurities : 23 per cent. Valuation: Not very hard or nervy; cools with difficulty. Nature of the thread: Smooth. Sarawak. Origin : Northwestern part of Borneo. RAW MATERIAL. 239 Form : The loaves, when dry, are light in propor- tion to their size. Appearance : Spongy loaves ; the surface is warty with earth-brown bark. Cut sur- face : Yellow-reddish with white veins. Nature and quantity of impurities : Many particles of bark ; 50 per cent. Valuation : Very good quality ; very nervy ; cools rapidly. Nature of the thread : Wrinkly. PontianaL Origin : Southwestern portion of Borneo. Form: Blocks weighing 11 to 22 Ibs. Appearance : Very spongy, yellow-reddish, grayer than Sarawak. Cut surface: Like Sarawak, gray or with white veins. Nature and quantity of impur- ities : Many impurities ; 44 per cent. Valuation : Very good gutta. Nature of the thread : Wrinkly. Pedang. Origin: West Sumatra. Form: Flat parallelopipeds weighing about 4 Ibs. each. Each of them bears the stamp of its origin. Also larger loaves weighing up to G6 Ibs. Appearance: Very pronounced yellow-reddish. Cut surface: Like the outside; perceptibly foliated. Nature and quantity of impurities : Many impurities ; 40 per cent. Val- uation : Hard and nervy ; cools rapidly. Nature of the thread : Nervy. This gutta-percha cannot be used unmixed for electrical purposes. Sarapong or Souni. Origin : East Sumatra. Form : Oval loaves running to a point on both ends, and weighing from 1 to 2 Ibs. Appearance : Surface wrinkly, earthy. Cut surface: Homogene- ous, white-yellowish. Nature and quantity of impur- ities : Very pure ; 30 per cent. Valuation : Inferior 240 INDIA RUBBER, GUTTA PERCHA, BALATA. quality ; quite hard but not very nervy ; cools well. Nature of the thread : Very smooth. The term Souni is applied to a series of mixtures prepared by the natives of Sumatra, which contain white and red gutta in varying quantities. Selig- mann-Lui saw the following mixture prepared : Gutta Derriam (Dichopsis oblongifoUum) 2 parts, Sundeck (Payena Lerii) 3 parts, Pontch (Boula- Balam) 1 part. Sarapong is a type of a good mix- ture suitable for telegraph wires. Siak. Origin: East Sumatra. Form: Clubs thicker in the centre and weighing from 4 to 7 Ibs. Appearance: Yellow-reddish. Cut surface: Paler, foliated. Nature and quantity of impurities : Very much bark ; 50 per cent. Valuation : Quite hard but not very nervy ; cools quite well. Rain-re of the thread : Very smooth. Bolungan. Origin : East Borneo. Form : Clubs provided on top with a loop which is formed by folding the thinner portion of the club upon the thicker, and several times twisting this end. The best quality comes in small loaves weighing 4 to 10 Ibs., also larger loaves weighing up to GO Ibs. Ap- pearance : Blackish, almost sooty; knotty. Ont sur- face: White or violet color; foliated. A jnice exudes which, on exposure to the air, immediately hardens upon the knife. Nature and quantity of impurities: Very pure, but adulterated with pieces of bark all of the same shape and very likely ob- tained from the tree producing the gutta. Valua- tion : Hard, nervy ; cools well. Nature of the thread : Wrinkly. RAW MATERIAL. 241 Coti. Origin : East Borneo. Form : Pieces of even size. Rolls 32 inches long and 5| inches in diameter. They are formed of thin leaves rolled up ; the ends have been turned back with the hand and show the imprint of the fingers which have kneaded the gutta. Appearance: Like covered with a net. The meshes of the net are filled with yellow or yellow-reddish particles of wood. Many pieces bear a stamp and are then mostly somewhat reddish. Cut surface : Perceptibly foliated, white-yellowish or grayish, and like Bolungan separates a viscous liquid. The cut surface of the stamped pieces is more reddish. Nature and quantity of impurities : But little bark ; 30 per cent. The stamped pieces contain more bark. Valuation: Hard, quite nervy, cools well. The stamped pieces are of better quality. Nature of tlie thread : Quite smooth. Cotonan. Origin : Unknown. Form : Small, flat loaves weighing 4 to 6J Ibs. Appearance: Surface very smooth. Cut surface: Very white; separates a viscous fluid.. Nature and quantity of impurities: Little or no bark, but much water; 30 per cent. Valuation : Hard, but not nervy ; cools well. Nature of the thread: Very smooth. The separated fluid smells like rotten cheese. Loss in washing, 30 per cent., of which only 2 per cent, is solid constituents. Kclatan. Origin : Northeastern part of the penin- sula Malacca in the northern portion of Pahang. Form: Balls of thread analogous to the African rubber balls and weighing 1 to 2 Ibs. Appearance: In a fresh state rose-color and wax-like ; when older, 16 242 INDIA RUBBER, GUTTA PERCHA, BALATA. chalk-white. Cut surface: Very white, separates a viscous fluid. Quantity of impurities: 30 per cent. Valuation : Very friable ; on the whole not very hard ; does not cool well. Nature of the thread : Very smooth. Under this name two kinds of gutta percha are known. On examining the one kind, it is plainly seen that it is just as it has been collected. This is known as gutta vierge. The second kind consists of two parts, a core of inferior quality coated with a layer of better quality. This variety becomes brittle in a short time. Pahang-white. Origin: Pahang. Form: Balls of a size larger than a head. Appearance : Chalk-white. Cut surf ace : Friable. Quantity of impurities : 40 per cent. Valuation : Quite nervy, viscous ; cools well. Nature of the thread : Very smooth, but difficult to work by itself, as it sticks to the cylinder. The sur- face of this variety frequently consists of a layer of nervy gutta only a few millimeters thick. Smells of fresh cheese. Assahan. Origin : Northeastern part of Sumatra. Form, Appearance and Cut surface: Same as Pahang- white. Quantity of impurities : 20 per cent. Valua- tion: Somewhat inferior in quality to Pahang- white, it being more viscous and does not cool as well. Nature of the thread : Same as Pahang-white. Tringanon. Origin: Northeastern part of the Malay Peninsula on the shores of the Kelatan. Form, Appearance, Cut surface: Same as the pre- ceding. Quantity of impurities : 31 percent. Valu- RAW MATERIAL. 243 ation and Nature of the thread: Same as the pre- ceding. Boida-Balam. Origin: Malacca. Form: Shape- less pieces which must be quickly pressed into blocks as otherwise they crumble to dust. Appear- ance : Chalk-white. Cut surface : Friable. Quantity of impurities : 31 percent. Valuation: A soft gutta without nerve. The pieces stick together even after cooling for several days. To prevent them from forming a mass they must be dusted with talc powder. The tree producing this gutta grows in the marshy regions of the gutta-percha countries. Nearly all varieties of gutta are adulterated with this quality. Notwithstanding its low price, but little of it is used, which is very likely due to the fact that enough of it is contained in the white gutta by the addition of which the working of the good brands is only rendered possible. Statistics. As previously mentioned, Singapore is the principal and almost exclusive market for the ex- port of crude gutta percha. From statements taken from the Straits Settlement Government Gazette and the Blue Books, and from the statistical reports of the British Custom House, Dr. E. Obach calcu- lates the quantity of crude gutta percha brought to Singapore for the years 1885 to 1896, as 542,081 cwts., valued at 3,547,787, which gives an average price of 14 pence per pound. According to the same sources, the export of crude gutta percha from Singapore from 1885 to 1896, inclusive, amounted 244 INDIA RUBBER, GUTTA PERCHA, BALATA. to 619,377 cwts., valued at 4,855,794, which shows that the export during that time was 77,296 cvv 7 ts., valued at 1,308,007 greater than the receipts- Hence this excess must have been taken from stock on hand prior to 1885. According to the quan- tities shipped direct from Singapore, the countries into which the product was imported may be ar- ranged as follows : England .... 470,770 cwts., France .... 54,215 cwts., Germany. . . . 47,151 cwts., United States . . . 37,894 cwts., Asia. . . . . 4,241 cwts., Holland .... 4,202 cwts., Italy .... 895 cwts., Total . . 619,377 cwts. This shows that of the total amount exported from Singapore more than two-thirds went to England. The re-export from England amounted in 1885 to 9,666 cwts., 1886 to 11, 528 cwts., 1887 to 8,824 cwts., 1888 to 8,373 cwts., 1889 to 8, 304 cwts., 1890 to 11,456 cwts., 1891 to 6,408* cwts., 1892 to 7,989 cwts., 1893 to 7,430 cwts., 1894 to 9,975 cwts., 1895 to 12,536 cwts., 1896 to 14,497 cwts. Hence, not quite theee-fourths of the total impor- tation remained in the country for home consump- tion, and in stock. RAW MATERIAL. 245 From the English re-export Germany received about. 48,100 cwts., France received about . 26,000 cwts., Holland received about . 16. 400 cwts., United States received about 11, 500 cwts., Other industrial countries re- ceived about . . 11, 300 cwts., English colonies . . 3,700 cwts. The principal markets for gutta percha in Europe are Liverpool, London, Marseilles, Rotterdam and Hamburg. CHAPTER IX. CHEMICAL AND PHYSICAL PROPERTIES OF GUTTA PERCHA. IN view of the diversity of its origin and the rare occurrence of a pure, unmixed commercial article, i. e., such as is derived from one and the same plant, it is impossible to determine the physical, and still less so the chemical, properties of gutta perch a as absolutely pertinent to all cases. The following statements are based upon observations and experiments made in the best markets, and, generally speaking, may be considered correct. Pure gutta percha is colorless and in thin sections transparent. If a thin slice, about I millimeter thick, is laid upon a white support, it shows, how- ever, a specific coloration between rose color and gray-white. It is tasteless and odorless, and a characteristic pungent odor occasionally evolved by it, is due to decomposition. It is of a cellular struc- ture, but when vigorously stretched it becomes fibrous. In this condition it is very strong in the direction of the pull, but its strength decreases in the crosswise direction, and it breaks readily when pulled that way. At the ordinary temperature separate pieces do not unite, but when their surfaces are slightly heated and pressed together, they com- (246) CHEMICAL AND PHYSICAL PROPERTIES. 247 bine to one piece, the original separate parts of which cannot be restored. At the ordinary temperature gutta percha is com- pact, pliant, very tough, but shows little elasticity. It can without injury be folded, knotted and extended, and is readily coin minuted with pointed or cutting tools. In elasticity it resembles soft leather. Its specific gravity is generally given as from 0.909 to 0.976, but it is actually specifically heavier than water. Thin lamillae of it laid upon water and placed under the receiver of an air pump, sink as soon as the air is exhausted, the numerous small pores having absorbed water. Pa yen, on stretching gutta percha under strong pressure and immediately cutting the strips thus produced into very small pieces under water, found that the greater part of the fragments fell to the bottom of the vessel, some immediately, others after absorbing a certain quantity of water. The pliability of gutta percha increases rapidly at between 76 and 86 F., and at 122 F. it yields readily to slight pressure. At 194 F. it becomes plastic so that it can be kneaded, and brought into any desired shape, which it retains unaltered when brought back to the ordinary temperature. If care- fully heated to 248 F. it melts, and if still further heated it boils up and yields a colorless oil. It is inflammable at a certain temperature, and burns with a bright flame and leaves behind a black residue. Towards cold, gutta percha is less sensitive than 248 INDIA RUBBER, GUTTA PERCHA, BALATA. rubber, it suffering no alteration at 14 F. Cold water has no effect upon it, except, as previously mentioned, that its exterior pores absorb a small quantity of it. Examined in thin sections under the microscope it seems to possess a porous structure. Rubber under these conditions shows little or no change of color, while gutta percha exhibits a beautiful spec- tacle. It appears to be built up of prisms of every variety of hue. Prof. Page states that it resembles more nearly some specimens of ice which he has examined, than anything else. The porous struc- ture ma} 7 be observed by allowing a drop of solution in carbon disulphide to evaporate spontaneously on a glass slide. The solution is soon reduced to a whitish film and the numerous cavities with which it is pierced may be distinctly perceived. These cavities may be made more visible by means of a drop of water; the liquid gradually insinuates itself, the mass appears more opaque and the cavities are seen to be enlarged. Gutta percha is a bad conductor of heat and a worse conductor of electricity. When vigorously rubbed it becomes itself electric, and when rubbed with silk throws out electric- sparks. As regards resistance to the electric current, no other plastic material is even approximately equal to it, and it retains this property unaltered in the ground or in water. Towards most solvents gutta percha is entirely indifferent, Jn cold water it is entirely insoluble, CHEMICAL AND PHYSICAL PROPERTIES. 249 and while it becomes soft in boiling water or in steam, it is thereby not changed in any respect. In cold weak alcohol it is almost insoluble, but in stronger alcohol its solubility increases and the more so the higher the temperature becomes, it losing, in boiling absolute alcohol, 15 to 20 per cent. of its constituents. It is partly soluble in oil of turpentine, olive oil and a few mineral oils, and more soluble in bezene. The best solvents for it are carbon di sulphide and chloroform. According to analysis gutta percha consists of a combination of hydrocarbons, the composition of which resembles very much those of rubber. The oxygen which is found in it very likely belongs to a foreign combination. Gutta percha contains: Carbon . ^^=-=^. 86 - 36 Hydrogen X0sf^P*^\ - 12.15 Oxyo-en f ERSITY) L49 100.00 As far as the chemical composition of gutta percha is concerned, it must not be considered as a single combination, but as a mixture of several bodies which occur in different quantities in differ- ent varieties of it. Two of these combinations can be dissolved by boiling in anhydrous alcohol, and if the solution is allowed to stand quietly for some time, small white grains are separated, the surface of which consists of numerous small crystals, but contain a yellow, amorphous core in the centre. The yellow non-crystalline mass can be more 250 INDIA RUBBER, GUTTA PERCHA, BALATA. easily dissolved in cold alcohol than the crystals, and according to this, gutta percha, by a suitable treatment, can be separated into three parts, one of which (gutta) 'is insoluble in alcohol, the next (albane) is difficult to dissolve, while the third (fluavile) is easily dissolved. Payen, who thoroughly examined gutta percha, found in 100 parts of it : Per cent. Gutta . . . . . 78 to 82 Albane 16 to 14 Fluavile 6 to 4 Pure gutta, which remains after the crude gutta percha has been thoroughly exhausted with alcohol, is a white mass, which, when rolled into thin sheets, is tenacious and ductile at a temperature of from 59 to 86 F., but not very elastic. It becomes soft when heated to 113 F. and assumes a yellowish color ; the higher the temperature the darker and more transparent becomes the mass, and finally be- comes dough-like but without actually melting. It melts when the temperature is raised to 248 F., and commences to decompose at a still higher tempera- ture. Towards solvents its behavior is the same as that of gutta percha. Albane is the crystalline resin which is separated from the solution in boiling alcohol. It melts at from 347 to 356 F. If exposed to a still greater heat it is decomposed and furnishes the same pro- ducts as gutta. ...fluavile. .is a non-crystalline resin of an orange CHEMICAL AND PHYSICAL PROPERTIES. 251 color. It is hard at an ordinary temperature, but becomes soft when taken in the hand, melts between 212 and 230 F., and is decomposed when heated still more, emitting at the same time pungent vapors. Recent investigations have clearly established the relation between gutta, albane and fluavile. Ac- cording to these investigations it may be supposed that the body which is of actual industrial value, namely, the pure gutta, is a hydrocarbon, being composed, according to Baumhauer, of C 20 H 32 . If we compare the formula for the composition of pure rubber (C 6 H 5), established by Williams, with that of gutta, it will be seen that the formula of the latter is equal to four times that of the first, and that, therefore, the two bodies show great similarity in regard to their chemical constitution. Besides gutta (C 20 H 32 ), according to Baumhauer's investigation, two more combinations are found in the crude gutta percha. These are composed of C 2 0^820 and C 20 H 32 2 , and are, therefore, pro- ducts of oxidation of gutta. We might suppose that these products were already present in the fresh milky juice itself, but from the fact that, if gutta percha is stored for any length of time, its properties undergo an essential change, we must conclude that new products of oxidation are con- stantly formed. Mr. Clark carried out a series of experiments upon gutta percha, and below the results as inter- preted by W. A. Miller are"given : 252 INDIA RUBBER, GUTTA PERCHA, BALATA. 500 grains of a thin sheet of gutta percha were exposed for eight months under the following con- ditions : 1. In netting open to the air and light, but ex- cluded from rain. 2. In a bottle open to the air and light, but ex- cluded from rain. 3. In a bottle open to the air, but excluded from light. 4. In fresh water, open to air and light. 5. In fresh water, open to air, but excluded from light. 6. In fresh water, excluded from air and light. 7. In sea water, exposed to air and light. 8. In sea water, excluded from light, but exposed to air. 9. In sea water, excluded from light and air. The specimens 4, 5, G, 7, 8 and 9 were wholly unaltered, with the exception of a slight increase in weight, due to the absorption of water, which they lost again after exposure to the air for one or two hours. The tenacity and structure of the material did not appear to have undergone the slightest change. No. 2, which had been folded up and introduced into a bottle, the mouth of which was open and in- verted, had absorbed 5 per cent, of oxygen, 55 per cent, of the mass being converted into resin. The outer layers, exposed to light, were brittle and resinous, but the inner portions, screened from light by the outer folds, were but little altered in texture or appearance. CHEMICAL AND PHYSICAL PROPERTIES. 253 No. 3 bad experienced little or no change, had in- creased in weight only 0.5 per cent., and yielded to alcohol only 7.4 per cent, of resinous matter. Another sample which had been exposed to the light of day for a period of only two months, had become quite brittle, had increased in weight 3.6 per cent., and yielded 21.5 per cent, of resinous matter to alcohol, while a piece of the same sheet, kept in the dark, had undergone no sensible change. Miller also examined several specimens of cables which had been submerged for periods of time vary- ing from a few weeks to seven years. In, no case ivhere the cable had been completely and continuously submerged, did lie find any sensible deterioration in the quality of the gutta percha. The only perceptible chemical difference in the various specimens was in the quantity of water mechanically retained in each. One of the principal properties of gutta percha is its great chemical indifference. Concentrated alka- line solutions as well as not too concentrated acids, and all saline solutions, do not affect it in the least. It only commences to char when subjected for a long time to the influence of concentrated sulphuric acid ; but fuming sulphuric acid brings about a quicker change, and transforms it into a slimy substance. Even the strongest hydrochloric acid seems to have but little effect upon it ; the only effect observed, after lying for months in the acid, being that it had lost some of its pliability. But cold 254 INDIA RUBBER, GTJTTA PERCHA, BALATA. concentrated nitric acid acts very energetically upon it, and, when boiled, dissolves it completely under the emission of red vapors. Its chemical indifference and great plasticity make this body absolutely invaluable for certain branches of chemical industry. As it is entirely indifferent towards hydrochloric acid, it is used for manufacturing hose for drawing the acid from the vessels containing it, and is even employed for lining boxes in which the acid is to be transported. It is also indifferent towards not too concentrated hydrofluoric acid, and is, therefore, employed for manufacturing vats which are to be used in etching glass, and, also, bottles in which the acid is to be kept. CHAPTER X. TREATMENT OF CRUDE GUTTA PERCH A. PREVIOUS to actual use for manufacturing, crude gutta percha, as brought into commerce, must be subjected to a series of preparatory manipulations, the chief object of which is the removal of foreign constituents, such as sand, earth, wood, bark and other impurities. Various methods are employed for this preparatory work, all of which are quite simple. Before commencing the treatment of the crude material, it is best to more closely examine its con- dition. This is done by taking at random a few pieces from the mass to be tested and catting them up with a knife. If it is found that the impurities consist only of pieces of wood, bark and earth, the gutta percha can be at once brought into the cutting machine. But if it is found to contain stones, it should be subjected to a special operation before it is cut up, since if this precaution is neglected, not only the cutting machine might be ruined, but ac- cidents might also happen. For the purpose of removing stones, the gutta percha is softened in water of about 122 F., and is then rolled out into thin bands. To prevent the rolls from being stopped or injured by the stones, (255) 256 INDIA RUBBER, GUTTA PERCH A, BALATA. they are so arranged that the upper one runs in movable brasses held in place by a lever. In case a stone gets between the rolls, the upper one lifts up and falls down again as soon as the stone has passed through. By forming the gutta percha into bands in the above-described manner every stone can be immedi- ately detected and removed. The bands, while still warm, are folded together so as to form loose blocks of a size corresponding to the cutting machine. The same kind of machine used for cutting up rubber may also be employed for gutta percha, but, as a general rule, machines of special construction are provided for the purpose. Among these the drum slicing machine and the wheel slicing machine deserve special notice. The drum slicing machine consists of two circular disks made to revolve as quickly as possible by a pulley, and are connected with each other by a large number of obliquely-set knives placed upon the sur- face of the cylinder. A vertical cylindrical pipe is placed underneath the cutting machine, and in this is fitted a piston which is pressed upwards by a lever suitably weighted. A cube of gutta percha is placed in the vertical pipe and pushed by the piston against the knives of the revolving disk, and cut into thin slices. The wheel cutting machine resembles a straw cutter. It has a fly-wheel about (>J feet in diam- eter, with the knives fastened to its spokes. The wheel makes from 500 to GOO revolutions per TREATMENT OF CRUDE GUTTA PERCHA. 257 minute. The block of gutta percha is placed upon an inclined plane and is fed to the knives which cut it up in very thin shavings. The shavings thus obtained are placed in cold water to separate the heavy admixtures from the gutta percha which floats on the surface. The gutta percha is then brought into vats filled with hot water, in which it remains until it is soft and the shavings combine to a plastic mass. In this condition the gutta percha is suitable for the manufacture of many articles for technical and other use ; but for special, particularly electrical, purposes, a further very careful treatment for the removal of all traces of water and air bubbles becomes necessary. Gutta percha intended for in- sulating electric cables must form a thoroughly uniform, homogeneous mass, and to attain this object it has to be subjected to a series of other manipulations. For this purpose, it is first brought into the actual washing machine. This consists of an iron box which can be closed by a lid. In the interior of this box is a hollow iron cylinder which contains an iron roll with a star-shaped cross section, Fig. 17. The cylinder is provided with a lid through which the gutta percha is introduced. The box and cylinder are filled with water, which is heated by steam directty introduced. If now the roll in the interior of the cylinder is set in motion by a transmission on the outside of its axis, the gutta percha is forced, in constantly changing form, 17 258 INDIA RUBBER, GUTTA PERCHA, BALATA. through between the walls of the cylinder and the deep indentations of the roll. To still further increase the effect, two nose-like rails are fixed on the bottom of the cylinder which contract the space between the cylinder and roll. The impurities washed from the gutta percha by this process fall to FIG. 17. the bottom of the cylinder and through small apertures reach the bottom of the box, from which they are from time to time removed through small doors. The gutta percha is next brought into the kneading machine, Fig. 18, which closely resembbs the washing machine, except that the exterior box is wanting. In the interior of the machine is a corrugated TREATMENT OF CRUDE GUTTA PERCHA. 259 roll, the corrugations running either parallel with the axis of the roll, or with more or less twist, spirally around it. The operation of kneading is similar to that of washing, the water of course, being omitted. The temperature required is pro- Fig. 18. duced by the introduction of steam in the space between the double walls of the cylinder. There are also kneading machines in which work two horizontal rolls placed one alongside the other, either a corrugated and a smooth roll being used, or two rolls of the same kind, with elliptic disks pushed obliquely over them. The rolls of this latter con- struction are placed so that the disks cross each other, Fig. 19. From the kneading machine the gutta percha is 260 INDIA RUBBER, GUTTA PERCHA, BALATA. brought into a press or strainer, which consists of a cylinder provided on the lower end with several sieves of different-sized meshes, arranged one above the other, or with several perforated bottoms with different-sized holes. The meshes of the sieves or the perforations of the bottoms diminish in size from above to below, so that the uppermost are the widest and the lower ones the narrowest. The whole is terminated by a bottom with perforations FIG. 19. of any desired size. The soft gutta percha is forced through the machine by an accurately-fitting piston. In place of the strainer, ordinary filter presses are also used. By these various operations the gutta percha is thoroughly worked so that any water and air still contained in it are separated, and a homogeneous texture is formed. In order to be able to store the material more conveniently for future use and at "he same time to have it in a more handy form for TREATMENT OF CRUDE GUTTA PERCHA. 261 working, it is, after coming from the kneading machine or press, rolled into thinner or thicker sheets. The machine used for this purpose, Fig. 20, consists of two rolls with very smooth surfaces placed either vertically or obliquely one above the other, and in general corresponds to the calender employed in working rubber. The mass is intro- duced from the front of the apparatus, and on leav- ing it on the back, is taken and carried along by an endless cloth. As in most cases quite definite demands regarding FIG. 20. density, elasticity, electric and other qualities are made on the finished products, and these qualities are seldom or never found in the required degree and proportion in a given kind of raw material, the manufacturer must endeavor to produce them by mixing different varieties. Study and experiments have led to good results in this respect, but, as with rubber, the knowledge thus acquired is kept secret by the various factories. Gutta percha is seldom mixed with foreign con- 262 INDIA RUBBER, GUTTA PERCHA, BALATA. stituents, and in factories particular about quality, it is never done, because by all such admixtures the quality is impaired, which cannot be justified by an eventual cheapening of the price. For incorporating the admixtures, the same machines as for kneading are employed. Like rubber, gutta percha suffers considerable loss by washing and kneading, the percentage varying very much according to origin, quality and other conditions. The best varieties lose as a rule 15 to 20 per cent, in weight, medium qualities, 20 to 25 per cent., and inferior ones, even as much as 50 per cent. CHAPTER XL INDUSTRIAL APPLICATION OK GUTTA PERCHA. THE further working of the cleansed gutta percha, i. e., the preparation of the various articles for which it is employed, is similar to the manufacture of articles from non-vulcanized, mixed and rolled rub- ber sheets. Generally speaking, the manufacture is more simple, because gutta percha is even more plastic and moldable than rubber, and the seams can be readily cemented together. In many cases, gutta percha replaces leather, and for some purposes it is preferable to it. It is espe- cially useful for articles exposed to moisture, damp cold and acids, and for that reason is employed in the form of hose for conducting cold water, beer, vinegar, wine and acids ; for belts running in wet places ; for buckets, ladles, shovels, bottles, siphons, funnels and spigots in chemical factories. It is largely used in galvanoplast}^ for the preparation of moulds and matrices. It is also employed for sur- gical purposes. When perfectly pure it serves for filling hollow teeth and for the manufacture of plates for artificial sets of teeth, and rolled out to the thick- ness of paper for different surgical bandages and com- presses. In the form of very thin taffeta it is used for sweat bands in hats and caps. An important (263) 264 INDIA RUBBER, GUTTA PERCHA, BALATA. application of gutta perch a is its use for coating quick -matches so that they can be carried through water without injury to the priming composition. However, the most important use of gutta percha is as insulating material for electrical wires, especially for submarine and underground cables. Articles are moulded from gutta percha by work- ing it by hand, whilst in a soft and plastic state, into the required form. It needs very careful, though not skilled, labor. To prevent it sticking to the hands or fingers, they should be wetted with water containing a little soap, taking care to remove all traces of moisture when jointing is required. It is kept soft in water heated by steam. Picture frames and similar articles are made in metallic moulds. Gutta percha hose. Special machines are used for manufacturing gutta percha hose. In their con- struction they closely resemble presses used for manufacturing drain pipes from clay, and may be described as follows : A pipe, which determines the outer diameter of the hose to be manufactured, is fitted in the centre of the bottom of a strong iron cylinder. A round core having a diameter equal to the interior diam- eter of the hose sticks in this pipe. When the cylinder has been filled with the material, a strongly wrought disk, which acts as a piston, is placed in it and pressed slowly forward, but with great force, by a rack and pinion. To obtain long and perfect hose, great care must be INDUSTRIAL APPLICATION. 265 observed in charging the cylinder with the gntta percha softened by heat, it being absolutely neces- sary that the entire space be filled without the occurrence of air bubbles. To attain this object the work is done as follows . The gutta percha is divided into small balls about the size of a fist and heated ; as soon as the mass has become sufficiently soft the balls are placed in the cylinder, two men being required for this work. While one workman throws the heated balls into the cylinder, the second stamps them with a flat pestle into a homogenous mass. This labor is con- tinued until the cylinder is filled up so far as to just leave room enough for putting the piston into position. After completing these operations, steam is ad- mitted into the steam-jacket to heat the contents of the cylinder, which may have cooled off somewhat while putting them into the cylinder, and the heat is maintained until the mass is entirely soft. The actual work is commenced when a small test proves that the gutta percha can be worked without difficulty. The hose upon leaving the machine has a consis- tency not much greater than flour dough, and must be cooled off as rapidly as possible to an ordinary temperature in order that the gutta percha may harden. Most of the factories pass the hose, upon its leav- ing the apparatus, through a narrow box, from 15 to 25 feet long, supplied with running cold water. 266 INDIA RUBBER, GUTTA PERCHA, BALATA. Practical results have proved this length to be sufficient to cool off the hose so that it will retain its shape. If hose is to be manufactured of such a length that one charge of the cylinder does not furnish sufficient material, the action of the piston may be stopped when the material in the cylinder is nearly exhausted, and the latter filled anew. The mass is then heated to the necessary degree and the labor continued. Hose more than 975 feet long has been manufactured in this manner. Only very recently, machines have been con- structed which permit the manufacture of hose of any desired length. From the manner in which they work, they may be designated as hose-forging machines. A section of hose of a certain diameter and sev- eral metres long is prepared with the previously- described apparatus. A solid core of a suitable length is inserted in this section, and both are placed in a press, the lower half of which consists of a semi-cylindrical piece of metal corresponding with the outer diameter of the hose. The upper half of the press supports a piece of the same form as the lower, so that both together form a cylinder having a diameter equal to the outer diameter of the hose. The two halves of the cylinder are hollow and can quickly be heated by super-heated steam or hot air to the temperature at which rubber is vulcanized. When the section of hose has been sufficiently INDUSTRIAL APPLICATION. 267 heated, the cylinder is opened, the core withdrawn, and a new section of hose pressed out from the first apparatus, which is then treated in the same man- ner. As the heating process always requires con- siderable time, the press cylinder may be refilled in the meanwhile, and, it will be readily understood, that hose of any desired length can be manufactured in this manner. By a slight modification, the press used for the manufacture of hose may also be employed for pre- paring solid articles of gutta percha. For this purpose, the front of the cylinder is pro- vided with a pipe to which is fitted the open end of a metal mould, the hollow part of which corresponds with the form the article is to have. The mould must consist of several pieces, so that it can be taken apart and the contents removed, and, besides, must be provided with an opening through which the air contained in it can escape. In order to form articles in this manner, the mould is heated to from 86 to 104 F., and then fastened to the pipe, and the softened mass of gutta percha is forced by a strong pressure of the piston through the pipe into the mould, this being contin- ued until the mass makes its appearance through the air-hole. The mould is then removed and allowed to stand until the gutta percha contained in it is cooled off and hard. It is then taken apart and the small cylinder, which has been formed by the mass passing into the air-hole, cut off. Gutta percha threads. Gutta percha being con- 268 INDIA RUBBER, GUTTA PERCHA, BALATA. verted into a very plastic mass when heated, threads of any desired dimensions can be readily prepared from it, rolls as well as presses being used for the purpose. For pressing threads an apparatus closely resem- bling the one used for round rubber threads is em- ployed, but the cylinder into which the gutta percha, previously heated to 212 F., is brought must be surrounded by a steam jacket to maintain this temperature in the cylinder. To prevent the operation from being interrupted and to make it possible to obtain the gutta percha in the form of coherent threads from the narrow tubes, great care must be had in filling the cylinder so that the mass is compact and contains no spaces filled with air, as this would cause the thread to break. The simplest way of avoiding this is to bring the softened gutta percha into a cylinder of the same diameter as the press-cylinder. The mass is solidly pressed into this, and the cylinder of gutta percha thus formed, is then transferred to the press- cylinder. The other parts of the apparatus are arranged in the same manner as in the one used for manufac- turing rubber threads. A number of endless cloths are also used, over which the threads are carried, so that they may cool off and harden, but they need not be as long as those used in the manufac- ture of rubber threads. The best plan for cooling them off quickly is to use a powerful ventilator, throwing out a strong current of cold air. Dusting INDUSTRIAL APPLICATION. 269 with powdered talc is superfluous, as gutta percha loses all stickiness when cooled off to a certain degree. It is best to wind the finished threads upon rollers of considerable diameter, as, when this is done, it is, easier to stretch them straight again in case this becomes necessary. For manufacturing threads by rolling, the gutta percha must first be converted into a band some- what thicker than the diameter of the threads which are to be cut. The rolls used for this purpose are so constructed that half cylinders are cut in each, and the grooves, formed in this manner, stand so close together that their edges touch each other and form cutting edges. The rolls are placed over each other in such a way that two grooves fit exactly together and form a circular groove. The band to be cut into threads is heated to 212 F. immediately before it is passed through between the rolls, and is carried to them over a plate of polished steel. The threads are then cooled off in the same manner as has been described. By using suitably cut rolls elliptic, as well as polygonal, threads can be prepared in this manner. The principal point in arranging the rolls is to see that the grooves in the two rolls fit exactly together, as the threads, if this is not the case, will not acquire the desired form. Coating wires with gutta percha. Of all the indus- trial applications of gutta percha, none is of greater importance than the coating of wires with it, as on 270 INDIA RUBBER, GUTTA PERCHA, BALATA. this depends the establishment of submarine tele- graph lines, there being no other body suitable for this purpose which is such a non-conductor of electricity. Many comparative experiments have proved that a wire becomes insulatec} by simply allowing a coat of an ordinary gutta perch a solu- tion to dry upon it. As the coating not only secures complete insulation, but also protects the w r ire against the action of sea water, it may be said without exaggeration, that if gutta percha and its properties had not been known, submarine telegraph lines would perhaps never have been successful. Insulation of telegraph wires by coatings of gutta percha demands attention to two very important conditions : The wire must lie exactly in the centre of the cable or cylinder, and the covering must be perfectly continuous, as the smallest crack would allow the sea-water to enter, and eventually destroy the insulation. As the manufacture of telegraph cables is a special and limited branch of the industry, requir- ing large plants, it has been thought best not to enter very fully into the discussion of the subject, but confine ourselves to the description of the pro- cess of coating wire with gutta percha, large quan- tities of such wire being used in the manufacture of electric and magnetic machines. The apparatus used for the purpose consists of a cylinder containing the gutta percha which has been softened by heat and is pressed forward by a piston. INDUSTRIAL APPLICATION. 271 The soft mass passes out of an opening which determines the thickness of the gutta percha cylin- der. Below this opening is a die of metal, with a hole just wide enough to allow the wire to be coated to pass through without much friction. When the piston which acts upon the softened material presses forward, a cylinder of gutta percha is pressed out of the respective opening, and this, on account of the strong friction, carries the wire with it and incloses it entirely. As the material must be heated so far that it can be pressed out of the small opening without the use of too much power, provision must also be made for sufficiently cooling the mass off before it is wound upon a drum. All that is necessary in this case, is to carry the wire through a channel 10 to 15 feet long, which is kept constantly filled with water, and then to wind it upon a large drum in such a manner that the separate windings lie alongside each other. The accompanying illustration (Fig. 21) shows such an apparatus of the most simple construction. C is a cylinder containing the softened gutta percha ; .D is the piston by which it is pressed forward ; B is a metal cylinder in the bore of which the wire sits. This is exactly opposite to the opening, 0, through which the gutta percha is pressed. The wire which is to be covered with it is wound loosely upon a drum, and is drawn forward in consequence of the high pressure which the compressed material exerts upon it. 272 INDIA RUBBER, GUTTA PERCHA, BALATA. If several wires coated with it are to be formed into one cable, several such dies of metal in which the wires sit are fastened to the cylinder from which the gutta percha is pressed. The wires which are to be formed into one cable are passed through a cylinder while they are still warm, so that their coatings adhere to each other. The diameter of the FIG. 21. cylinder should be such that the wires, in passing- through it, are gently pressed against each other. But a simple coating with gutta percha does not suffice for cables which are to be immersed in water or to be laid underground. In such a case it serves only for insulating the wire. The cable which has been formed by joining the insulated wires together is generally covered with Manila hemp. A layer of gutta percha is applied to this and the operation repeated several times. To protect the cable from being gnawed by ani- mals, it is covered with galvanized iron wire, which INDUSTRIAL APPLICATION. 273 also receives a coat of gutta percha to protect it against rust. Large cables are generally prepared in such a manner that six copper wires coated with gutta percha lie around a centre wire, which is also coated, the seven wires together with their coatings forming a cylinder having a diameter of from 0.31 to 0.39 inch. However, long submarine cables must be still further secured against breaking, and for this pur- pose are covered with suitable material Manila hemp, galvanized iron wire, etc. until they have a diameter of 1 J to 1J inches. Fig. 22 shows a machine for insulating electric wire and cables, manufactured by John Royle & Sons, Paterson, N. J. In operation, the wire or cable enters the machine at the back and, passing through the bore of the thrust-bearing, enters the stock worm, which is bored through, the opening terminating at the forward end of the worm at a point precisely opposite to a corresponding opening in the bridge holding the guider. The guider is of the customary form, and conducts the wire to the die in the usual manner. The guider, when once set ready for operation, is fixed centrally to the axis of the machine, and cannot be turned or moved in any direction, all adjustments being made with the die, which is of compound form, consisting of a secondary holder and a die of the usual form, the secondary holder being threaded so as to screw into a die-holder 'slightly altered from the regular pattern. This arrangement permits of the die being 18 274 INDIA RUBBER, GUTTA PERCHA, BALATA. adjusted both sideways and lengthwise ; sideways, by means of set-screws bearing on the circumfer- ence of the die-holder ; and lengthwise by means of the secondary holder, which, by reason of its FIG. 22. threaded stem, can be run backward and forward at will. This method of adjustment will be found, in practice, extremely effective. It is simple and easy of operation, the adjusting movements being- directed and depending merely on one piece, not on a combination of movements as heretofore. INDUSTRIAL APPLICATION. 275 In straight-delivery machines, it is important that cables, in passing through, be prevented from coining into contact with the stock-worm, the rotary movement of which might have a tendency to loosen the strands. To prevent any trouble of this sort, the bore of the stock- worm is lined with a fixed steel tube, which passes through the entire length of the thrust-bearing and cylinder and ter- minates at the guider. This arrangement not only prevents the movement of the stock-worm from being communicated to the cable, but also effect- ually protects it from contact with the insulating compound before it reaches the die. Owing to the nature of the compounds used, in- sulating work is extremely severe, subjecting the machine to heavy strains, the back-thrust being, at times, particularly strong. To provide for all con- tingencies, a thrust-bearing has been designed entirely unique in its application to machines of this character and possessing features which fit it pecu- liarly to this class of work. It consists of a series of parallel grooves, extending from the termination of the stock-worm to the driving gears, into which is fitted a corresponding series of rings, which surround the shank of the stock-worm. The stock-worm ex- tends back beyond the cylinder, where it is keyed into the inner portion of this bearing, which, in turn, extends back beyond the driving gear, where it terminates in a bonnet which covers the end of the bearing, and, passing forward over the hub of the driving gear, serves as a medium for 276 INDIA RUBBER, GUTTA PERCH A, BALATA. ting power from the driving gear, through the thrust-bearing, to the stock-worm. Owing to its massiveness there is no danger of this bearing giv- ing way under any pressure that may be brought to bear on it in actual service; and, to prevent heat- ing, carefully selected anti-friction metals are used on the bearing surfaces and ample means provided for such lubrication as may be necessary. Vulcanization of gutta percha. As has been pre- viously mentioned, attempts have been made to mix gutta percha with sulphur and subject it to the same processes by which vulcanization is brought about in rubber. However, these attempts resulted in complete failure, the good and characteristic quali- ties of gutta percha being destroyed by this process, without imparting to it new properties which would render it suitable for any known purpose. For the sake of completeness, a few of the processes recom- mended for vulcanizing gutta percha are here given. A much smaller quantity of sulphur is required for this purpose than for rubber, since the use of an excess of it would result in a brittle product. How- ever, pure sulphur alone is seldom used, preference being given to sulphur in connection with metallic sulphides, or to chloride of sulphur. The following mixture has been recommended : Gutta percha . . 48 parts by weight. Sulphur . .1 part " Sulphide of antimony 6 parts " INDUSTKIAL APPLICATION. 277 The substances are mixed in a manner similar to that which has been described for preparing vul- canized rubber. The gutta percha is vulcanized at a temperature of from 257 to 302 F. The process of vulcanizing gutta percha with chloride of sulphur is as follows : The cleansed gutta percha is cut up into shreds and dissolved in carbon disulphide so as to form a stiff solution of about the consistency of syrup. To this solution 2 to 15 per cent, of chloride of sulphur is added, ac- cording to the required extent of vulcanizing, 10 per cent, rendering the gutta percha hard and horny, and it does not become soft even if exposed to a temperature of 212 F. The hardness increases in proportion to the quantity of chloride of sulphur used. Sheets are vulcanized by repeated dipping. For coating articles with vulcanized gutta percha a stiff solution in carbon disulphide is used. The articles are brushed over with the solution and, w r hen dry on the surface, are plunged into a solution con- taining 5 to 10 per cent, of chloride of sulphur to 100 parts of carbon disulphide. CHAPTER XII. BLEACHING OF GUTTA PERCHA. GUTTA PERCHA COMPOUNDS. GUTTA PERCHA can be thoroughly bleached with- out suffering thereby a chemical change, as is the case with rubber; and its great indifference towards chemical agents, and the fact that by bleaching it loses none of its physical and chemical properties, make itr an invaluable material in dentistry, and the more so as a color can be given to it which so closely resembles that of the human gums as to defy detection. As bleaching agents, animal charcoal or chloro- form may be used. If the latter is employed, the commercial gutta percha is cut up into small pieces, and twenty times the quantity of chloroform is poured over them. When solution is complete, which will be the case in about three or four days, about half a pint of water is added. The vessel containing the solution is then thoroughly shaken and allowed to stand quietly until the contents have become separated into two distinct layers, the lower one of which consists of a solution of pure gutta percha, and the upper one of the water and the foreign substances which had been mixed with the gutta percha. The clear solution is then draw off by means of a (278) BLEACHING OF GUTTA PERCHA. 279 siphon into a porcelain basin. This is placed in a copper still and surrounded with water. The still is then closed and heated, and the chloroform dis- tilled off. The purified gutta percha remains in the porce- lain basin in the form of a vesicular mass, which can be formed into plates and small sticks by soften- ing it in hot water and by mechanical treatment. AVhile a purified article is obtained in this manner, it is not entirely decolorized, as it always shows a weak yellowish or brownish color. An entirely decolorized, pure white product may be obtained as follows : Purified gutta percha is dissolved in twenty times the quantity of carbon disulphide. The solution is clarified by allowing it to stand quietly, and is then filtered through finely powdered animal charcoal. But on account of the great volatility of the solvent, it is necessary to use a suitable apparatus for filtering. An apparatus of this kind, of simple construction, and performing excellent service, is shown in the accompanying illustration (Fig. 23). It consists of a large bottle, F, either of glass or tin. This is hermetically closed by a cork with two holes. The neck of the glass funnel, T, the upper rim of which is ground smooth, is placed in one of the holes, and a glass tube, r, bent at a right angle, is fitted into the second hole. A thick wooden lid, with a ring of rubber on the lower side, is placed upon the funnel, thus closing it air-tight. In the centre of the lid is fitted a glass tube, r', also bent at a right 280 INDIA RUBBER, GUTTA PERCHA, BALATA. angle, which is connected with the tube r by a rubber hose, /. The funnel, the neck of which' is closed by a stopper of cotton, is filled about two-thirds full with animal charcoal. The solution to be filtered is poured upon this, the lid is placed in position, and must be removed only for the purpose of pouring more solution into the funnel. The air in the bot- tle F is displaced by the solution dropping into it, and escapes through r, k, and r' into the funnel T, where it absorbs the vapor of the solution, but ab- sorbs nothing more after it is once saturated. While evaporation goes on constantly when an open funnel is used, it is entirely checked by using this appara- tus. To obtain the last remnant of the solution re- tained by the animal charcoal, a quantity of carbon BLEACHING OF GUTTA PERCHA. 281 disulphide, about f inch deep, is poured upon the animal charcoal, which will remove all the solution from it. The solution filtered through animal charcoal is almost colorless, and after the evaporation of the carbon disulphide an entirely white mass is obtained which can be colored with the most delicate color- ing matter. To remove the last traces of the sol- vent the mass is heated for some time at 212 F. Solutions of gutta percha bleached in this man- ner are entirely colorless, and when spread upon glass plates furnish a coating resembling a film of collodion, but have the advantage of possessing greater solidity and tenacity. As the preparation of bleached gutta percha is rather complicated, it is scarcely employed for any other but dental pur- poses, although an excellent use could be made of it for ivory compositions, though at present such masses can be prepared more cheaply with the assistance of celluloid. CatteWs bleache'd gutta percha is made by dissolving cleansed gutta percha in solvents requiring heat, as coal-tar naphtha and its rectified products, turpen- tine, and rosin-spirit, or solvents requiring no heat- ing, as chloroform or carbon disulphide. In using the first class of solvents, 1 02. of alcohol, holding in solution 30 drops of glycerine to the gallon, is agitated in a closed vessel, together withh the sol- vent and gutta percha, for an hour or more, until sufficiently defecated or decolorized, when it is mixed with a little alcohol and glycerine, to precip- 282 INDIA RUBBER, GUTTA PERCHA, BALATA. itate the gutta percha. The solvent is recovered by distillation. The alcohol or similar agent removes the oxidized portions of the gutta percha, resins, etc., and leaves the pure gutta percha colorless. The product thus obtained can be mixed with coloring pigments for the production of useful or ornamental objects. Oxide of zinc, vermilion, and similar compounds can be used, but not compounds or oxides which represent a saturated or high de- gree of oxidation. Gutta percha by strong oxida- tion gives rise to formic acid. Gutta percha compounds. Gutta percha, similar to rubber, possesses the capacity of combining with a variety of substances and on account of its soften- ing when exposed to heat, the preparation of such compounds presents little difficulty. By choosing suitable substances, compounds resembling leather, wood, whalebone, horn, and even stone can be ob- tained. Compounds of rubber and gutta percha are largely used in galvanoplasty for the production of over- lapping moulds of one piece. By itself, gutta percha is an excellent material for taking impressions of coins, medals, etc., it being only necessary to heat a sheet of it until soft, place the coin or medal upon it and subject the whole to strong pressure, leaving it in the press until cold. The gutta percha sheet then shows the negative picture of the coin or medal in its finest details, and such moulds have the ad- vantage over those of plaster of Paris that they can be repeatedly used for making copies. BLEACHING OF GUTTA PERCHA. 283 However, for over-lapping matrices or moulds a mixture of rubber and gutta percha has to be used, as besides plasticity when heated, they must possess a high degree of elasticity so that when pulled from the copied object, the mould assumes the same shape as when upon the object. The proportion of rubber and gutta percha best adapted for this purpose can only be ascertained by special experiments. A more elastic (richer in rub- ber) mixture must be used for deeply-cut models, which are to be copied (high reliefs) than is necessary for copying a less projecting article (low relief). The best plan for mixing rubber and gutta percha into a homogeneous mass is to pass sheets of them through between heated rolls revolving at unequal velocities, to cut up or fold up the sheet thus formed, to again pass this through between the rolls, and to repeat this operation until an entirely homo- geneous mass has been formed. Gutta percha and rubber compound for machine belts. Compounds of rubber and gutta percha in suitable proportions combine great tenacity and solidity with a certain degree of elasticity, and can therefore be advantageously used for the manufac- ture of machine belts. Although such belts are rather expensive, they are cheaper in the end, as they are almost indestructible, and besides can be readily repaired. A compound very suitable for this purpose consists of: 284 INDIA RUBBER, GUTTA PERCHA, BALATA. Parts by weight. Gutta percha . . . . 70 to 75 Rubber 30 to 25 Sulphide of antimony . . 5 to 4 Sulphur . . . . 2 to 1 To obtain as intimate a mixture as possible, it is advisable to weigh the rubber and gutta percha in the form of shavings, to mix them thoroughly to- gether and form bands in the manner already described. These bands should be rolled until they are entirely homogeneous, the sulphur and sulphide of antimony being incorporated with them at the same time. The mass, when finished, is formed into a block, and this is passed through between the rolls at a rather low temperature, and is gradually changed into a band corresponding in width with that of the belt to be manufactured. When the thickness of this band nearly approaches that which the belt is to have, the temperature is lowered so much that the band can be forced through between the rolls only at the expense of great power, to make the mass as compact as possible. The edges of the belt are then trimmed, and it is covered on one side with a linen or cotton cloth, and wrapped loosely round a wooden roller in such a manner that the cloth forms a layer sepa- rating the windings of the belt from each other, since if this were neglected the mass \vould fuse together during the heating process. It is then brought into the heater, and the temperature, BLEACHING OF GUTTA PERCHA. 285 especially for thick belts, must be raised to 320 F. When removed from the heater, it is taken from the wooden roller, smoothed, and polished by being passed through between the rolls of a calender. Hard -gutta percha compounds. Various admix- tures are used for this purpose, they being nearly the same as mentioned for rubber, including earths, oxides and finely pulverized minerals. While the object of adding some of the ingredients is to give weight or color to the mass, many have no other use except economy in making the necessary bulk.. Whiting, white pipe-clay, magnesia, oxide of zinc, washed barytes or artificially prepared sulphate of baryta are used for white, or rather yellowish colored articles. If they are to be of light weight, it is advisable to use magnesia ; for heavy objects, sulphate of baryta is the best. On account of the brown color of unbleached gutta percha, the compound prepared with white materials will not show an entirely white, but always a more or less yellowish-brown color. If it is desired to obtain entirely white compounds, bleached gutta percha has to be used. Ferric oxide (colcothar) can be used as a com- ponent for reddish-brown compositions; powdered pyrolusite for dark-brown masses ; and black com- pounds may be prepared by incorporating bone- black, etc., with the gutta percha, The total weight of the added ingredients may be greater than that of the original gutta percha, without destroying its plastic property, or prevent- 286 INDIA RUBBER, GUTTA PERCHA, BALATA. ing its being moulded into any desired shape. But such compounds will always show some degree of brittleness, and for this reason their use is limited to such articles as are not to be exposed to shocks, as door handles, escutcheons, ornaments for frames, etc. For articles exposed to shocks, the foreign admix- tures must not amount to more than from 25 to 30 per cent, of the weight of the gutta percha, and from such masses may be manufactured many of the utensils for daily use which were formerly con- structed of leather, tin or wood. To hide the peculiar and not agreeable odor of gutta percha, sweet smelling substances should be mixed with it ; essential oils having frequently been used for this purpose. While these completely dis- guise the odor of gutta percha, they possess the dis- advantage of gradually volatilizing. It is, therefore, advisable to choose substances which will retain their perfume for a long time ; benzoin, tonka beans, and orris root can be recommended. Of benzoin, 4 per cent, of the weight of the mass is sufficient to make the odor an agreeable one ; of tonka beans J per cent, is more than sufficient ; if orris root (the root of Iris florentinst) is used, about 10 per cent, will be required, as its perfume is not very strong. Fine shavings of sandal wood or of American juniper (Juniperus virginiana) may be used instead of orris root. Compounds of gutta percha and wood. For many years, admixtures of finely pul\ 7 erized cocoa-nut shells have been used in gutta percha compounds, BLEACHING OF UUTTA PERCHA. 287 giving to them the properties of wood. The shells are powdered in stamp mills, and the resulting powder is sifted and incorporated with the gutta percha in the usual manner. But powdered wood and sawdust of hard woods can also be used for this purpose. The sawdust is ground and sifted so as to form fine flour. It is, however, absolutely necessary to thoroughly dry the powdered wood before mixing it with the gutta percha, and it may be further recommended to coat the plates, made from such compositions, with a gutta percha varnish. Compounds of gutta percha and wood can, like wood, be worked by means of the saw and turning lathe, and can be very advantageously used for covering wooden articles. But for the wood and composition to adhere tightly to each other it be- comes necessary to frequently saturate the first with linseed oil, before the compound is laid on, to pre- vent it from absorbing atmospheric moisture. If this precaution is neglected and the wood should become damp, the compound would fall off in con- ' sequence of the expansion of the wood. By coating two boards saturated with linseed oil with a gutta percha and wood compound, plac- ing them cross grained upon each other and heating sufficiently to soften the gutta percha, and then subjecting them to a heavy pressure until cold, a tablet of extraordinary tenacity and resistance, exceeding those of the hardest woods, will be formed. 288 INDIA RUBBER, GUTTA PERCH A, BALATA. SoreVs gutta percha compounds. The substitutes for rubber and gutta percha which were introduced by Sorel, must actually be considered as gutta percha compounds, the gutta percha being mixed with pitch, rosin, lime, and potter's clay. The best of Sorel's compounds consists of: Parts. Rosin 2 Pitch or asphaltum .... 2 Rosin-oil ...... 8 Slacked lime 6 Water . . . . . 3 Potter's clay . . . .10 Gutta percha . . . . .12 The purpose of the rosin-oil in this composition is evidently to dissolve the pitch and rosin, and the admixture of lime is very likely for the purpose of effecting a combination between the acids of the rosin and the lime. The potter's clay is introduced into the composition as an indifferent substance to increase the weight of the mass, and can, therefore, be replaced by other indifferent substances (chalk, magnesia, colcothar, etc.), or can be entirely left out. In the latter case a compound is obtained which, in regard to its properties, approaches that of pure gutta percha. The manner of preparing the composition is as follows: The rosin, pitch, and rosin-oil are stirred together in a boiler until complete solution has been accomplished, which can be accelerated by heating BLEACHING OF GUTTA PERCH A. 289 the substances. The lime and water mixed together to a paste are then added, and finally the gutta perch a and potter's clay, but the latter only when the gutta percha has become fluid. More water is added to the mass, and it is heated to the boiling point of water, 212 F., and then taken from the boiler. Even if the work is carried on with the greatest care, it will be impossible to obtain in this manner an entirely homogeneous composition. To do this, it is necessary to pass the mass several times through between rolls. 5 per cent, of stearic acid or wax should be added to the composition for the purpose of making it entirely water proof. Sorel varies his mixture to suit different purposes and claims that they can be substituted for pure gutta percha ; but his compositions have not the great tenacity of the pure material, nor its indiffer- ence to chemical action, and cannot be advan- tageously used for articles liable to exposure to chemical agents. The following are some of Sorel's receipts for manufacturing gutta percha compounds : I. II. III. Parts. Parts. Parts. Pitch . . .8 12 'Rosin-oil ... 4 Coal tar ... 12 Slacked lime ..66 6 Gutta percha . . 16 16 16 Rousseau's solutions of gutta percha and their use. 19 290 INDIA RUBBER, GUTTA PERCH A, BALATA. Gutta perch a, to which linseed oil has been added, is heated in a suitable vessel over an open fire. Linseed oil generally absorbs one-tenth of its weight of gutta percha. When a white cotton fabric is dipped into this solution it will be thoroughly penetrated by it, and, after it has become cold, will be of a yellowish color, transparent and very soft. Such material can afterwards be printed with all kinds of colors. Whiting, ochre, lampblack, etc.. may be added to the solution for the purpose of thickening and coloring it, which will also remove the peculiar odor of the gutta percha. For lacquering leather, coating of taffeta and gauze, some copal varnish, to which the gutta percha imparts its softness and elasticity, must be mixed with the solution. It can be mixed with all substances gutta percha especially exerting no influence whatever upon oil paints. Chattertoris gutta percha compound. This com- pound is employed for uniting the different coatings of gutta percha cores, and for cementing gutta percha to wood, etc. It is prepared as follows : Stockholm tar, i part, by weight, and about the same weight of rosin, are put into a jacketed vessel heated by steam, strained when melted and inti- mately mixed with f part by weight of cleansed gutta percha in shreds or thin pieces. The whole is worked together by horizontal stirrers, fixed on a vertical shaft. CHAPTER XIII. RUBBER AND GUTTA PERCHA WASTE AND ITS UTILI- ZATION. THERE will always be a certain amount of waste in manufacturing articles from rubber and gutta percha, no matter how carefully the work may be done, and the materials being expensive, means should be found of turning this waste to account. A distinction must be made between waste from pure and from vulcanized rubber, and care should be observed to keep them separate, because while the working-up of one kind of waste is quite simple, and there is but little difficulty in deciding how it can be utilized to the best advantage, a mixture of dif- ferent kinds of waste frequently presents consider- able difficulty in working, and besides a mass of little value is finally obtained which is only fit for articles of very ordinary quality. The utilization of pure crude rubber waste is a very simple matter, it being only necessary to form it into lumps and to pass these again through between the rolls. The material thus obtained frequently possesses a higher degree of plasticity than that originally used. Waste of vulcanized rubber is comminuted as much as possible by mechanical means, a grating (291) 292 INDIA RUBBER, GUTTA PERCHA, BALATA. apparatus or hollander being generally used for the purpose, and then mixed with pure rubber cut up into very small pieces. The materials are then mixed, which is done by repeatedly passing the heated mass through between rolls, while at the same time sufficient sulphur is added to vulcanize the pure rubber to the same extent as the waste. The mass must be worked until it is so uniform that the separate parts cannot be distinguished from each other by the naked eye, and then articles may be fashioned from it in the usual manner, whicli are finally vulcanized by subjecting them to the heat- ing process. According to another process the waste is first cut up into small pieces. These are boiled for several hours in caustic soda for the purpose of desulphur- izing them. But this can only be done in a satis- factory manner when the pieces are very small, and the boiling is continued for a sufficiently long time. In order to knead the waste, after it has been boiled, together with rubber, it is only necessary to continue the boiling until the pieces again possess the property of sticking together when heated. It is claimed that by Aco's process, not only waste of ordinary vulcanized rubber can again be utilized but also that of hard rubber. 220 pounds of waste are treated in a closed vessel for two hours with a mixture of 22 pounds of carbon disulphide, and 495 pounds of spirit of wine. It is claimed that by this manipulation the mass becomes sufficiently softened to allow of its being mechanically treated by masti- cating and kneading. WASTE AND ITS UTILIZATION. 293 If this process could be used just as described, it would surpass all others in regard to simplicity. But the results of many experiments have always been that many difficulties arise which can scarcely be overcome, and especially when hard rubber is mixed with the waste. If the work is to be done by this process, it is at least necessary to sort the pieces of hard rubber from the waste and to treat them by themselves. But the simplest manner of utilizing hard rubber waste is to melt it and work it into varnish, as described in a previous chapter. Another method of utilizing vulcanized rubber waste is as follows : The waste is comminuted as much as possible and is then exposed to a tempera- ture of 572 F., until a plastic mass has been formed. Heating is effected by steam which is passed through a cylinder containing the small pieces of waste. Eleven pounds of the plastic mass obtained are mixed with two ounces of palm oil, six ounces of sulphur and two pounds of white lead or magnesia, chalk or oxide of zinc. Articles moulded from this mass are subjected to the heating process. In conclusion, Newton's method may be men- tioned. The waste is treated in a well-closed vessel with camphene. It is allowed to remain in the vessel for fourteen days, and is then heated to about 158 F. to complete the action of the camphene. The greater portion of the solvent is then distilled off, and the tough mass remaining in the still 294 INDIA RUBBER, GUTTA PERCHA, BALATA. worked up. However, if the vulcanized rubber has been prepared with the assistance of metallic sul- phides, the result is not satisfactory. However, no matter what process may be used for the production of rubber mass from waste of vulcanized or hard rubber, the resulting product never possesses the properties demanded of a first- class material. It is therefore best to work it into hard rubber articles, of course after it has been comminuted in a suitable manner and mixed with pure rubber and sulphur. The disparity of quality is not so perceptible in these articles as in those of vulcanized rubber, which must possess a high de- gree of elasticity at all temperatures. Waste of gutta percha accumulating in the factory is more valuable than that of rubber, because it being as a rule pure, not mixed with foreign sub- stances and not vulcanized, it can at once be utilized. On the other hand, the value of old material is de- pendent on the degree of oxidation it has undergone and the chemical influences to which it has been exposed by the action of acids or very high tem- peratures. Such old material is frequently almost worthless, while, when it is only oxidized, it can be again made available by treatment with hot water to which caustic soda has been added, or with ben- zene or turpentine, by washing, kneading and mix- ing with fresh virgin material. CHAPTER XIV. EXAMINATION OF RUBBER ARTICLES. VERY few of the articles found in commerce are made of pure rubber, most of them containing abundant additions of other less valuable inorganic or organic materials, such as chalk, gypsum, heavy spar, oxides of zinc and iron, cork meal, oil, paraf- fine and similar substances. These additions are made to such an extent that many articles may be designated as an admixture of rubber combined with mineral powder. It is difficult to decide how far these admixtures are to be considered serviceable or as adulterations, since the articles, according to the demands on them, must consist of pure material or must receive various additions. Thus, according to Kissling, a packing ring for steam pipes should have a different composition from a gas tube, or a man-hole ring for a compressed air receiver. A valve which has to resist the action of strong min- eral acids must be made of a different mixture from a so-called oil-resisting rubber article. However, there is still considerable confusion regarding the question how large the percentage of rubber in a technical article intended for one or the other pur- pose must be. The determination of the specific gravity affords (.295 ) 296 INDIA RUBBER, GUTTA PERCHA, BALATA. a clue to the extent of the admixtures. Since pure rubber and pure gutta percha are specifically lighter than water, massive articles of pure materials will float upon water. By the addition of the sulphur required for vulcanizing, the specific gravity is somewhat increased, but only in so far that the articles, if they contain no other admixtures, still float upon water, or are only slightly specifically heavier than water, while by the addition of min- eral substances the specific gravity is considerably increased, as shown by the following determina- tions : Specific gravity. Content of ash, Quality of per cent. gas tubes. 0.98 0.66\ 0.99 2i83 I very good tubes. 1.05 2.00 ordinary tubes. 1.20 19.00 gray-black, inferior quality. 1.17 24.60 \ gray-black, cracks readily, 1.20 25.00 f but elastic. 1.26 34.30 gray, very bad. 1.52 38.60 red, becomes brittle in a short time ; very bad. The ash consisted of zinc oxide, chalk and ferric oxide, the latter predominating in the red tubes. Although according to these figures the specific gravity alone is not sufficient for the determination of the quantity of admixtures present, it throws enough light upon the subject so that the question whether the article has been artificially weighted to a smaller or greater degree can be accurately an- swered, and for this purpose an approximate deter- KXAM1XATION OF RUBBER ARTICLES. 297 mimition suffices. This determination is made by placing the material, cut up in small pieces, in water to which a sufficient quantity of a readily soluble salt is added until the solution has acquired such a density that the pieces of rubber, when stirred, neither sink to the bottom nor rise to the surface, but float in the fluid in all positions. The fluid then has the same density as the rubber to be tested. It is only necessary to filter the fluid through a dry filter and to determine the specific gravity of the filtrate by means of a hydrometer. An accurate examination of rubber articles pre- sents great, partly insurmountable, difficulties. Even if the admixed organic substances are tempo- rarily left out of consideration, many complications appear in the determination of the mineral con- stituents. For instance, if zinc oxide has been used as a filling material, by ignition a reduction an4 volatilization of metallic zinc may take place; sili- cates containing water, for instance, talc, when ignited, yield their water, and the content found is too small ; the sulphur may form metallic sulphides or sulphates ; carbonates, white lead, chalk, etc., yield their carbonic acid entirely or partly. For determining the total quantity of filling sub- stances, it is best to dissolve the rubber in petroleum and to examine the residue, whereby, however, it has to be taken into consideration that by this treat- ment a portion of the sulphur passes into solution. For the examination of pure rubber, vulcanized with sulphur alone, the determination of sulphur 298 INDIA RUBBER, GUTTA PERCHA, BALATA. suffices in order to find the quantity of sulphur- present. Unger gives directions for examining articles vulcanized with pentasulphide of anti- mony, which is very frequently a varying mixture of pentasulphide of antimony with free sulphur and sulphate of lime, the content of free sulphur which can be extracted with carbon disulphide amounting to from 6 to 30 per cent., and that of sulphate of lime to from 9 to 62 per cent. It may also be re- marked here that not only commercial pentasul- phide of antimony contains sulphur which can be extracted with carbon disulphide, but it has also been found, by Wilm, in varying quantities in preparations of pentasulphide of antimony made in various ways and with the greatest care. In ex- amining such articles the determination of the total sulphur of the antimony and calcium must be taken jnto consideration. Determination of sulphur. Weigh off 0.5 to 0.55 gramme of the sample and cut it up into about 100 small pieces. Prepare a mixture of 12 grammes of finely pulverized cupric oxide and 2 grammes of chemically pure, anhydrous carbonate of soda. Then place upon the bottom of a porcelain crucible a layer of pure cupric oxide, and upon this a layer of the mixture. Press into the latter about 8 pieces of the rubber so that they do not touch each other and are about 3 to 4 millimeters from the sides of the crucible. Upon this place another layer <>(' mixture and distribute in it in the same manner 10 pieces of rubber, and continue thus until all the EXAMINATION OF RUBBER ARTICLES. 299 rubber has been brought into the crucible. Cover the last layer slightly with mixture and pure cupric oxide. The crucible should not be excessive!} 7 large and the pieces of rubber should be as uniformly as possible distributed. Cover the porcelain crucible with a platinum lid, place it in a platinum crucible and heat at first very slowly, whereby the rubber melts and penetrates the surrounding mass. Heat- ing is continued for some time, but no gray smoke should escape, and only a peculiar odor reminding one of fennel should be diffused. After moderate heating for about half an hour, the crucible is brought to a red heat for about 10 minutes, when it is allowed to cool, and the contents are dissolved in hydrochloric acid with an addition of nitric acid. The fluid is reduced to dryness in the water-bath whereby antimonic acid in an insoluble form is separated. The residue is taken up with about 600 cubic centimeters of water and, after filtering, com- pounded with barium chloride to precipitate the sulphuric acid, which is determined in the usual manner. According to H en riques, correct results are not obtained by fusing with soda and saltpetre, because with too small an addition of saltpetre, sulphur is volatilized with the escaping gases, or with larger quantities explosions readily occur. To avoid both, it is recommended to bring about 20 cubic centi- meters of fuming nitric acid into a small porcelain dish, which is covered with an inverted funnel, and introduce gradually 3 to 4 grammes of the rubber 300 INDIA RUBBER, GUTTA PERCHA, BALATA. in fine shreds. A violent evolution of gas takes place and the rubber is destroyed. When decom- position is complete, the excess of nitric acid is re- moved by evaporation upon the water-bath, and the residue is mixed with about 4 grammes of a mixture of 3 parts potassium nitrate and 4 parts soda, and fused at a gentle heat. The residue is taken up with water, and after adding hydrochloric acid, evaporated to dryness, to separate silicic acid and, in the solution filtered from it, the sulphuric acid is determined. In the presence of lead or bar- ium combinations, sulphate of lead or of barium is found with the silicic acid and has to be separated from it. Determination of antimony. Put in a porcelain crucible about 1J grammes of the sample cut up in very small pieces, together with 10 grammes of crys- talized calcium sulphide. Heat, at first gently, and when foaming ceases more vigorously, and finally bring to a gentle red heat, stirring occasionally with an iron wire. After cooling take up the fused mass with water, filter off separated coal, etc., filter and super-saturate the filtrate with hydrochloric acid, whereby a mixture of antimonious sulphide and sulphur is precipitated. This mixture is collected upon a weighed filter, dried at 212 F., weighed, and in a portion taken from the filter and weighed? the antimony is determined. Determination of calcium. Ignite the rubber in an open porcelain crucible until a white ash remains behind. This is lu ated with hydrochloric acid, the EXAMINATION OF RUBBER ARTICLES. 301 resulting fluid compounded with an abundant quan- tity of hot water, supersaturated with ammonia, whereby antimonious oxide is separated, after filter- ing precipitated with oxalic acid, and from the separated calcium ^oxalate the quantity of calcium is determined. In a sample of rubber, Unger found by this method : Sulphur . . . 5.72 per cent. Antimony . . . 6.813 percent. Calcium . . . 0.3046 per cent. The calcium is calculated to sulphate, the anti- mony to pentasulphide, and the remaining sulphur taken into account as such. According to this the sample examined would contain : ]l.:'.o5 per cent, pentasulphide of antimony (with 4.542 per cent, sulphur). 1.310 per cent, gypsum (CaSo 4 .2H 2 . . (with 0.244 per cent, sulphur). 0.934 per cent, sulphur (with 0.934 per cent, sulphur). 86.401 per cent, rubber (with 5.720 per cent, sulphnr). 100.00 per cent. It is doubtful whether in rubber vulcanized at a high temperature, crystallized calcium sulphate with 2 molecules of water is present, and it would be more correct to take gypsum in an anhydrous state into the calculation. From the result of the analysis, Unger calculates that the mass to be vulcanized consisted of rubber, 100 parts, and pentasulphide of antimony, 15.74, or perhaps more correctly, 16 parts, and that the pentasulphide used had the following composition : 302 INDIA RUBBER, GUTTA PERCH A, BALATA. Pentasulphide of antimony, 85.50 per cent.; gyp- sum, 9.63 ; free sulphur, 6.87. To ascertain the nature of other mineral filling- substances, a complete analysis of the ash has to be executed. With admixtures containing lead it must be taken into consideration that the sulphur is converted into sulphate of lead. For the detection of admixtures of organic sub- stances, such as cork meal, etc., it is advisable to subject thin sections previously swelled up as much as possible in carbon disulphide to a microscopical examination. For the detection of a content of oily substitutes which are frequently mixed in larger quantities with rubber, Henriques recommends to boil, from six to eight hours, 2 to 5 grammes of the substance, cut up in small cubes, with about ten times the quan- tity of alcoholic soda solution which contains 6 to 8 per cent, of sodium hydroxide. Only a very small quantity of rubber is dissolved, but the total quan- tity of the oily substances, together with a portion of the sulphur, passes into solution, while a part of soda present enters into an insoluble combination with the sulphur. III. BALATA. CHAPTER XV. HISTORY, OCCURRENCE AND USES OF BALATA. LIKE gutta percha, balata is the inspissated milky juice of a few plants of the family Sapotaceae, which, however, belong exclusively to the genus Mimusops. It was formerly considered identical with gutta percha, but it is distinguished from it by suffi- ciently characteristic differences to assign to it a more independent position. Balata became first known about 45 years ago, the first account of it being found in an article published in 1857, by Prof. Bleekrode, and in a communication made, the same year, by him to the Society of Arts. In these communications he designated balata as Sumatra gutta percha, and concluded that it was a product identical with that obtained from Isonandra gutta. In 1860, the Colon- ial Secretary of British Guiana forwarded to the Society of Arts a few specimens of balata collected by Van Hoist in Berbice, which were later on turned over to the Kew Museum. The same so- ciety having offered a prize for the best substitute .for gutta percha, received in February, 1864, other samples of balata from Sir William Holmes. In (303) 304 INDIA RUBBER, GUTTA PERCH A, BALATA. bis letter to the Secretary of the Society, Holmes states that at the International Exposition of 1862, he had exhibited about | Ib. of balata, which later 011 had been handed over to Charles Hancock, who had expressed a very favorable opinion in regard to it. This sample was also sent to the Kew Museum, and the same institution received other samples as follows: from James Collins, 18G8, from British Guiana; from Governor Longdon, 1874, from Trinidad, and from Im Thurm, 1882, from Deme- rara. In 1884, G. S. Jenman forwarded samples of balata, as well as balata milky juice, and of balata prepared by precipitation with alcohol. The genus Mhrmsops is distributed over almost the entire globe, but thus far trees yielding balata are only known to occur in America : In the Antilles and Bahama Islands (West Indies), in Venezuela, British, Dutch and French Guiana, and a portion of Brazil ; in Africa : On the west coast of the equa- torial region, Abyssinia, Angola, Madagascar and Mauritius; in Australia: In Queensland and New Zealand. Hence the home of balata is in an en- tirely different location from that of gutta percha. Mimusops Balata is the principal balata-yielding tree. It is indigenous to English, Dutch and French Guiana, Surinam,. Barbadoes and the An- tilles, Brazil (Amazon), Costa Rica. It is a largo tree, with a trunk about 6 feet in diameter, and furnishes a wood much sought after as a building material. The Dutch name Paardenfleseh (horse- flesh), is given on account of the wood being of the HISTORY OP BALATA. 305 color and having the appearance of horse-flesh. The hark is thick and rough, and the fruit is of the size of a coffee berry, sweet like a plum, and with a hard white kernel, which yields an oil bitter in taste. The leaves are glossy, oval and acumin- ated. The milk is drunk by the natives, and when diluted with water, used as cow's milk. The trees grow in groups, and in alluvial soil. Besides M/ in n tops Balata, the following varieties of MiiHUMjjM which yield balata may be mentioned : M. (/lolmMi, M. spec-iosa, M. Schimperi, M. Kiimmel; further Lucumus varieties: L. gigantea, L. fissilis, L. litxt'iociirjKi, L. laurifolia, L. procera, and finally a few varieties of Chrysophyllum. For obtaining the balata latex it is not sufficient to make simply incisions in the bark, as the milky juice of Mimusops is so thick and coagulates so rapidly that the incisions would soon be choked up. In Venezuela the collectors formerly sawed the trees off near the foot, raised them upon props, and placed vessels under them for the collection of the juice which exuded from numerous incisions made scarcely a foot apart from each other. By this bar- barous method about 7 to 13 Ibs. of balata were ob- tained from a tree of medium size. At the present time hand-presses, by which the bark is subjected to strong pressure, are used. One press yields in an hour 9 to 13 quarts of juice which is equal to from 4 to 7 Ibs. of dry balata. In Maturin, a region which embraces the Venezuelan provinces of Cumania, Barcelona, Guiana, and Isla Margarita, very large 20 306 INDIA RUBBER, GUTTA PERCHA, BALATA. trees are found from which by this process several hundredweight of balata are obtained. Hence this system of destruction is extraordinarily lucrative, and is so widely extended that, if continued, this source will soon be exhausted, notwithstanding the great abundance of balata trees in Maturin. In Dutch Guiana, especially in Surinam, the trees are tapped. The bark, up to a height of 20 feet, is provided with incisions which are connected with each other and so arranged that the juice from one gutter runs into the other until it reaches the lowest one, where it is caught in a calabash, from which it is later on poured into a larger vessel pro- vided 'with a handle, which is called "gooba." In this gooba the juice is carried to the settlement, and either sold as it is, or poured into shallow wooden evaporating dishes. As the water evaporates the surface hardens, and skins about J inch thick are formed, which are removed and hung up over lines to drain and dry. This drying requires several weeks, since every balata skin presents a hard sur- face which retards evaporation. A gallon of juice yields 4 Ibs. of dry balata. A tolerably skilled workman obtains *about 4 gallons of milk a day, and a very skilled one up to 10 gallons. In British Guiana the jnethod of gathering balata is more rational as far as the preservation of the trees is concerned. Several longitudinal incisions are made in the trunk of the tree, and the bark between them is removed. The liber or inner bark, however, is left standing, which makes the HISTORY OF BALATA. 307 formation of new bark possible. The most suitable method is to remove and leave the bark standing in alternate squares. The bark removed is then pressed, ,a medium-sized tree yielding by this method about 2 Ibs. of balata ; but it must be taken into consideration that this operation can be indefi- nitely repeated, since every succeeding year the pieces of bark previously left standing are taken. The juice flows most abundantly during the rainy sea- son, and it also coagulates more slowly during that period. The milk which is called, in British Guiana, " Purvio," is collected in wooden vessels, since iron vessels impart to it a. blackish color, which depreciates the commercial value of the product. Crude balata is gray, brown, or white-reddish with darker spots and veins ; in appearance it resembles dry skins and it feels soapy to the touch. Gray balata comes into commerce also in blocks about 32 inches long and 16 inches wide, but red balata only in sheets J to f inch thick. The sheets show the shape of the vessel used for evaporating the juice. The commercial article contains, as a rule, few foreign bodies, and little bark. Lime is frequently added, especially more recently where the natives adulterate the juice by an addition or water, and then add lime to give the product the necessary consistency. At an average the quantity of impurities amounts to 10 per cent. The balata from Mimuspps Balata and M. globosa are especially valued since, besides their great 308 INDIA RUBBER, GUTTA PERCHA, BALATA. strength, they posses the property of being ductile only in a very slight degree, which makes them especially suitable for the manufacture of belts. They bring as high and even a higher price than gutta percha. In his " Cantor Lectures on Gutta Percha," pre- viously referred to, Dr. E. F. Obach gives valuable statistical data regarding the price and export of balata from British and Dutch (Juiana. These data have been taken partly from government re- ports on the colonies and parti) 7 from communica- tions of the Director of the Colonial Museum at Haarlem, as well as from a report of Mr. Churchill, consul at Paramaribo, to the Marquis of Salisbury. For the period from .1885 to 1896, they are as follows : Export from Export from British Guiana. Dutch Guiana. Year. Cwts. Value . Year. Cwts. Value 1885 496 2213 1886 606 2979 1887 723 3498 1888 2219 14069 1889 30 116 1889 3245 15625 1890 1502 7951 1890-91 2025 10078 1891 1882 11950 1891-92 1039 6807 1892 2375 15086 1892-93 2120 11296 1893 641 5424 1893-94 1832 8283 1894 2132 18047 1894-95 1867 11484 1895 2(131 22281 1895-96 1424 8923 1896 2480 21000 Total. 17S96 951 S2 Total. 13673 101865 HISTORY OF BALATA. 309 The above table shows that the lowest average price of a pound of balata exported from British Guiana was 9.13 pence in 1885, and the highest, 14.17 pence, in 1888; while the lowest average price per pound exported from Dutch Guiana was 9.0-7 pence in 1889, and the highest, 18.14 pence in 1893 and 1896. It must, however, be taken into consideration that this calculation of price is based upon the declared value in the export har- bors. On the other hand the selling price in the European markets, Liverpool, London, Marseilh^r Rotterdam and Hamburg was considerably higher and, in London, varied during the last fifteen years for balata in sheets and blocks 1/1 to 2/6 per pound. The principal difference between gutta percha and balata shows itself in the manner in which the two products are influenced by the air. While gutta percha, by the action of air and light, be- comes rapidly resinous, hard and brittle, not only upon the surface, but also in the interior, if this action continues for some time, balata, under the same conditions, remains unaltered for a long per- iod. At the ordinary temperature it is softer than gutta percha, and after cooling, does not acquire the same degree of solidity. On the whole it cools slowly, and when mixed with gutta percha, trans- mits this property to the mixture. When heated it diffuses the same odor as pure gutta percha which has been slowly heated under water and then brought to boiling. Its specific gravity is 1.05. It can be cut like gutta percha. but is 310 INDIA RUBBER, GUTTA PERCHA, BALATA. tougher. It dissolves completely in turpentine, but especially so in benzene and carbon disulplride when heated. Like rubber and gutta percha, it resists caustic alkalies and acts in the same manner towards hydrochloric acid. By sulphuric acid it is carbonized. At the ordinary temperature it forjns a horn-like mass, but softens at 120 F., and in this state can be given any desired form. When the commercial article is purified by wash- ing in boiling water, to which a small quantity of acid has been added, and then in boiling alcohol, a mass is obtained which, when dissolved in carbon disulphide, filtered and evaporated, shows, according to Sperlich, the same composition as gutta percha namely : Carbon, 88.5 ; hydrogen, 11.3 per cent. Crude balata is worked in a manner similar to gutta percha, the same apparatus and machines being used. In most cases, however, the manipu- lation is much simpler, because balata, as a rule, contains fewer impurities than gutta percha, and besides it is not used for articles for such delicate purposes as the latter. Frequently simple washing in a hollander suffices as a preparation for further working. Some varieties furnish, when vigorously kneaded, a very homogeneous material which, how- ever, retains too much elasticity and remains ad- hesive. Purified balata is also less pliant than gutta percha and. without being mixed with the latter, can only be used for certain purposes. Un- mixed it is not suitable for covering wires for the purpose of insulation, and even when mixed with HISTORY OF BALATA. 311 the best quality of gutta percha it is of less value for this purpose than pure gutta percha of even second quality. On the other hand, additions of balata to gutta percha, and even to rubber, are very proper to give both of them qualities desired for certain purposes. Unmixed balata is used for the prepara- tion of matrices and moulds for galvanoplastic pur- poses, for shoe-soles, sweat-bands and particularly machine belts. For the manufacture of the latter it is especially suitable on account of its great tough- ness ; but, like gutta percha belts, they must not be used in very warm rooms, as otherwise they become sticky. The manufacture of balata belts is analogous FIG. 24. \ to that of rubber belts. The best quality of strong cotton tissue is used for the purpose, and is treated with prepared mass in the spreading calender or spreading machine, then folded together to the re- quired thickness, frequently provided with longitud- inal seams, and then pressed either in that state or after it has received upon one or both sides a cover- ing sheet. It is scarcely necessary to say that these belts do not require vulcanizing. The ends of this kind of belt can be joined together by a very sim- 312 INDIA RUBBER, GUTTA PERCH A, BALATA. pie joint, which is made as follows : Heat the two ends until they are sticky, then spread the belt out flat, Fig. 24, push the two ends so far one over the other that a cut made at an angle of 45 slopes both ends suitably towards each other, bring the edges | to 1 inch over each other, press with an iron, replace the now jointed belt in its original folds and subject the joint to pressure. When the joint is cold the belt can be placed in position and runs without pounding or knocking, and hence is especi- ally suitable for driving dynamo machines. INDEX. ABSOLUTE alcohol, preparation of, 69, 70 Accrah, 81, 82 Acids, behavior of gutta percha towards, 253. 254 Aco's process of utilizing waste, 292, 293 Africa, cut! ing down rubber trees in, 29 Africa, rubber plants of, 13 tapping rubber trees in, 32 African rubber, 79-86 Air, effect of, upon rubber, 63 Albane, properties of, 250 Alexandre, Cabriot and Duclos, first patent for the utilization of gutta percha, obtained by, 226 Alcohol, absolute, preparation of, 69, 70 use of, in coagulation, 52 Alstonia, 12 Alum, coagulation by, 49, 50 use of, in coagulation, 53 Amazon, Lower, mode of tapping rubber trees on the, 30-32 Upper, mode of tapping rub- ber trees on the, 32 America, rubber plants of, 13 American process of bleaching rubber, 163 receipt for artificial ivory, 165, 166 rubber, 74-79 Ammonia, liquid, addition of, to the latex, 36 Angola, coagulation of the latex in, 42,43 niggers, 85 Animal charcoal, bleaching gutta percha with. 2 79- 281 Animal charcoal, use of, for deo- dorizing vulcan- ized rubber, 145, 146 Antimony, determination of, 300 pentasulphide, 105 vulcanization with, 128 Apocynaceae, 10-12 Artificial ivory, preparation of, 159-166 whalebone, or balenite, 137, 138 Artocarpus, 10 Aruwimi, 83 i Asbestos, 105 \ Asclepiadeae, 12 Asclepias, rubber in the milky juice of, 7 1 Asia, cutting down rubber trees in, 29 tapping rubber trees in, 32, 33 Asiatic rubber, 86-88 ' Assahan,242 Assam, coagulation of the latex in, 46, 47 cultivation of rubber plants in, 16 rubber, 86. 87 Aubert and Gerard's process for making round rubber threads, 177-179 Australia, rubber plants of, 13 tapping rubber trees in, 33 Australian rubber, 88 BACJAN. 237, 238 Bahia, 76, 77 coagulation of the la- tex in, 46, 47 Balata and gutta percha, princi- pal difference between, 309 belts. manufacture of,3 1 1 ,312 (313) 314 INDEX. Balnta, crude, properties of, 307 working of, 310-312 export of, from British Gui ana, 308 Dutch Guiana, 308 history, occurrence, and uses of, 303-312 mode of obtaining, 305-307 price of, 309 specific gravity of, 309 statistics of, 308, 309 unmixed, uses of, 311 Balenite or artificial whalebone, 137, 138 Balloons, small toy, 171, 172 vulcanizing of, 125 Balls, rubber, 169 small solid, 171 Bands, vulcanizing of, 125 Banjer-massin, 238 Bassia Parkii, 229 Baumhauser's investigation of gutta percha, 251 Belts, balata, manufacture of, 311, 312 machine, joining the ends of, 311,312 vulcanizing of, 125 Benguela niggers, 85 Benzene, solubility of rubber in, 67 Berniard, experiments of, 3 Berthollet, studies of, 3 Besson, efforts of, 3, 4 Bicycle tires, 190-192 Billiard tables, cushions for, vul- canizing of, 125 Billiongs,^230 Bissao balls, 79 Bleached gutta percha, Cattell's, 281, 282 Bleaching gutta percha, 278-282 rubber, 160-164 Bleekrode, Prof., account of ba- lata by, 303 Bolungan, 240 Boots and shoes, water proof coat- ing for, 220 Borneo (Ben Koclen), 88 dambose, 62 Borneo Djambes, 88 rubber, 88 mode of obtaining, 29 Bornesite. 62 Borrache, 74 Boula-Balam, 243 Brass moulds, 126 Brazil, coagulation of the latex in, 43-46 preparation of rubber in, 35- 40 Bread fruit, 10 Breit, W., first submarine cable laid by, 227. British Guiana, export of balata from, 308 mode of obtaining balata in, 306,307 Buffers, vulcanizing of, 125 Bumba, 83 Burghardt's condensing appara- tus, 212, 213 Busira, 83 Buttons, composition for, 156 Butylene, 72 CABEQA de negro, 75 Cahuchu, 8 Calcium chloride, use of, in co- agulation, 52 determination of, 300-302 Calender, 107, 108 Callotropis procera, 12 Cameraria, 11 Camphor, 133 Caou-tchene, composition of, 72 Caout-Chou, 2 Caoutchouc, 1 mineral, 3 oil of, 69 bodies present in, 72 composition of, 71 Caoutchoucine, 69 composition of, 71 Carbon, decrease of, in rubber, 64 disulphide and alcohol, solu- tion of rubber by, 69, 70 objection to, as a sol- vent, 6S solubility of rubber in, 67 INDEX. 315 Carthagena, 77 Casamanza (Boalam), 80 (Gambia), 80 Cassava, 9 Castilloa, 9 coagulation of the latex of, 40, 41, 46, 47 cultivation of. 15 elastica, best development of, in Mexico, 23, '14 indigenous to Mexico, 22 seed of, 24, 25 Cattell's bleached gutta percha, 281. 282 Caucho, 77, 78 Cayenne, 77 Ceara, preparation of rubber in, 44, 45 rubber, properties of, 45 solubility of, 07 scraps, 9, 75, 76 coagulation of the latex in the preparation of, 43-46 Cecropia, 10 Central Africa, rubber plants of, 13 America, rubber plants of, 13 coagulation of the latex in, 46, 47 tapping rubber trees in, 32 American rubber, 78, 79 sheets, 78, 79 Ceylon, cultivation of Manihot in, 18 of Para rubber tree in, 18-20 rubber, 87 Chalk, 105 Champagne's varnish for morocco, 219, 220 Champion, efforts of, 4 Charcoal, animal, bleaching gutta percha with, 279- 281 use of, for deodor- i/ing vulcanized rubbir. 145, 146 Chattertou's gutta purcha com pound, 290 Chay, 229 Chemical and physical properties of crude rubber, 60-73 Chemical and physical properties of gutta percha* 246-254 Chiapas, rubber plantations in, 28 Chloride of iron, use of, in coagu- lation, 52 Chlorine, bleaching rubber with, 161-163 Chloroform, bleaching gutta per cha with, 278, 279 solubility of rubber in, 67 Chonemorphia, 12 Chromic acid, use of, in coagula- tion, 52 Cinnabar. 105 Clark and Miller, experiments of, upon gutta percha, 251, 253 Clark's patent felt, 208, 209 Cloth printing machinfs, jacket of pressure rolls of, 172, 173 Coagulation by alum, 49, 50 by artificial dry heat or fu- migation, 35-40 by combination of natural or artificial heat with chemical disintegration, 56-58 by moi^t artificial heat or by boiling, 40, 41 by natural heat, 41, 42 by natural heat; evaporation upon the human body, 42,43 by natural heat; evaporation upon other even surfaces than the ground, 43 46 by rest after the addition of four to five times the quan- tity of water. 47, 48 by skimming after the addi- tion of the same quantity of water, and a shorter or longer rest, 46, 47 by soap water, 50, 51 by sulphuric acid and sea salt, 50 experiment in, by Grandjean and Waser, 38, 39 316 INDEX. Coagulation of the latex, 33-60 summary of experience, and experiments in, 5860 Coal tar asphaltum, 138 Coating wires with gutta percha, 269-276 Cochin China, acclimatizing ex- periments in, 22 Coffigny. description of a plant by, 2 ' Coins, taking impressions of, 282 Cold vulcanization, 6. 110-114 bath for, 111 Coli, 241 Collins. J., on Strauss' process of coagulation, 49 Colon rubber. 78 Coloring substances, 129, 130 Columbia, cultivation of rubber plants in, 22 Virgen, 77 Combs, composition for, 155 Commercial gutta percha, 235-245 rubber, 73-91 Compound tires, classes of, 191 Compounds of gutta percha, 282- 286 of gutta percha and wood, 286, 287 of rubber and gutta percha, 282, 283 Congo, coagulation of the latex on the, 42, 43, 47, 48 cultivation of rubber trees on the, 20-22 Cords, square, from crude rubber, 173-176 from prepared rubber, 176, 177 Cork meal, detection of admixture of, 302 Corrosive sublimate, use of, i coagulation, 52 Costa Rica, cultivation of rubber plants in, 22 Cotonan, 241 Cousin, preparation of rubber by, 55 Cowrie copal, 133 Cross, Robert, journeys of, 15 Crude balata, properties of, 307 Crude balata, working of, 310-312 gutta percha, manner of ob tain ing, 230-235 treatment of, 255- 262 rubber, admixtures of, 92 characteristic peculiari- ties of, 109 chemical and physical properties of, 60-73 composition of, 61, 62 cutting up, 93-f>:> drying, 98, 99 manner of obtaining, 29-33 mechanical treatment of, 92-108 operation of purifying, 93 preparation of mixed mass from, 104, 105 removal of impurities from, 92, 93 rolling or washing, 95- 98 softening or superficial washing of, 93 specific gravity of, 61 square cords from, 173- 176 washed, further working of, 99-108 Cuidad-Bolivar, il Cultivation of rubber plants, 14-29 Cushions for billiard tables, vul- canizing of, 125 Cutting machines, 93-95 square cords from prepared rubber, 176, 177 up crude rubber, 93-95 Cynanchum, 1 2 D 'ALMEIDA, Dr. Jose, 225, 226 Dambonite, 62 Dambose, 62 Day, Augustine G., improved method of vulcanizing patented by, 6 Decolorizing rubber, 160-164 Deodorizing vulcanized rubber. 144-146 INDEX. 317 Deodorizing water-proof tissues, 204-206 Desulphurized vulcanized rubber, 146, 147 Deville, Dr.. observations by, 39 Dichloride of sulphur, preparation of, 112, 113 properties of, 113, 114 Dichopsis calophylla, 229 gutta, 228 Krantziana, 229 oblongifolium, 228 pustulatum, 229 Door knobs, composition for, 156 mats, vulcanizing of, 125 Double texture water-proof tis- ; sues, 192 Drum slicing machine, 256 Drying crude rubber, 98, 99 loss in. 99 Dumas's process of preparing very j thin sheets, 193 Dunlap tire, 191 Dusting hard rubber, 152, 153 Dutch Guiana, export of balata from, 308 mode of obtaining ba- lata in, 306 Dye works, printing rolls for use in, 172 EAS.T Africa, coagulation of the latex in, 41, 42, 43 rubber plants of, 13 Ebermayer, hard rubber combs examined by, 155 Ebonite, 65 moulds, 126 Ecuador scraps, 79 Elastic gum wine, 2 webbings, fabrication of, 209-212 Electric wire and cables, machine for insulating, manufactured by John Royle & Sons, 273-276 Emery, conversion of, into fine powder, 141, 142 Enamel, rubber, 142-144 Enameling hard rubber, 153 Enamels, rubber, colored, 143, 144 England, re-export of gutta percha from, 244, 245 Entrefina Para, 74. 75 Equator, 83 Esquebo, 77 Ether, solubility of rubber in, 67 Euphorbia, 9 Euphorbiacea?, 8. 9 Eupione, 72 Examination of rubber article*, 295-302 FAUJAS de St. Fond, investi- gations of, 3 Felt paper, 208, 209 Ferric oxide, 105 Ficus, 9, 10 coagulation of the latex of. 46, 47 cultivation of, 14 elastica, 2, 10 Filling substances, determination of the total quantity of, 297 Fine cut sheet, adulteration of. 104 invention of. 103, 104 sheets, 101 commercial thick- nesses of, 103 Para rubber, 74 Filtering gutta percha solution, 279-281 Flint, conversion of, into fine powder, 141, 142 Fluavile, composition of, 250, 251 Foucroy, studies of, 3 Fresneau, researches of, 2 Fry, C., patented method of, for dissolving rubber and gutta percha, 70 Fumeiro. the, 36 Fumigation, coagulation by, 35- 40 Fusel-Aublet, work of, 2 GABOON balls, 82 tongues, 82 Gambia balls, 80 coagulation of the latex in. 55-58 318 INDEX. Gerard's process of vulcanization, 115-117 Gerner's preparation of hard rub- ber, 133, 134 Getah muntali, 235 Gilder's varnish for, 219 Giobert, studies of, 3 Glass, conversion of, into line powder, 141-144 Goodyear, Cha?., discovery of vul canizing by, 5 hard rubber invented by, 6 vulcanizing process invented by, 117, 118 Grand Bassarn, 8 1 Grandjean and Waser. experiment of, 38, 39 Graphite, 141 Grinding and polishing composi- tions, 139-142 and polishing compositions, form of, 142 compositions, preparation of, 141 Grossa, 74, 75 Grossart, invention of, 3 Guatemala, coagulation of the latex in, 55, 56 rubber, 79 Guayaquil, 78 Guiana, preparation of rubber in, 35-40 Gum wine, elastic, 2 Gutta, composition of, 250 percha, 224-290 and balata, principal difference between, 209 and rubber compound for machine belts, 283-285 waste, and its util- ization. 291-294 and wood, compound of, 286, 287 appearance of best known varieties of, 236, 243 best known varieties of, 237-243 bleached, Cattell's, 281, 282 Gutta percha, bleaching of, 278- 282 chemical and physical properties ot, 246- 254 indifference of, 253 coating wires with, 259- 276 commercial, 235-245 names of, 236-243 composition of, 249 compound, Chatterton's, 290 compounds, 282-286 crude, manner of obtain- ing, 230-235 treatment of, 255- 262 c utting up, 256 disguising the odor of, 286 export of, from Singa- pore, 243, 244 extraction of, 234, 235 forms of, in which brought into com- merce, 236-243 Fry's patented method for dissolving, 70 hard, compounds, 285, 286 historical review of, 224-227 hose, 264-267 machine for,264, 265 industrial application of, 263-277 kneading machine for, 258, 259 loss of, by washing and kneading. 262 moulil ing articles of, 264 occurrence of, 227-230 plants, geographical dis- tribution of, 230 plants, most impor- tant. 228-229 preparation of. 2.'>1. 2.'!2 of, for storage, 260, 261 press or strainer for, 260 INDEX. 319 Gutta Percha, principal markets of, 245 properties of best known varieties of, 23G-243 quantities of, brought to Singapore, 243 solution, filtering of, 279-281 solutions, R o s s e a u's, 289, 290 statistics of, 243-245 structure of, 248 threads, 267-269 unmixed. scarcity of, 232 uses of, 263-264 vulcanization of. 276, 277 washing machine for, 257, 258 yield of, 233 vierge, 242 HANCOCK, Thos., investiga- tions of, 4 Hancock, Thos., process of vul- canization, invented by, 6 warm vulcanization invented by, 114 Hancornia, 11 coagulation of the latex of, 46, 47 Ilanausek, T. F., experiments of, on the solubility of rubber, 67 Hard gutta percha compounds, 285, 286 rubber, 65, 148-166 coloring, 152 compositions for, 155 dusting of, 152, 153 enameling, 153 Gerner's preparation of, 133, 134 invention of, 6 lacquer, 222, 223 moulding articles of. 140, 150 moulds, 120 physical and chemical properties of, 158, 159 plating, 153 uses of, 149 Hard rubber, vulcanizing, 150- 152 waste, utilization of, 154 Hay ward, uses of flowers of sul- phur by, 5 Heat, artificial dry or fumigation, coagulation by, 35-40 behaviour of rubber in, 7173 Heater, vulcanizing, 121-123 Heavy spar, 105 Hemp, ground, 105 seed, 133 Henriques' method of detecting oily substitutes, 302 of determining sul- phur, 299, 300 Herissant, investigations of, 2, 3 Hevea, 8 brasiliensis, 8 chemical composition of the latex of, 61 cultivation of, 15, 16 of, in Ceylon, 18-20 properties of the fresh latex of, 60, 61 composition of the milky juice of, 37 guyanensis, 2, 8 latex of, experiments in treat- ing the, 51-54 Heveene, composition of, 72 Historical review of rubber, 1-6 Hoehnel, Dr. F. von, and Collins Jones, various methods of coag- ulation described by, 34 Hollow articles, 169, 170 Hose-forging machines, 266, 267 gutta percha, 264, 267 rubber, 179, 180 small, manufacture of, 182, 183 vulcanizing of, 125 with layers of wire. 182 Howison, James, 2 INDIA, cultivation of rubber plants in, 14, 15 India rubber, 1-223 occurrence of, 7-14 plants of, 13 320 INDEX. Indian Archipelago, cutting down rubber trees in. 2! Industrial application of gutta percha, 263-277 Insulating electric wire and ca- bles, machine for. 21'.', -27<> Iodine, tincture of. use of, in co- agulation. 53 Ipomoea bona nox, 56 Iron, chloride, use of. in coagula- tion, 52 Isonandra gutta, 22S Isoprene, composition of, 72 Isthmus of Tehuantepec, Castil- loa elastica indigenous to, 22 Ivorv, artificial, paeparation of. 159-166 black 10f, JATROPA elastica, 8 Java rubber, 87, 88 Jebe, 74 Jeffery's marine glue, 222 Johnson's hard rubber mixture, 157 method of preparing water- proof tissues. 196 Jungfleisch. E., experiments of, in extracting gutta percha, 234, 235 KAMPTULICON. preparation of, 133-136 Kassa'i. noir, 82 in balls, H3 rouge, 82 strips, 83 Kelatin, 241, 242 Kew Botanical Garden, cultiva- tion of rubber plants in the, 15 Museum, specimens of batata received by, 303. 304 Kneading machines, 258, 25!) Knife handles. composition for, 156 Knives, sharpening and polishing compositions for. 1 to Kotaringin, 238 LA COXDAMINK. researches of, 1.2 Lacquers and varnishes, rubber, 214-223 Lacquer, hard rubber, 222, 223 leather, 2 is La Grenee, introduction of gutta percha by. 2 2 6 Lamp black. 1 05 Landolphia, 1 1 coagulation of the latex of. 47, 4H Latex, addition of liquid ammonia to. :-',<) chemical disintegration of. by mineral reagents, 48-54 by addition of vegetable agents. 55, 5; coagulation of the, 33-HO of, by alum. 49. 5