Main! 
 
 LIBRARY 
 
 UNIVERSITY OF CALIFORNIA. 
 ^eceiveJ JUL 10 1895 ... 189 
 
 ^Accessions No.u?fl*5~ /&. Class No. 
 
 

THE 
 
 ALKALI TRADE 
 
LOS DOS : PRINTED BY 
 
 SPOTTI6WOODK AND CO., NEW-STREET SQU4.EE 
 AND PARLIAMENT STREET 
 
THE 
 
 HISTORY, PRODUCTS, AND PROCESSES 
 
 OF THE 
 
 ALKALI TEADE 
 
 INCLUDING THE MOST RECENT IMPROVEMENTS 
 
 BY 
 
 CHAELES THOMAS KINGZETT 
 
 \ 
 
 (CONSULTING CHEMIST) 
 
 WITH 23 ILLUSTRATIONS 
 
 LONDON 
 LONGMANS, GEE EN, AND CO. 
 
 1877 
 
 All ri'jhlt rt.-ft>rve<i 
 
PEEFACB. 
 
 IN the following pages I have endeavoured to give a 
 concise but comprehensive account of the largest branch 
 of chemical industry of this country. 
 
 Importance has been attached in this attempt, to 
 matters of history, interesting as they are in showing 
 how gradually knowledge is perfected. It will, for in- 
 stance, be seen that at no time in the history of the 
 Alkali Trade has an inventor brought into use a totally 
 new process ; so-called new processes are but the per- 
 fected forms of old ones, and are based upon previously 
 known facts. Moreover, the greatest commercial suc- 
 cesses have been achieved, not by the practical appli- 
 cation of new ideas, but in the development of old ones. 
 Taken as a whole, this trade well exemplifies the truth 
 that scientific investigations necessarily precede industry. 
 
 Men, from time to time, discover new facts, either by 
 following out a process of induction constructed upon 
 a knowledge of the relations existing between previously 
 known facts, or by accident. Accidental discoveries 
 are somewhat inevitable in experimental science, where 
 the method of enquiry depends upon reasoning, for the 
 correctness of which there is no absolute test. But for 
 
vi PREFACE. 
 
 science and humanity it is all one, no matter what be 
 the instrument of discovery, so long as discoveries are 
 effected. For in their time, other men arise, and in the 
 course of their studies find the explanation, where before 
 there was only known the fact, and with such advances 
 there sometimes ensues a generalisation, a law, or a new 
 method of enquiry. Simultaneously, progress in industrial 
 applications is made. 
 
 In discussing, therefore, the value of abstract scien- 
 tific work, those who engage in such discussion must be 
 further prepared to discuss the good for humanity of all 
 progress, not only in industry and commerce, but in 
 every direction of civilisation. Such questions, in fact, 
 lead only to the doctrine of evolution and the idea of 
 eternity, and while first and final causes are alike hidden 
 from us, we cannot withstand the march of progress. 
 
 With this idea before my mind, I have not hesitated, 
 therefore, to bestow considerable attention in this work, 
 to propositions and suggestions for improved processes, 
 which have not as yet, and perhaps never may be, 
 adopted in practice. 
 
 The processes which are actually in use have been so 
 described, that while scientific accuracy has in no case 
 been sacrificed, many technicalities have been avoided, 
 in order that the accounts should be readable alike to the 
 outside public, and to those engaged practically in the 
 trade. To the latter class of readers, it is hoped that 
 the book will be useful as a record of the state of the 
 trade, and as a suggestive work of reference. 
 
PREFACE. Vli 
 
 In order to make the book as complete in itself as 
 possible, beyond the history and descriptive accounts of 
 the various processes, I have given attention to the uses 
 of the products in other arts and manufactures. Particular 
 stress has also been laid upon waste products and their 
 possible utilisation, while the statistics in reference to the 
 trade will be found to accurately indicate its extent. 
 
 In parting with the book from my hands, I cannot 
 forget the valuable help I have received from my friend 
 Mr. George Chaloner, who, as editor of ' Iron/ bestowed 
 especial care and aid during the publication of the follow- 
 ing chapters in that Journal. 
 
 My thanks are also due to Mr. Eichard Cail and 
 Mr. Edmund K. Muspratt, the hon. secretaries of the 
 Soda Association, for having furnished me with some 
 valuable statistics. 
 
 To the other following gentlemen I desire to express 
 my gratitude, in some instances for drawings of plant, 
 and in others for useful information : Messrs. William 
 and John Glover, Mr. Walter Weldon, Dr. Sprengel, 
 Mr. James Mactear, Mr. W. Henderson, Mr. G. E. Davis, 
 Mr. Claudet, Mr. J. Cammack, and Messrs. Daglish & Co. 
 of St. Helens. 
 
 In conclusion, I trust these gentlemen will find justi- 
 fication for their kindness, in the work I now leave in the 
 
 hands of the public. 
 
 CHARLES T. KINGZETT. 
 
 ANALYTICAL AND CONSULTING LABORATOET, 
 
 1 VICTORIA STREET. WESTMINSTER, S.W. 
 
CONTENTS. 
 
 CHAPTER I. 
 
 INTRODUCTION. 
 
 PACK 
 
 Considerations regarding industry in its bearing on the wealth of na- 
 tions Historical notes on English chemical industry Progress of 
 pure chemical science Patent laws and Governmental recognition 
 of science Scheme of the English alkali trade Remarks on manu- 
 facturers and the conduct of works Contrast of the trade in Eng- 
 land and Germany . . . . . . 1 
 
 CHAPTER II. 
 
 PYRITES, SULPHUR, AND NITRE, AND THE HISTORY OF THE 
 MANUFACTURE OF SULPHURIC ACID TO 1840. 
 
 Natural deposits of sulphur and their origin Attempts to utilise the 
 sulphur in gypsum The use of pyrites, and their occurrence in 
 nature Statistics regarding pyrites Attempts to make artificial 
 pyrites Natural beds of soda nitre ; statistics History of sulphu- 
 ric acid to 1840 Manufacture of sulphuric anhydride . .11 
 
 CHAPTER III. 
 
 MANUFACTURE OF SULPHURIC ACID. 
 
 Pyrites burners (different forms) Nitre pots Dr. Sprengel's water 
 spray apparatus Sulphuric acid chambers Gay-Lussac's absorbing 
 columns Glover's towers The concentration of sulphuric acid 5 
 old and new methods Statistics of the trade Purification of com- 
 mercial acid Notes on the trade in the South of France Other 
 processes for making sulphuric acid , . , . .26 
 
X CONTENTS. 
 
 CHAPTER IV. 
 
 THE TREATMENT OF BURNT PYRITES ; EXTRACTION OF COPPER, 
 
 SILVER, AND GOLD j THE MANUFACTURE OF SULPHATE 
 
 OF COPPER. 
 
 Composition of burnt pyrites The Henderson wet process of copper 
 extraction Removal of arsenic from copper liquors Utilisation of 
 the sulphate of sodium in copper liquors Augustin's process for 
 extracting silver from its ores Claudet's process for extracting silver 
 and gold from copper liquors Chadwick and Jardine's improvements 
 on Henderson's process Mr. Gibb's process for extracting the silver 
 Dr. Hoffmann's improvements in the German trade Manufacture 
 of sulphate of copper . . . . . .4 
 
 CHAPTER Y. 
 
 HISTORICAL SKETCH OF ALKALI MANUFACTURE. 
 
 Ancient literature Natural soda deposits The old trade in kelp and 
 barilla Introduction of Leblanc's process and its history Statistics 
 of the soda trade . . . . . . .63 
 
 CHAPTER VI. 
 
 MANUFACTURE OF SALT, SULPHATE OF SODIUM, AND 
 HYDROCHLORIC ACID. 
 
 The uses and manufacture of salt Statistics relative to salt decom- 
 posed for soda-making Salt-cake furnaces Cammack and Walkers 
 and other improved forms of furnaces Jones and Walsh's improve- 
 ments Longrnaid's process Historical notes leading up to liar- 
 greaves' process Description of Hargreaves' process Other processes 
 for making sodic sulphate Manufacture of Glauber's salts . . 70 
 
 CHAPTER VII. 
 
 MANUFACTURE OF CARBONATE AND BICARBONATE OF SODIUM. 
 
 Analyses of salt-cake, limestone, ashes of slack, etc. Description of 
 hand-worked black ash furnaces Analyses of black ash Revolving 
 furnaces Mr. Mactear's improvements in the manufacture of carbo- 
 
CONTEXTS. XI 
 
 PAGE 
 
 nate of soda Losses of soda in the various processes Lixiviation of 
 black ash or crude soda Action of water upon ball soda Composi- 
 tion of vat liquors Production of soda ash, white alkali, soda crys- 
 tals, etc. Bicarbonate of sodium Statistics . . . .99 
 
 CHAPTER VIII. 
 
 MANUFACTURE OF CAUSTIC SODA. 
 
 Historical Notes The cauticising operation Composition and uses of 
 the lime-mud after causticising Concentration of the caustic lyes 
 Oxidation of the ' pots ' Salting down process Composition of 
 60 and 70 per cent, caustic soda ' Bottom ' caustic Red liquor and 
 cream soda ........ 118 
 
 CHAPTER IX. 
 
 ALKALI WASTE; REGENERATION OF THE SULPHUR; 
 MANUFACTURE OF HYPOSULPHITE OF SODIUM. 
 
 Alkali waste: its composition, etc. Various suggested processes for 
 effecting its utilisation, including those of Gossage, Duclo, Weldon, 
 etc. Mond's process for regeneration of the sulphur Mactear's pro- 
 cess for sulphur recovery Schaffner's refining apparatus Recovery 
 of the sulphur by means of alloxan Manufacture of fictitious pyrites 
 from alkali waste and burnt pyrites Manufacture of sodic hyposul- 
 ' phite . . . ." 1:33 
 
 CHAPTER X. 
 
 SODA PROCESSES OTHER THAN LEBLANC's ; INCLUDING THE 
 ' AMMONIA PROCESS.' 
 
 Processes of Hunt, Gossage, Arrot, Ward, etc. Manufacture of soda 
 from cryolite Tilghmann's and Fritzsche's processes Other pro- 
 . cesses Lunge's baryta process Improved form of Bachet's process 
 History and description of the ammonia process Davis's new phos- 
 phate of sodium process Manufacture of sodic phosphate . . 149 
 
 CHAPTER XI. 
 
 MANUFACTURE OF SOAP. 
 
 Historical notes regarding soap and its uses The chemistry of soaps 
 Fats and fixed oils Hard, soft, and silicated soaps Resin soap 
 Soap from the yelks of eggs Mottled soaps Statistics . . 169 
 
Xll CONTENTS. 
 
 CHAPTER XII. 
 
 HISTORICAL NOTES ON THE BLEACHING INDUSTRY. 
 
 PAGE 
 
 Ancient records of the art of bleaching State of this industry at the 
 end of last century Improvements introduced by Roebuck and Home 
 Influence of the discovery of chlorine Rationale of bleaching by 
 chlorine Lye of Javelle, or potassic hypochlorite Bleach liquor, or 
 calcic hypochlorite Bleaching powder Process of bleaching by 
 means of chloride of lime The constitution of bleaching powder 
 Suggestions for improvements in the bleaching powder trade . .178 
 
 CHAPTER XIII. 
 
 THE OLD PROCESS OF MANUFACTURING CHLORINE. 
 
 Various uses of hydrochloric acid Manganese ores and their sources 
 Early methods of generating chlorine Chlorine stills The process of 
 making chlorine prior to introduction of Weldon's process Elliott's 
 and Dunlop's methods for regeneration of the manganese M. Lau- 
 ren's method of making chlorine Shank's and Dunlop's chlorine pro- 
 cesses Longmaid's and Hargreaves' processes Other processes which 
 have been proposed . . . . . . 184 
 
 CHAPTER XIY. 
 
 WELDON'S CHLORINE PROCESS (a). 
 
 Statistical notes of the bleaching-powder trade Description of the Wei- 
 don plant and process Chemistry of the process Valentin's im- 
 provement in the oxidation of the manganese Consideration of 
 various so-called continuous reactions . . . . .196 
 
 CHAPTER XV. 
 
 WELDON'S MAGNESIA CHLORINE PROCESS (b). 
 
 Impetus given to chemical industry by the introduction of Weldon's 
 original process The defects of the last-named process Description 
 of the new process for obviating these defects Utilisation of dilute 
 chlorine ..... . 207 
 
CONTENTS. Xlll 
 
 CHAPTER XVI. 
 
 DEACON'S AND OTHER CHLORINE PROCESSES. 
 
 PAGE 
 
 Description of the Deacon process Various improvements effected from 
 time to time The difficulties of the process Hargreaves' and Robin- 
 son's chromate process ....... 216 
 
 CHAPTER XVII. 
 
 MANUFACTURE OF BLEACHING POWDER, BLEACHING LIQUOR, 
 CHLORATE OP POTASSIUM, AND EPSOM SALTS. 
 
 Purification of the chlorine gas Preparation of the lime Description 
 of the various chambers and the process Analyses of good and bad 
 bleaching powder Working results and statistics Notes on the 
 French trade Manufacture of bleach liquor Manufacture of chlo- 
 rate of potassium Improvements in this last manufacture Prepara- 
 tion of Epsom salts ....... 224 
 
 CHAPTER XVIII. 
 
 CHEMICAL CLIMATOLOGY, ETC. 
 
 The direct objects of manufacturers The Alkali Act "of 1863 The 
 Amendment of 1874 Improvements introduced by the use of Gay- 
 Lussac's and Glover's towers Recovery of manganese from still- 
 liquors, and sulphur from alkali waste Nuisance from coal-smoke 
 General remarks ... . 234 
 
 CHAPTER XIX. 
 
 STATISTICS OF THE ALKALI TRADE. 
 
 Fluctuations in prices and profits Past and present ralue of articles 
 Returns of 1861 Returns of 1866 Returns of 1867 (Tyne district) 
 Statistics relating to 1874 The chemical industry of Glasgow and 
 the Clyde Valley Table showing production upon 100 tons pyrites . 242 
 
LIST OF ILLUSTEATIONS. 
 
 FIGUUI-: PAGE 
 
 1-3. SHOWING CONSTRUCTION OF PYRITES BURNERS . 29, 30 
 
 4, 5. AN ARRANGEMENT OF TWENTY SETS OF BURNERS, 
 
 WITH NITRE POTS, AND GAS CONDUCTING PIPES . 30, 31 
 
 6. ' NITRE POT ' COMMONLY EMPLOYED . . . 33 
 
 7. SPRENGEL'S ' WATER SPRAY' APPARATUS . .37 
 8, 9. GLOVER'S DENITRATING TOWERS . . . 44 
 
 10-12. PLAN AND ELEVATION OF DECOMPOSING POT AND 
 
 ROASTER FOR MAKING 'SALT CAKE' . . 83,84 
 
 13, 14. PLANT USED IN HARGREAVES' PROCESS FOR MAKING 
 
 ' SALT CAKE ' . . . . to face 92. 93 
 
 15,16. ENGRAVINGS OF REVOLVING 'BLACK ASH' FUR- 
 NACE ..... to face 105 
 17. ENGRAVING OF REVOLVING 'BLACK ASH' FUR- 
 NACE . . . . . . . 105 
 
 18, 19. CAUSTIC SODA ' POTS' .... 126 
 
 20. APPARATUS FOR MELTING SULPHUR BY MEANS OF 
 
 STEAM . . . . . . 144 
 
 21,22. PLANT USED IN WELDON'S PROCESS OF CHLORINE 
 
 MANUFACTURE . . . . .199, 200 
 
 23. WELDON'S MANGANESE REGENERATION PLANT (PLAN) 
 
 to face. 200 
 
HISTOKY, PRODUCTS, AND PROCESSES 
 
 OF 
 
 THE ALKALI TRADE. 
 
 CHAPTER I. 
 INTRODUCTION. 
 
 THE WEALTH of a nation may be said to be indicated by 
 the magnitude of its commerce. This must have been so 
 from the earliest times, although the several factors upon 
 which all commerce is based, must individually and re- 
 latively have possessed very different values to those now 
 attached to them. These factors are natural products, 
 agricultural products, and manufactured products. 
 
 Could we go back sufficiently far in the history of 
 nations, we should come to a time when commerce meant 
 literally the exchange and barter of the commonest natural 
 products ; but as the peoples progressed in civilisation so 
 must their requirements also have increased, and to meet 
 these requirements it became necessary to apply to natural 
 products certain processes based on a study of natural 
 laws, in order to shape those articles to the desired uses. 
 But so small must have been the extent of such modifi- 
 cations of natural products as scarcely to merit the name 
 
 B 
 
Z THE ALKALI TRADE. 
 
 manufactures, while they, beyond doubt, represent the 
 first germs of that which has become the most important 
 factor in the commerce of nations. While in such times 
 it was possible for much to be accomplished through 
 agriculture, yet even in this direction the improvements 
 had to keep step with the march of time, until now agri- 
 cultural products may be said to be not only the increase 
 of the earth, but the increase of the earth as controlled 
 and guided by the intervention by man, of scientific 
 applications. 
 
 . Passing on to consider more in detail the history of 
 manufactures, we will confine ourselves more especially 
 to those which have chiefly developed through chemical 
 knowledge being brought to bear upon them ; and it will 
 not be without interest to take a brief retrospect of the 
 rise and progress in this country of that important branch 
 of manufacture, known as the Alkali Trade, before pausing 
 to study in detail its various ramifications. 
 
 The study of manufactures during the Middle Ages 
 is attended with the greatest interest, for by it we are 
 enabled to perceive how industry and science go hand 
 in hand. Improvements in manufacturing industries can 
 only arise through the application of new knowledge, 
 which latter can only be attained through the method of 
 experiment. Of such a method the ancients were in want ; 
 hence, we find, in very early times, when the alchemists 
 evaporated common water, and obtained a residue, that 
 residue was regarded as a product of transformation of 
 the water, a perfectly legitimate conclusion, when we 
 consider that they had no knowledge of the power of 
 certain liquids to dissolve certain substances. 
 
 Looking back over the pages of English history, we 
 
POLITICAL INFLUENCES ON TRADE. 3 
 
 find that in the fifteenth century our chief exports were 
 wool, sheepskins, and leather, while our imports were 
 wines, silks, spices, and precious metals. There was also 
 a considerable iron trade carried on in Sussex, which con- 
 tinued to prosper for several centuries. 
 
 In the seventeenth century English commerce suffered 
 vastly from the system of monopolies, which was not 
 abolished till the time of the Long Parliament, but even 
 at that early date, Manchester was famed for its cotton 
 manufactures, while our silk and cloth industries were 
 greatly improved by the French Protestants who, after 
 the Eevocation of the Edict of Nantes, found in England 
 a refuge and a home (1685). About the same date, 
 banking and the modern system of the post-office origi- 
 nated. Nearly a century later, spinning machines were 
 invented (1769) ; in the same year Watt patented the 
 steam-engine ; and in 1785 the power-loom was intro- 
 duced ; moreover, the country was intersected by canals, 
 which greatly benefited the inland trade. 
 
 These discoveries and improvements constituting the 
 essentials of progress in industries, were only contem- 
 poraneous with scientific discoveries. While Watt was 
 studying the steam-engine, the chemists in their labora- 
 tories were not idle. Chemistry was already far removed 
 from its birth, and instead of alchemical experiments and 
 wild speculations on the transformation of metals and the 
 ' philosopher's stone,' there was substituted the discovery 
 of natural laws by experiments based upon reasonable 
 hypotheses. Lavoisier and Priestley had determined the 
 true nature of oxygen, and the balance had been intro- 
 duced into chemical science. Scheele had in 1774, 
 discovered chlorine and its bleaching characters, and 
 
 B 2 ^^^ 
 
 0* THE 
 
4 THE ALKALI TRADE. 
 
 Chemistry itself may be said to have been no longer a 
 dark search after things removed from the mental grasp, 
 but henceforth a science whose function was the study of 
 the laws of changes of matter. It was henceforth required 
 that the amounts of the products of the changes should 
 be determined, and their relations to the original matter 
 established ; it was not enough to know that oxide of 
 mercury evolved oxygen on heating, but it was requisite 
 to ascertain how much oxygen a given quantity of oxide 
 of mercury could evolve. 
 
 But we must not dwell on this fascinating subject ; we 
 must pass on to consider Chemistry as a science built on a 
 framework which had been raised by the labours of such 
 >a men as Black, Lavoisier, Berzelius, Scheele, an d Priestley ; 
 we must pass on to consider the applications of derived 
 knowledge to the arts and manufactures. And having 
 done so, we appreciate as the natural consequences the 
 blessings of cheap soda and soap, c cheap light and cheap 
 cleanliness/ Neither can we stay to dwell on the strides 
 made in chemical science in more recent times ; but we 
 shall be enabled to appreciate the importance of such 
 progress when we proceed in future chapters to study the 
 industries to which the gained knowledge has been ap- 
 plied. Suffice it here to say, that Mr. Gossage has shown 
 that certain chemical industries have so developed, that 
 now by the consumption of a manufactured article, namely 
 soap, the civilisation of a country maybe estimated. Un- 
 fortunately it is not so pleasant to contemplate the lives of 
 those men who by their life-work have furnished such a 
 happy state of things. It may be said of most of them that it 
 was their fate to die ; unwept, unhonoured, and unsung ' ; 
 and especially of one is this true, and one of the most 
 
POSITION OF CHEMICAL SCIENCE. 5 
 
 deserving of men, for he it was who, at the moment of peril 
 to his country, opened to her, resources of wealth inesti- 
 mable resources hitherto unknown. It was Le Blanc ; he 
 who, after a life of poverty and hardship, lived for many 
 years in a foreign hospital, and finally perished by what 
 has proved the right arm of the alkali trade his own. 
 
 England is open to similar charges of neglect of its 
 best sons, and even now, in these days of boasted civilisa- 
 tion, no fact is more striking than that science is not 
 sufficiently recognised by the Government of this country. 
 It is and must be admitted on all sides that scientific 
 research necessarily precedes the application of science to 
 industry, and yet, even now, the pay of the chemist is 
 little or no better than the recompense of an unskilled 
 labourer. True it is that the patent laws afford some 
 protection to those who are in the position to patent, but 
 many even of our best chemists are not possessed of the 
 means, while for the most part chemical inventions and 
 discoveries do not admit of protection in this way. We 
 cannot imagine, for instance, Scheele patenting the mode 
 of preparation and uses of chlorine, and yet his discovery 
 has led to an industry, viz., the manufacture of bleaching 
 powder, of which substance this country alone produces 
 annually more than 100,000 tons. 
 
 We can only hope that the time is near at hand when 
 we shall have a Government sufficiently enlightened to 
 appreciate that it is to its best interests to foster and 
 encourage science in all its multiplicities, for by so doing 
 alone, can England maintain that supremacy over all other 
 nations which it now possesses in its varied industries. 
 
 With these preliminary observations we will now 
 return to our more immediate subject. The alkali trade 
 
6 THE ALKALI TRADE. 
 
 as now worked in Great Britain is planned out on the 
 adjoining scheme, and in the following chapters it will 
 be our endeavour to give a complete sketch of the history, 
 products, and processes involved in each branch, together 
 with some remarks on the uses of the manufactured 
 products. In doing this we shall pay especial attention 
 to those recent improvements which may be said to have 
 almost revolutionised the whole trade, by effecting the 
 utilisation of what were previously waste products, or by 
 their avoidance. While, therefore, the work will stand 
 alone as the only one of its kind, it is hoped that it will 
 serve as a basis for further thought and research by 
 chemists, who, as a body, may be safely said to be un- 
 acquainted with those chemical processes which form the 
 foundation stones of the alkali trade ; and if, in assisting 
 to destroy and overthrow the use of imperfect empiric, 
 or c rule-of-thumb ' methods often largely employed in 
 alkali works, it indicates a more scientific method, it will 
 accomplish some good. 
 
 Products of the Trade : Iron, copper, silver, gold, 
 sulphuric and hydrochloric acids, bleaching powder, po- 
 tassic chlorate, calcic chloride, sulphate of soda, caustic 
 soda, sodic carbonate and bicarbonate, sulphur, sulphat^ 
 of copper, hyposulphite of sodium, phosphate of sodium, 
 and Epsom salts. 
 
 Waste Products : Part of the hydrochloric acid as 
 chloride of calcium, all the lime or nearly so, part of the 
 sulphur. 
 
 Regenerated Products : Nitre (partly), manganese 
 and part of the sulphur. 
 
 The introduction of recent improvements in the alkali 
 trade was attended with much opposition from manufac- 
 turers themselves. 
 
SCHEME OF THE ALKALI TRADE AS NOW WORKED. 
 
 Scheme of the Alkali Trade as now worked. 
 
 Pyrites with nitre and air. 
 I I 
 
 
 
 1 
 
 
 
 Nitre regenerated. 
 
 Burnt ore. 
 1 1 
 
 Sulphuric acid. 
 1 1 
 
 I 
 
 
 
 
 Iron. 
 
 Copper. 
 
 Silver and gold. 
 
 Sulphuric acid and salt. Epsom salts. 
 
 I | 
 
 | 
 
 Hydrochloric acid. Sulphate of soda. 
 
 II- II 
 
 I I 
 
 Acid -f manganese ores. 
 
 I I 
 
 I! 
 
 Chlorine. Manganese liquors. 
 
 II 
 
 j III I 
 
 Bleaching . Bleaching Potassic Calcic Manganese Calcic 
 liquor. powder, chlorate, chloride, regenerated, chloride. 
 
 Salt cake with coal and limestone. 
 I 1 
 
 Caustic sc da. Alkali waste. Soda carbonates. 
 
 Sulphur regenerated. Lime lost. 
 
 However strange at first sight it may seem, that 
 manufacturers should so stand in their own light, it is not 
 so inexplicable if we bear in mind that they were un- 
 scientific, and, moreover, it must be admitted that there 
 is good reason why they should be chary of adopting 
 new processes until the strongest evidence is forthcoming 
 
8 THE ALKALI TRADE. 
 
 that the new processes give better results than the old 
 ones ; for while, however good the improvements may 
 be, there is always the greater possibility at such times 
 than at others, that the improvements should themselves 
 be improved upon ; and every change of plant means, 
 for the time at least, the sacrifice of so much capital. 
 
 It is gratifying, however, to find that many manufac- 
 turers are now well-known scientific men ; to the truth 
 of this assertion the names of Deacon, Pattinson, Young, 
 Scheurer Kestner and others testify most fully. But it is 
 to be deplored, perhaps, that so much scientific ignorance 
 should exist as is knoivn to exist among many managers 
 and the second-rate chemists often employed at alkali 
 works. These men often boast loudly of their rule-of- 
 thumb methods of working, when those methods are 
 known to be unreliable and therefore worse than useless, 
 inasmuch as they mislead. Of course, when a process 
 becomes familiar to those w r orking it, it is often possible 
 to adopt methods of testing certain products in an abbre- 
 viated way, and so save time and trouble, but there can 
 be no doubt that many of these methods at present 
 largely used are not reliable, and their use should there- 
 fore be discontinued. We refer, for instance, to the 
 estimation of nitrous compounds in oil of vitriol by simple 
 dilution with water; the determination of the temperature 
 of vat liquor by the hand alone, etc. In short, when it 
 is recognised that the chemist's duty in an alkali works 
 consists in the examination and analysis of materials con- 
 sumed, and products manufactured, and so forth, it be- 
 comes evident that his chemical ability should be such 
 as to enable him to accomplish these things in a reliable 
 manner ; and also sufficient to enable him to trace any 
 
THE USE OF CHEMICAL KNOWLEDGE. 9 
 
 loss in a manufacturing process to its source, or to detect 
 any tampering of the materials by the workmen. 
 
 Thus, suppose the production of ' caustic ' in a soda 
 works to bo below the average, then by the analysis of 
 the successive intermediate products, as the salt cake 
 produced in the pots, the vat liquors and so on, he 
 should be able, generally, to discover the source of the 
 loss. In the case under consideration, this might arise 
 from the employment of c salt cake' (sodic sulphate) 
 below average strength, or from the ' balls ' (crude sodic 
 carbonate) being ' burned ' or ' green,' or from imperfect 
 washing of the lime mud from the causticiser, etc. 
 
 To any one acquainted with the status of chemical 
 science in alkali works, the foregoing remarks will not be 
 matter for surprise. Thus, quite recently, the author of 
 a paper on caustic soda, alluded to laboratory work as a 
 4 kind of out-at-elbows trade ' and actually stated his 
 opinion that ' a manager can be too much of a chemist.' 
 To this we must strongly object, for it is absurd to sup- 
 pose that because a manager may be likewise a good 
 chemist, he will be misguided by his knowledge in at- 
 tempting more than reasonable 'maximum productions'; 
 on the other hand, his chemical knowledge will serve him 
 as a rudder serves a boat, namely, as a guide by which 
 to obtain a certain result, without loss of time or labour. 
 
 Chemical industry is just emerging from ignorance 
 and prejudice, and any attempt to return to that state 
 should therefore be opposed. For, as Parkes tells us in 
 his ' Chemical Essays,' it is not so many years ago ' that 
 Mr. Steer, a very large aquafortis maker at Birstall, near 
 Leeds, was for long accustomed to lay his glass retorts in 
 a shallow rivulet which ran through his fields, where, in a 
 
 ?T Of THE 
 Tfff TTTWB 
 
10 THE ALKALI TRADE. 
 
 few weeks, the indurated salt was dissolved and washed 
 away in the water.' In short, industrial chemistry has yet 
 much to attain, as is shown by its history, by the exist- 
 ence of the Alkali Acts, and by the mountains of alkali 
 waste that stagnate the atmosphere for miles round the 
 districts where alkali works exist. But, at the same 
 time, these things demonstrate to us what chemical 
 science, aided by engineering, has done for the alkali 
 trade of Great Britain. We cannot do better than con- 
 clude this chapter with some observations due to Dr. 
 Lunge, who, in a recent address to the Tyne Chemical 
 Society, stated that one of the largest works in Germany 
 employs six chemists, at from 300/. to 400/. per annum, 
 and in addition retains the services of a chemist of repu- 
 tation, exclusively for theoretical work in the laboratory, 
 Sit a salary of nearly 2,000/. per annum. This wise 
 conduct gives rise to happy results, as is exemplified (to 
 those who are conversant with the development of the 
 soda trade in Germany) by the following figures : 
 
 From 1867 to 1872, the German production of sul- 
 phuric acid increased from 57,825 tons to 84,264 tons ; 
 sulphate of sodium from 35,767 to 51,618 tons; and 
 calcined soda ash from 26,250 to 36,227 tons. 
 
FORMATION OF NATIVE SULPHUR. 11 
 
 CHAPTER II. 
 
 PYRITES, SULPHUR AND NITRE, AND THE HISTORY OF THE 
 MANUFACTURE OF SULPHURIC ACID TO 1840. 
 
 BEFORE proceeding to sketch the process employed in the 
 manufacture of sulphuric acid, it will be well if we learn 
 something about the materials consumed, viz., the pyrites 
 or sulphur, and soda nitre. Although, as will be presently 
 seen, the use of (Sicilian) sulphur for making sulphuric 
 acid, has been abandoned, yet, as in the future it may 
 again be used for that purpose, and as in past years 
 it alone was used, it will be of some interest to first 
 describe it, 
 
 Sulphur occurs in volcanic districts, as Toscana and 
 Naples, in great abundance ; and it has been suggested 
 that much of it has been formed as met with, by the re- 
 action that is known to take place between sulphurous 
 anhydride and hydrosulphuric acid. 
 
 2H 2 S+ S0 2 =S 3 + 2H 2 O. 
 
 These gases escape through the furnaroles, and by 
 their mutual reaction give rise to sulphur. This supposi- 
 tion derives some support from the fact that alkali waste, 
 after exposure some time to atmospheric influences, often 
 contains free sulphur, doubtless derived by a similar de- 
 composition, arising from the action of acids upon sul- 
 phides and hyposulphites of calcium. Most of the sulphur 
 originally consumed in the sulphuric acid manufacture 
 
12 THE ALKALI TEADE. 
 
 came from Sicily, no less than' 1,164,099 cwt. being im- 
 ported in 1859, as against 333,731 cwt. imported in 
 1842 (Eichardson and Watts). Sulphur works, however, 
 existed at Walker-on-Tyne, from 1800 to 1822, about 
 twenty tons of roll and flour sulphur being made annually, 
 
 The following figures, showing the sulphur exported 
 from Sicily in the years 1853 to 1860, are taken from the 
 Beport by the Juries of the Exhibition of 1862 : ' In 
 1853 there were exported from Sicily 97,268 tons ; in 
 1854, 111,993; in 1855, 101,393; in 1856, 121,550; 
 in 1857, 125,987; in 1858, 163,629; in 1859, 152,487; 
 in 1860, there were exported 137,745 tons. 
 
 It will be observed that the exportation has not fallen 
 off, as might have been expected, when it was no longer 
 used for making acid, but this is explained by an in- 
 creased demand for gunpowder, and in the other various 
 applications of sulphur. 
 
 Vast sulphur deposits occur also in Iceland, and in a 
 recently published paper, Professor Gesner states, that in 
 the Island of Saba occur the largest, and certainly the 
 richest and most accessible deposits of sulphur in the 
 world. These masses of gypsum, bearing sulphur, con- 
 tain as much as 60 per cent, sulphur, as is seen in the 
 analyses furnished by Mr. G. G. Black well. Sulphur, 
 75*81 to 80'57 per cent. ; silicate and sulphate of lime, 
 14-90 to 20-56 per cent. ; water, 3'63 to 4"53 per cent. 
 
 Sulphur is extracted from the mineral matters with 
 which it is associated by fusion and distillation. When 
 Sicilian sulphur was no longer available through the in- 
 creased price placed on it, which was the effect of a grant 
 of monopoly by the King of Sicily (of which we shall 
 speak further hereafter), manufacturers had to seek other 
 
SULPHUR FROM GYPSUM. 13 
 
 sources. And so great was the industry in this direction, 
 that Liebig in his ' Letters ' tells us, that during the exis- 
 tence of the monopoly of sulphur, no less than 150 
 patents were taken out for the production of sulphur or 
 sulphuric acid from gypsum. 
 
 One of these attempts consisted in exposing gypsum 
 to a high temperature in the presence of silica, by which 
 operation silicate of calcium is formed and sulphurous 
 acid and oxygen evolved. Thus 
 
 CaS0 4 + Si0 2 =CaSi0 3 + S0 2 + 0, 
 
 but this reaction takes place but to a limited extent, even 
 at the highest temperatures. Another process which was 
 suggested, consisted in the decomposition of gypsum by 
 hydrochloric acid, giving chloride of calcium, water, sul- 
 phurous acid, and oxygen. Thus 
 
 CaS0 4 + 2HC1= CaCl 2 + H 2 + S0 2 + ; 
 
 but this process was likewise attended by insurmountable 
 difficulties, and of course in these days one could not for 
 a moment entertain the idea of using hydrochloric acid 
 (in such a manner as to afford no way of recovery), for 
 making sulphuric acid. More reasonable were the pro- 
 posals and attempts to reduce gypsum by coal to sulphide. 
 Thus 
 
 and to decompose the sulphide of calcium into carbonate 
 and hydrosulphuric acid, by means of carbonic acid and 
 steam. Thus 
 
 CaS + C0 2 + H 2 0=CaC0 3 + H 2 S. 
 
 The H 2 S to be then burnt into sulphurous acid ready for 
 use in the chamber. This process was devised by Mr. 
 Gossage, but in practice it did not work well. 
 
14 THE ALKALI TEADE. 
 
 Without pausing to consider more failures (for they 
 were various and many), we will pass on at once to con- 
 sider the use of pyrites, which were destined to fill the 
 place which had been occupied by sulphur. 
 
 Long before this time, pyrites had been used as a 
 source of sulphur in Germany, and in Nordhausen for 
 centuries, in making the famous fuming acid of that name, 
 by a process of dry distillation. MM. Ferret and Son, of 
 Chessy, were the first to successfully use pyrites for the 
 manufacture of sulphuric acid (1833) ; but it was not till 
 five years later, viz., at the date of the grant of the sul- 
 phur-monopoly by the King of Sicily, that its use was 
 introduced into Great Britain on a large scale. At first, 
 our supply was furnished from our own mines in Corn- 
 wall and Ireland, but the demand soon spread to foreign 
 countries, especially when processes were devised for ex- 
 tracting the copper and rare metals from the burnt ores. 
 For, previous to that time, ores free from copper only 
 were employed. So great now is the importation of 
 pyrites that 9-10ths of the sulphuric acid made in England 
 in 1874 were obtained from imported pyrites (Dr. Lunge). 
 These were chiefly derived from Spain, Portugal and 
 Norway. 
 
 The table given at the head of the following page, 
 showing the percentages of sulphur in various ores, has 
 been compiled from a table in Eichardson and Watts' 
 ' Technology ' (vol. i., part iii.), and from analyses furnished 
 by the authors of various papers, read before the New- 
 castle-on-Tyne Chemical Society, etc. 
 
 As a general statement relative to pyrites, it may be said 
 that those now in use contain from 1 to 3 and 4 per cent, 
 copper, and from O f O to 2 per cent, of arsenic. The pre- 
 
COMPOSITION OF PYRITES. 
 
 15 
 
 Constitu- 
 ents 
 
 First 
 Norwe- 
 gian 
 
 Second 
 
 Norwe- 
 gian 
 
 Mason's 
 
 Belgian 
 
 Tuscan 
 
 Westphalia 
 
 Spa- 
 nish 
 
 Cornish 
 
 Irish 
 
 Sulphur 
 
 46-15 
 
 38-17 
 
 47-80 
 
 45-60 
 
 48-4 
 
 
 
 45-2 
 
 24-01 
 and 
 34-88 
 
 34-67 
 
 and 
 42-12 
 
 Iron 
 Copper . 
 Zinc 
 
 Arsenic 
 
 42-20 
 1-20 
 2-10 
 
 32-80 
 1-10 
 2-32 
 
 trace 
 
 42-88 
 2-26 
 
 o-io 
 
 0-28 
 
 38-52 
 
 6-00 
 trace j 
 
 0-943 
 
 (H.A.Smith) 
 
 1-878 
 (H.A.Smith,) 
 
 
 
 
 CaC0 3 . 
 CaS0 4 . 
 MgC0 3 . 
 Insoluble 
 Moisture 
 
 2-55 
 
 trace 
 
 3-20 
 0-40 
 
 11-90 
 
 1-08 
 12-20 
 0-25 
 
 0-18 
 
 2-94 
 0-95 
 
 0-11 
 
 9-00 
 0-36 
 
 -> 
 
 
 
 ( 
 
 r 
 
 Claphai 
 
 -^ 
 n.) 
 
 Total . 
 
 99-80 
 
 99-82 
 
 99-39 
 
 99-59 
 
 Most suitable ores (J. McCulloch). 
 
 sence of much calcic carbonate militates against the per- 
 fect burning of the sulphur, by the formation of sulphate 
 of calcium. The arsenic which is often found in commer- 
 cial sulphuric acid is derived from the pyrites used. As 
 illustrative of this, and of the fact that this arsenic present 
 in pyrites often finds its way into other products of the 
 alkali trade, we adjoin the following table taken from a 
 paper by Mr. H. A. Smith, read before the Manchester 
 Literary and Philosophical Society. 
 
 Substance 
 
 No. of 
 Analyses 
 
 Per cent, as 
 found 
 
 Pyrites before burning (hard Norwegian) . 
 
 8 
 
 1-649 
 
 after .... 
 
 4 
 
 0-465 
 
 Sulphuric acid ..... 
 
 15 
 
 1-051 
 
 Deposit in flue from kiln .... 
 
 4 
 
 46-360 
 
 Deposit on bottom of chamber . 
 
 5 
 
 1-857 
 
 Hydrochloric acid ..... 
 
 8 
 
 0-691 
 
 Sulphate of soda ..... 
 
 15 
 
 0-029 
 
 Soda waste ...... 
 
 6 
 
 0-422 
 
 Carbonate of soda ..... 
 
 12 
 
 
 
 Recovered sulphur (by Mond's process be- 
 
 
 
 fore purification was introduced) . 
 
 4 
 
 0-700 
 
 Mond's sulphur, latest methods 
 
 2 
 
 
 
 
16 THE ALKALI TRADE. 
 
 The presence of arsenic in sulphuric acid is likely to 
 lead to much evil, when that acid is used for tinning iron, 
 inasmuch as it is deposited in specific places which then 
 refuse to take the tin. Moreover, from the residual ore, 
 after burning, it finds its way into the copper, which is 
 obtained therefrom in the manner to be shown, and this 
 renders the copper brittle and greatly reduces its market 
 value. We shall, therefore, have to discuss presently 
 various proposals and methods for isolating this arsenic at 
 certain stages. 
 
 Mr. E. Calvert Clapham, in a paper from which we 
 shall again quote, gives the total consumption of pyrites 
 of all kinds in the United Kingdom for 1869 as 400,000 
 tons. 
 
 Tons. 
 
 From Norway 63,091 
 
 Holland 13,983 
 
 Portugal 140,805 
 
 Spain ...... 99,648 
 
 Other parts . . . . . 2,420 
 
 Total 319,947 
 
 Produced in Ireland 56,291 
 
 Cornwall and elsewhere .... 19,658 
 
 Total 75,949 
 
 Of this quantity 265,453 tons were cupreous pyrites. 
 
 Tons. 
 
 From Norway 25,000 
 
 Portugal 140,805 
 
 Spain 99,648 
 
 According to M. F. Kuhlmann (jun.), mines of pyrites 
 were discovered in the island of Kauno, off Norway, in 
 1865, by M. Defrance. This consists of sulphide of iron 
 and sulphide of copper, furrowed with blende. The 
 average proportion of sulphur contained, is 45 per cent., 
 with 3 per cent, copper ; though certain parts contain 
 
ARTIFICIAL PYRITES. 17 
 
 from 12 to 14 per cent, copper. It is entirely free from 
 arsenic, which enhances its value, while it contains but 
 very small quantities of silver and gold. 
 
 Pyrites are also found in Italy containing a notable 
 proportion of Eammelsbergite (NiAs). In some sorts of 
 Italian pyrites there is as much as 3*75 per cent, nickel, 
 and possibly this may at some future time be as profitably 
 extracted, as the copper is now from Spanish pyrites. 
 
 Eecently Martin, of Asnieres, has proposed to replace 
 pyrites by an. artificial sulphide of iron, to be made by 
 fluxing sulphate of lime, ferric oxide and charcoal, in the 
 following proportions : Sulphate of lime, 1,700 ; per- 
 oxide of iron, 1,000 ; charcoal, 500. 
 
 Another source of sulphur is the sulphurised ferric 
 oxide obtained by Hill's process for abstracting the sul- 
 phuretted hydrogen from coal-gas, and otherwise purify- 
 ing it. This process consists in passing the gas over a 
 mixture of hydrated ferric oxide and sawdust. There is 
 thus obtained protosulphide of iron and free sulphur. 
 By atmospheric oxidation the iron peroxide is regenerated 
 or revivified, and the remaining sulphur liberated from its 
 combination, when the product is again ready to purify 
 more gas. These operations are repeated over and over 
 again, until the product contains as much as 40 per cent, 
 sulphur, and 1 ton of the mixture is stated to yield 1^ ton 
 of hydrated sulphuric acid. For burning it, however, a 
 special form of kiln is requisite. 
 
 Such a product as that just described is also obtained 
 in the working of a process (to be explained in a future 
 place) for making soda, and unless it proved more desir- 
 able to extract the sulphur in the pure state, by dissolving 
 the ferric oxide in hydrochloric acid, it might pro- 
 
18 
 
 THE ALKALI TRADE. 
 
 bably be well applied for the manufacture of sulphuric 
 acid. It will be understood that the process to which we 
 here refer is not actually in use, although it holds out 
 some promise of success. 
 
 The consumption of pyrites in France has risen during 
 the last ten years from an annual amount of 90,000 tons 
 to 180,000 tons, and in England during the same period, 
 from 180,000 to 520,000 tons. It is calculated that the 
 total amount of pyrites in France is equal to a century's 
 consumption. The pyrites from the St. Bel district con- 
 tain from 46 to 53 per cent, of sulphur. 
 
 Soda nitre (nitrate of sodium) occurs in almost un- 
 limited quantity in South America, especially in the district 
 of Atacame, in Peru, where it is found from 0*6 to 1*0 
 metre below the surface of the soil. It is used in prefer- 
 ence to potassic nitrate, because it is not only cheaper but 
 yields 9 per cent, more nitric acid. The chief quantities 
 consumed in the alkali trade are in the manufacture of 
 sulphuric acid, and for the oxidation of sulphides, etc., in 
 the caustic pots, of which more anon. The commercial 
 name for sodic nitrate is caliche. 
 
 The following analyses are by Dr. A. T. Machat- 
 tie, F.C.S. : 
 
 Analyses of caliche 
 
 No. 1. White 
 caliche 
 
 No. 2. Brown 
 caliche 
 
 Sodium nitrate 
 
 70-62 
 
 6097 
 
 Sodium iodate 
 
 1-90 
 
 0-73 
 
 Sodium chloride . 
 
 22-39 
 
 16-85 
 
 Sodium sulphate . 
 
 1-80 
 
 4-56 
 
 Calcium sulphate . 
 
 0-87 
 
 1-31 
 
 Magnesium sulphate 
 
 0-51 
 
 5-88 
 
 Insoluble matter . 
 
 0-92 
 
 4-06 
 
 Water 
 
 0-99 
 
 5-64 
 
 
 100-00 
 
 100-00 
 
NATIVE NITRATE OF SODIUM. 
 
 19 
 
 From the commercial caliche the purer soda nitre is 
 obtained by crushing the mineral and recrystallising it 
 from water, whereby a product results containing from 
 95 to 96 per cent, of pure sodium nitrate. The mother 
 liquors are worked for iodine, but the process is a secret 
 one. 
 
 The following further information regarding the nitrate 
 of soda trade of South America is furnished by M. V. 
 L'Olivier. He states that the nitre beds were discovered 
 in 1821 by Mariano de Eivero, but were not worked till 
 1831. The nitre is from 0'3 to 2 metres thick, and forms 
 irregular masses, alternating with beds of common salt 
 and borate of lime at the height of about 1,000 metres, 
 and extending from 19 to 23'5 south latitude. He 
 considers the presence of the nitre to result from the 
 evaporation of once-present salt lakes. It is generally 
 found covered by costra, which is a harder saline deposit, 
 and has its own value. L'OHvier found samples of nitre 
 and one of costra from the basin of the Loa to have the 
 following compositions : 
 
 Constituents 
 
 Nitre 
 
 Costra 
 
 
 (1.) >) 
 
 
 Nitrate of soda 
 
 51-50 
 
 49-05 
 
 18-60 
 
 Sulphate of soda 
 
 8-09 
 
 9-02 
 
 16-64 
 
 Chloride of sodium 
 
 22-08 
 
 28-95 
 
 33-80 
 
 Chloride of potassium 
 Chloride of magnesium 
 
 8-55 
 0-43 
 
 4-57 
 1-25 
 
 2-44 
 1-62 
 
 Carbonate of lime 
 
 0-12 
 
 0-15 
 
 0-09 
 
 Silica and oxide of iron 
 
 0-90 
 
 2-80 
 
 3-00 
 
 Iodide of sodium 
 
 sometimes traces 
 
 traces 
 
 
 
 Insoluble matter 
 
 6-00 
 
 3-18 
 
 20-10 
 
 Some samples of nitre, however, contain from 60 to 
 70 per cent, of nitrate of sodium, and sometimes even it is 
 
 c 2 
 
20 THE ALKALI TRADE. 
 
 found pure and crystalline. The export duties which the 
 Peruvian Government lay upon it are imposed with a 
 view of preventing its competition with guano. These 
 restrictions will tend to transfer the nitrate of soda in- 
 dustry to the basin of the Loa. 
 
 It is calculated that the 131 establishments in Peru 
 could produce 780,000 tons per annum, although the ac- 
 tual production has never exceeded 300,000 tons. Of this 
 article, during the first eight months of 1875 no less than 
 44,840 tons were imported into France. 
 
 Historical Notes on the Manufacture of Sulphuric 
 Acid. Sulphuric acid is first mentioned in the writings of 
 Basil Valentine, of Erfurt, according to the statement of 
 most historians. But Mr. Eodwell in his classical work 
 on ; The Birth of Chemistry,' gives data from which we 
 conclude it was known long before the time of Basil 
 Valentine. Sulphur itself was well known and used in the 
 making of matches in the time of Pliny ; and apparently 
 it was also burnt in a current of air and the sulphurous 
 acid employed for bleaching purposes. Pyrites were used 
 at this time for striking fire with steel in order to kindle 
 timber, hence the origin of the name. Geber, an Arab of 
 the eighth century, obtained sulphuric acid by distilling 
 alum ; but it was reserved for Andrew Libavius (died 
 1616) to prove that the acid procured by distilling alum 
 or sulphate of iron is the same as that prepared by burn- 
 ing sulphur with saltpetre. Basil Valentine (born 1394), 
 was well acquainted with the preparation of sulphuric 
 acid, 'and used it for various purposes of dissolution. He 
 obtained fuming sulphuric acid by distilling green vitriol 
 after the manner still practised near Nordhausen. Mayow 
 (born 1645, died 1679) considered sulphuric acid to consist 
 
HISTORICAL NOTES ON SULPHURIC ACID. 21 
 
 of c nitre air united with sulphur,' meaning, of course, oxy- 
 gen and sulphur. Under the phlogiston theory, sulphuric 
 acid was sulphur which had lost phlogiston, and therefore 
 its calx had become heavier in our language it had taken 
 up oxygen. Although Paracelsus, the Swiss alchemist, 
 who died in 1541, was acquainted also with sulphuric 
 acid, it was not till 1570, when Gerard Dornseus pub- 
 lished his work, that anything like a correct account of 
 it was given. 
 
 Sulphuric acid is found in many springs having con- 
 nection with volcanoes, and is doubtless derived by com- 
 bustion of the sulphur which exists so largely in those 
 districts, together with slow oxidation. 
 
 The English makers originally prepared their acid by 
 the distillation of green vitriol in earthen vessels, known 
 as ' long necks,' placed within a reverberatory furnace, and 
 connected with receivers of glass by means of lute. In 
 this way fifty or more ' long necks ' were at work in one 
 furnace. ' Copperas works had existed in England from 
 an early date ; in 1748 they began at Hartley, and in 
 1797 at Walker. The copperas, after being dried, was 
 placed in brick ovens, to which a strong heat was applied ; 
 the acid distilled off and was condensed, and formed an 
 impure oil of vitriol. If 1 ton of copperas produced 
 1J> cwt. of acid, it was considered a fair result. The price 
 was 2s. per Ib. or 220/. per ton. The present price being 
 only 61. per ton.' (E. Calvert Clapham, 'Account of Soda 
 Manufacture on the Tyne.') 
 
 But this process of manufacture, owing to the intense 
 heat required and the ' wear and tear ' of the stills, gave 
 way to the use of sulphur and nitre (1736), which were 
 burnt in very large glass globes and the product concen- 
 
22 THE ALKALI TRADE. 
 
 trated by boiling in glass retorts or other vessels. This 
 method of making sulphuric acid is attributed by Fourcroy 
 to Lefevre and Lemery ; but in this country it was first 
 adopted by Dr. Ward, who called his product ' oil of 
 vitriol made by the bell,' and which was sold at Is. Qd. to 
 2s. Qd. per Ib. 
 
 It was about the year 1746 that Dr. Koebuck, of 
 Birmingham, in conjunction with his partner, Mr. Samuel 
 Garbett, erected the first leaden chamber, but the use of 
 the acid so made was confined almost exclusively to the 
 neighbourhood, owing to the absence of canals and the 
 danger of land carriage. It was consumed in the re- 
 covery of gold and silver from gilt and plated goods, for 
 dissolving copper and making Eoman vitriol. But three 
 years later, these same men erected other works at Pres- 
 tonpans, on the eastern coast of Scotland, and here they 
 made experiments as to the use of sulphuric acid in 
 whitening linen cloth. These experiments were published 
 by Dr. Home, of Edinburgh, and led to the abolition of 
 sour milk for bleaching purposes. Thus, a greater de- 
 mand was created ; and, in short, not only did they supply 
 the United Kingdom, but also exported large quantities. 
 In 1790 England exported 2,000 tons. 
 
 From time to time the size and form of the leaden 
 chambers which were erected varied. In 1772, Kings- 
 cote and Walker's Works, at Battersea, consisted of 
 seventy-one circular vessels, each of 6 feet diameter and 
 6 feet high. Previous to this, chambers of 6 feet and 
 10 feet square had been in use. 
 
 The introduction of chlorine as a bleaching agent, in 
 1788, gave an impulse of a great character to the manu- 
 facture of sulphuric acid ; the working capacity of the 
 
SULPHURIC ACID FROM SULPHUR. 23 
 
 chambers was greatly increased, and as the result of 
 observation, the height of the chambers was decreased, 
 until the average dimensions may be stated to have been 
 60 to 80 feet long, 10 to 14 feet broad, and 6 to 8 feet 
 high. This height contrasts strongly with a large cham- 
 ber previously in use in Lancashire, of 120 feet x 40 
 x 20 feet high, and of capacity 96,000 cubic feet. The 
 advantages of the sized chambers which now came into 
 use are obvious, as they admitted of being built on a 
 frame-work of timber, so that the bottoms could be 
 easily repaired, the effects of gravitation secured, and 
 the space below economised. 
 
 In the early days of the manufacture, 7 or , 8 Ib. of 
 sulphur, carefully mixed with 1 Ib. of crude saltpetre, 
 constituted the proportions employed, and of this mixture 
 1 Ib. was considered to feed 300 cubic feet of chamber- 
 air. This mixture placed upon plates of iron or lead, 
 and supported on stands of lead, was burnt within the 
 chamber, a foot or two 'above the surface of the water, 
 being ignited by a hot iron. The next improvement was 
 the introduction of a distinct apartment for burning the 
 sulphur. Mr. Parkes, in his ' Chemical Essays,' states that 
 from 1 Ib. of sulphur by this method he obtained 2f Ib. 
 of sulphuric acid of specific gravity 1*848. The furnace 
 consisted of a round oven of firebricks of 4 to 5 feet 
 diameter, and having the floor 2 feet from the ground, 
 and a roof of brick, the crown of which was arched, 
 and at its highest elevation 2 feet from floor. The air 
 admitted was regulated by a small sliding door of tin 
 plate, moving in the primary door of sheet iron. The 
 sulphurous acid was conveyed away through the roof by 
 an iron pipe of 12 inches diameter. 
 
24 THE ALKALI TRADE. 
 
 In the next phase of the manufacture the crude 
 sulphur was worked with water into a paste, and the 
 bricks, of about 20 Ib. weight, dried on the top of the 
 furnace. Contemporary with this improvement was 
 the introduction of saltpetre pots, the saltpetre used 
 being in the proportion of a tenth of the sulphur em- 
 ployed, with enough sulphuric acid to effect a proper 
 decomposition. At the same time the gases were cooled 
 by passage through water contained in a leaden vessel 
 from which the water dropped into the chamber. In 
 1828 Kestner, of Thann, introduced in this country the 
 use of steam in the chamber, and about the same time 
 the ' drop tube ' for testing the strength of the acid came 
 into use. Up to this time the gases issuing from the 
 chamber were passed into the chimney of the works. 
 
 The next great change in the history of the sulphuric 
 acid manufacture was the substitution of pyrites for 
 sulphur. It was in 1838 that the King of Naples granted 
 a monopoly of the Sicilian sulphur trade to Messrs. Taix 
 and Co., of Marseilles, in consequence of which the price 
 rose from 5/. to 14:1. per ton (Gossage). Eecourse was 
 therefore had to pyrites, and Mr. Thomas Farmer, in 
 1839, was the first in this country to make use of this 
 substance, although it had been previously used in 
 France. Moreover, a Mr. Hill, of Deptford, is said to 
 have employed ore instead of sulphur in 1818. Spanish 
 pyrites were first used in 1856, Belgian pyrites in 1858, 
 Westphalian in 1861, and Norwegian in the same year. 
 
 These historical notes have brought us to the present 
 mode of making sulphuric acid ; here, therefore, we shall 
 not enter into improvements which have been effected 
 since 1840, but shall proceed to study them in treating 
 
PREPARATION OF SULPHURIC ANHYDRIDE. 25 
 
 of the manufacture as at present carried on in this 
 country, in our next chapter. But there is just one 
 point which may conveniently be noticed here. Of 
 late there has been a demand in the aniline trade for very 
 strong sulphuric acid, and Nordhausen acid has been im- 
 ported to meet this demand. 
 
 Drs. Messel and Squire having occasion to take cog- 
 nisance of this, turned their attention to the manufacture 
 of sulphuric anhydride, and successfully worked out a 
 process which they described in a paper recently read 
 before the Chemical Society (April 20, 1876). Sulphuric 
 acid of commerce is boiled in a platinum still, and the 
 vapour is passed through a white-hot platinum tube ; in 
 this way it is almost completely decomposed into water, 
 oxygen and sulphurous anhydride. From the plantinum 
 tube the mixed gases are led through a leaden worm 
 cooled by water, whereby the greater portion of the 
 water contained in them is condensed, and thence up a 
 coke scrubber filled with coke, where the gases are 
 thoroughly dehydrated by meeting a current of descend- 
 ing concentrated acid. The dry mixture of sulphurous 
 anhydride and oxygen is now passed through platinum 
 tubes, which are heated to low redness by the waste 
 heat used for the decomposer. These platinum tubes 
 contain fragments of platinised pumice, which effect the 
 re-combination of the gases, and the product is condensed 
 in a series of Woulffe's bottles. The platinum tubes, it 
 may be remarked, are heated in an ordinary Hofmann's 
 combustion furnace of a large size. 
 
 This process may thus be represented : 
 
 H 2 S0 4 +Heat=S0 2 
 and S0 2 + =S0 3 . 
 
26 THE ALKALI TRADE. 
 
 CHAPTEE III. 
 
 MANUFACTURE OF SULPHURIC ACID. 
 
 IN the present chapter we propose briefly to indicate, in 
 the first place, the rationale of the various processes en- 
 tering into this manufacture, before we proceed to study 
 each operation in detail. 
 
 The pyrites (iron and cuprous iron pyrites) are broken 
 up into lumps about the size of pebbles, and are then 
 roasted in a current of air, in an arrangement designated 
 the ' burner.' By absorption of oxygen from the air, the 
 iron becomes ferric oxide, while sulphurous anhydride is 
 formed; thus 
 
 2FeS 2 + Oi ! =Fe 2 3 + 4SO 2 . 
 
 The gas passes into a flue, where it mixes with the 
 vapour of nitric acid, generated in a ' nitre-pot,' from a 
 mixture of sulphuric acid and nitrate of sodium 
 2NaN0 3 + H 2 S0 4 =Na 2 S0 4 + 2HN0 3 . 
 
 The mixed gases now pass on to what is called ' the 
 chamber,' where, aided by the presence of steam, com- 
 bination is effected, and sulphuric acid formed. The 
 exact processes occurring in the chamber have been 
 much debated ; here we shall not enter into this discus- 
 sion, but shall represent the process as taking place by 
 virtue of the following reaction : 
 S0 2 f 2HN0 3 =H 2 S0 4 
 
RATIONALE OF SULPHURIC ACID MANUFACTURE. 27 
 
 The sulphuric acid condenses in vesicles and falls to 
 the floor of the chamber, where it is absorbed by water 
 or dilute acid, while the nitric oxide resulting from the 
 reaction indicated, takes up oxygen from the excess of 
 air present, becoming nitric peroxide (N 2 2 + 02 = N 2 4 ), 
 which in its turn fulfils the functions of nitric acid as 
 represented above. Finally, the residual gases from the 
 last chamber (for chambers are worked in series), con- 
 taining the nitric peroxide and all the nitrogen of the air 
 which has been used, pass on to the ' absorbing columns/ 
 which are arrangements which take advantage of the 
 solubility of the oxides of nitrogen in strong sulphuric 
 acid, to effect the removal of such oxides from the mixed 
 gases, while the nitrogen escapes. The absorbing columns 
 are known as ' Gay-Lussac's towers/ 
 
 The sulphuric acid from such towers loaded with the 
 oxides of nitrogen is denitrated by blowing steam 
 through it, and conveying the gases liberated in this way 
 to the chamber ; or, which is much better, the nitric com- 
 pounds are recovered by causing the acid to come in con- 
 tact with the sulphurous anhydride from the burners ; 
 this is effected in what are called ' Glover's towers.' 
 
 The most recent improvement in the manufacture of 
 sulphuric acid, introduced by Dr. Hermann Sprengel, and 
 consisting in the economisation of the steam used in the 
 chamber by the use of water-spray, will be fully de- 
 scribed together with other matters further on ; so also, 
 finally, will be described the manner in which the acid is 
 concentrated to any desired strength. 
 
 The pyrites burners, while they are variously con- 
 structed to meet the requirements of each sort of ore, are 
 all constructed on one principle, which aims at burning 
 
23 THE ALKALI TEADE. 
 
 off the whole of the sulphur with the minimum admission 
 of air. This is a difficult matter to succeed in, because 
 much of the oxygen goes to oxidise the iron from which 
 the sulphur is abstracted, and thus an additional amount 
 of nitrogen is introduced over that quantity, which cor- 
 responds to the oxygen calculated only upon the sulphur. 
 Here and there, even now, is to be found a burner in 
 use, which is of ancient date, and which was improved 
 by Mr. Hunt. It is constructed on the principle of a 
 lime-kiln, where the charge is introduced at the top, arid 
 the burnt residuum withdrawn below. 
 
 Without going through the lists of the various burn- 
 ers which have been in use, or proposed for use, it may 
 be stated that up to a recent period it was usual to burn 
 the pyrites in a series of twelve to twenty of a much 
 smaller character than the form now commonly used. 
 One of the best forms of burner, and one which may be 
 taken as representing the others, was introduced by Mr. 
 Harrison Blair; it consists in one large oven, which is 
 charged once in twelve or twenty-four hours, and is pro- 
 vided with a slit arrangement in the door of the furnace 
 for regulating the amount of air admitted. Its special 
 advantage is the prevention of excessive dilution of the 
 sulphurous anhydride by air, and with its use, a chamber 
 of 25,000 cubic feet capacity is stated to give twenty-one 
 tons of rectified acid weekly, against eleven tons by the 
 ordinary old form of burner. 1 
 
 The amount of pyrites (after crushing in a mill and 
 sifting from the finer portions) constituting a charge 
 
 1 See 'Report on the Recent Progress, etc. of Manufacturing Chemistry,' 
 by Drs. E. Schunck, Angus Smith, and Roscoe. (' British Association Re- 
 port/ 1871.) 
 
PYRITES BURNERS. 
 
 29 
 
 varies somewhat, but 5 cwt. per twenty-four hours per 
 burner is one not uncommonly used. 
 
 For the sketches of an arrangement of pyrites burners 
 (figs. 1 to 3), now largely used in alkali works, and of an 
 
 FIG. 1. 
 
 FIG. 2. 
 
 arrangement of twenty sets of burners, with nitre pots, 
 and gas-conducting pipes, attached for conveying the gas 
 
30 
 
 THE ALKALI TRADE. 
 
 to the chamber (figs. 4 and 5), we are indebted to the 
 courtesy of Messrs. Eobert Daglish and Co. of St. Helen's 
 Iron Foundry, as also for other engravings bearing their 
 
 FIG. 3. 
 
 names. On the faces of the burners are to be seen the 
 charging doors, stirring holes, and the slit arrangement 
 for admitting and regulating the supply of air. The 
 
 FIG. 4. 
 
 charge is withdrawn by tilting the bars upon which it 
 rests, when the burnt pyrites fall to the floor and can 
 
THE TREATMENT OF ' SMALLS.' 
 
 31 
 
 FIG. 5. 
 
 then be raked out. The whole burner is lined internally 
 with firebricks, and near the centre of the roof there 
 is a hole in each, through which the gases escape into 
 a flue, running between the first roof of the burners and 
 the second true roof. The usual size of the burner may 
 be stated as about 6 feet 6 inches wide and 6 feet deep, 
 as indicated by the burner front. 
 
 It has been stated that the pyrites after crushing are 
 riddled from the dust and smaller fragments before being 
 burnt. This is done in order that the air-passages to the 
 burning pyrites may not become choked, and so prevent 
 the perfect combustion of the sulphur. These powdered 
 fragments of pyrites are designated 
 4 smalls,' and many have been the 
 special furnaces constructed for their 
 combustion. One of the best of these 
 burners was introduced by Mr. Bpence, 
 and employs a hearth of firebrick 
 about 40 feet long by 6 feet wide, 
 fired from below, and fed with air 
 through an opening in the front 1 
 governed by a damper. The material 
 being introduced at the extremity furthest from the fire, 
 is gradually worked up to the hottest parts, and so per- 
 fect combustion is secured. This mode of burning smalls 
 is not largely in use at the present time, and even the 
 plan of making them into bricks with clay (10 per cent.) 
 to be then burnt in the kilns, has given way to a better. 
 When clay was used, it was difficult to get anything like 
 a perfect combustion of the sulphur, while the residual 
 ore presented difficulties in working, and, consequently, 
 degenerated in value. The method of treating ' smalls,' 
 
32 THE ALKALI TRADE. 
 
 now most usually employed, consists in stirring them 
 with water and spreading them out to dry in thin layers 
 on the tops of the furnaces. Oxidation there ensues with 
 the production of a certain amount of sulphate of iron, 
 which serves to bind the particles together, and in this 
 agglutinated form compact masses are obtained which 
 admit of burning in the ordinary kilns. In some works 
 the amount of air admitted into the burners is regulated 
 by controlling the egress of gases from the chambers. 
 At other places Combe's anemometer is employed and 
 fixed in a tube connected with the front of the burner. 
 In any case the gases issuing from the chambers should 
 not contain more than 2 to 3 per cent, oxygen. The 
 residual ore after burning contains generally from 2 
 to 4 per cent, of sulphur, but with smalls the residual 
 sulphur generally exceeds this quantity by 1 or 2 per 
 cent. 
 
 In the burning of pyrites, white fumes are always 
 generated along with the sulphurous anhydride. These 
 fumes consist of sulphuric anhydride (S0 3 ), and have 
 been ascribed as due to the decomposition of sulphate of 
 iron, or to the concourse of the sulphurous anhydride 
 and moisture. 
 
 Wohler long ago showed that by the passage of air and 
 sulphurous acid over freshly formed ferric oxide (Fe 2 3 ), 
 a combination was effected. Eecently A. Scheurer Kest- 
 ner has described experiments, from which he concludes 
 that these white fumes seen in the sulphur kilns, arise 
 from a combination of sulphurous acid and oxygen, 
 effected by means of the residual ferric oxide, which is 
 stated to act as a carrier of the oxygen. 
 
 From the burners the gas passes into a flue which 
 
THE USE OF NITRE POTS. 33 
 
 has been described, where it meets other gas from other 
 burners, and the whole body of gas now passes on to mix 
 with the nitric acid prepared in the nitre pot, which is 
 situated between the burners and the chambers. 
 
 The nitre pots are constructed of cast iron, and vary in 
 size. Those now generally used are larger than those 
 employed in times past, and like the one shown in sketch 
 (fig. 6, kindly supplied by Messrs. Daglish and Co.), are 
 4 feet 8 inches in length, and 1 foot broad. Smaller pots 
 are preferred by some, for the reason that in the action of 
 sulphuric acid on soda nitre (NaN0 3 ) great heat is evolved, 
 and this, together with the heat of the burner gas, often 
 drives off all the nitric acid quite suddenly. It must be 
 
 FIG. 6. 
 
 <' a* . 
 
 understood that in those works where ' Glover towers ' 
 are used for regaining the oxides of nitrogen issuing in 
 gases from the chamber, the nitre pots are only worked 
 at times, just to keep up the average working amount of 
 nitric acid. We shall have more to say about the con- 
 sumption of nitrate of sodium when we come to describe 
 Glover towers, which are now in almost universal use. 
 The quantity of nitre used varies from 3 to 4 or 5 per 
 cent, on the sulphur burnt. From the ' nitre pots ' the 
 gases pass on to the ' chambers' through an iron pipe 20 
 to 30 feet long (for cooling). These chambers are neces- 
 sarily of huge size for three reasons : (1) On account of 
 the large bulk of gases to be dealt with ; (2) because air 
 containing 79 per cent, nitrogen, therefore only contains 
 
 D 
 
34 THE ALKALI TRADE. 
 
 in 100 volumes 21 of oxygen for consumption ; (3) 
 because it is required that the gases in the chamber shall 
 come into intimate mutual contact. The gases are con- 
 ducted into the chambers at one end, and the chambers 
 are supplied with syphon-arrangements and cisterns for 
 carrying off and for storing the acid which is made. 
 
 Chambers are worked in sets of three to five, and it 
 was usual in past times to section off the internal space 
 by partitions of lead attached alternately to the floor and 
 roof. The object of this arrangement was to more effect- 
 ually mix the gases, but as it was found that these 
 pieces of lead soon corroded, the use of them has been 
 discontinued in most places. 
 
 The following are representative dimensions of sul- 
 phuric acid chambers: (1) 75 feet long by 35 feet wide 
 by 35 feet high; (2) 140 feet long by 24 feet 5 inches 
 wide by 19 feet 5 inches high ; (3) 100 feet long by 20 
 feet wide by 18 feet high. No. 3 constitutes a very good 
 working chamber, and with the best advantage 1 cwt. of 
 sulphur can be burnt in twenty-four hours for each 3,000 
 cubic feet of chamber-space. 
 
 There is a deal of divided opinion upon the most 
 suitable-sized chamber to employ, and as to the best 
 working conditions. Mr. H. A. Smith, who seems to 
 have directed much attention to this manufacture, gives 
 as the best form of chamber one of the following dimen- 
 sions : 150 feet long, 25 to 30 feet wide, and 10 to 12 
 feet in height. He points out that the upper part of the 
 chamber is of use principally as a reservoir for the gases, 
 and that little or no reaction takes place at that part. 
 This conclusion is based upon a number of experiments, 
 in which he has estimated the relative amounts of sul- 
 
SULPHURIC ACID CHAMBEES. 35 
 
 phurous acid, sulphuric acid, and nitric acid, at certain 
 stages of the passage of the gases through the chamber, 
 and at heights of from 3 to 15 feet. 
 
 As the action takes place chiefly at the surface of the 
 acid, in starting a chamber it. is better to employ sul- 
 phuric acid on the floor of the chamber than water, to 
 the depth of 2 or 3 inches. As to the quantity of the 
 steam which has to be injected into the chamber, Mr. 
 Smith states that it should increase in proportion to the 
 increase of temperature, but should be less in volume 
 than the combined volumes of the two gases. The tem- 
 perature of the chamber should be about 93 0. (200 
 Fahr.), and the steam is generally injected at a pressure 
 of from 10 to 11 Ib. to the inch. Much steam is obtained 
 in some works by utilising the waste heat from the pyrites 
 kilns ; but presently we shall discuss at some length an 
 improvement which has been effected in reference to the 
 consumption of water (as steam) in the chamber, and, 
 consequently, in reference to the fuel used. 
 
 In building chambers which are to be used, say in 
 sets of five, the first two should be of 7 Ib. lead, and the 
 others about 6 Ib. This is because the first chambers 
 ultimately contain the stronger, and therefore the heaviest 
 acid. Muspratt was of opinion that the acid fluidified in 
 the chamber as soon as formed, and that it then falls 
 like rain to the floor, in which case the sides do not 
 assist in liquefaction. Many manufacturers, endorsing 
 this view, build large chambers accordingly. 
 
 The following working details of six chambers of 
 180 feet long by 21 feet wide and 20 feet high, during 
 
 five years, are taken from an essay by Mr. M ; Culloch : 
 
 (1) Temperature of chambers 160 Fahr. but receiving 
 
 D2 
 
 jf. TKS 
 
36 THE ALKALI TRADE. 
 
 chamber only 90 Fahr. ; (2)28 cubic feet space per pound 
 of sulphur per twenty-four hours, giving an average 
 production of 284 per cent, oil of vitriol on the sulphur 
 consumed in forty burners, but without the employment 
 of Glover towers ; (3) to obtain a good production the 
 ' drops ' from the strong chamber should test 130 to 
 135 T., and from weak chamber about 100 T. ; (4) 
 280 to 290 parts of oil of vitriol of sp. gr. 1-85 on 100 
 parts of sulphur is a good production, theory requiring only 
 306 oil of vitriol of that sp. gr. ; (5) a better return is made 
 on 286 to 294 of acid of sp. gr. 1'846 on 100 of sulphur. 
 
 We have spoken above of chamber ' drops.' These 
 are supplied from an apparatus known as a ' drop tube/ 
 which allows an observer to take the strength of the 
 acid contained in the chamber. Sprengel has invented 
 an apparatus for gauging the depth of liquid on the 
 chamber floor, and for withdrawing a sample of all the 
 heterogeneous layers of liquid for determining the mean 
 specific gravity. This apparatus consists of a graduated 
 tube of glass, provided with a caoutchouc piston. When 
 the acid in the chamber attains a specific gravity of about 
 1-6 it is withdrawn, and either used in that state, or 
 purified, or concentrated. We will now consider the 
 improvement which has been introduced into the sul- 
 phuric acid manufacture quite recently by Dr. Sprengel, 
 and in doing so we shall quote from facts kindly furnished 
 us by that gentleman himself. 
 
 About 1,000 tons in every 2,000 tons of chamber 
 acid consists of water which has once been steam as in- 
 jected into the chamber, and therefore has occupied space, 
 and by its heat expanded the bulk of the gases, a con- 
 dition of things unfavourable to acid making, For it 
 
SPREXGEL'S WATER SPRAY PROCESS. 
 
 37 
 
 may be said that by lowering the temperature of cham- 
 ber-gas a shrinking of its volume is effected, a condition 
 which favours the formation of sulphuric acid. With 
 this knowledge to work upon, Dr. Sprengel has intro- 
 duced into the manufacture a patented process for sub- 
 stituting chamber steam by pulverised or atomised water 
 or spray. This is done by causing some steam to escape 
 from a platinum jet under a pressure of about two atmo- 
 spheres into the centre of a flow of water, as shown in 
 the adjoining sketch (fig. 7). 
 
 Twenty pounds of steam thus convert 80 Ib. of water 
 
 FIG. 7. 
 
 into a cloudlike mist at the rate of about one-third of a 
 ton in twenty-four hours. These jets are placed in the 
 sides of the chamber about 40 feet apart. Where this 
 process has been at work on a large scale (Barking, in 
 Essex), nearly two-thirds of the quantity of coal formerly 
 burned for steam production have been saved, while its 
 
38 THE ALKALI TRADE. 
 
 employment brings about those conditions of temperature 
 and volume of the chamber gases which we have indi- 
 cated as favouring the production of oil of vitriol. There 
 seems to be no doubt that from the very nature of this 
 improvement, and the simple way in which it works, that 
 it will be largely adopted. 
 
 Dr. Sprengel also proposes in his patent to use the 
 spray for effecting the absorption of the lower oxides 
 of nitrogen contained in or escaping from the acid cham- 
 bers ; and he has also patented the use of nitrous sul- 
 phuric acid (as obtained in the Gay-Lussac towers) to be 
 injected into the chambers in the form of spray likewise, 
 so as to utilise the oxides of nitrogen contained therein. 
 This he proposes as a substitute for Glover towers, 
 which, as we shall see below, perform very successfully 
 the same function. 
 
 As may be supposed, many attempts have been made 
 to supersede the costly lead chambers, but they have 
 all failed. The materials that have been proposed as 
 substitutes for lead include stone and earthenware (Ley- 
 land and Deacon), vulcanised indiarubber, slates, and 
 plates of a material consisting of 70 per cent, stoneware 
 powder and 30 per cent, sulphur (Simon) ; gutta percha 
 is much more rapidly destroyed by sulphuric acid than 
 lead. 
 
 With these observations we will now return to 
 consider the treatment of the gases as they issue from 
 the chambers. These gases consist of nitrogen derived 
 from the air, 2 to 3 per cent, oxygen, and all the 
 oxides of nitrogen which have served the purpose of 
 carrying the oxygen of the air to the sulphurous anhy- 
 dride. The oxides of nitrogen were originally generated 
 
GAY-LUSSAC COLUMNS. 39 
 
 as nitric acid from a mixture of soda nitre and sulphuric 
 acid. We have seen that, owing to the restrictions made 
 on the nitre trade by the Peruvian Government, its use 
 forms an item of considerable expense in the manufacture 
 of sulphuric acid. Therefore it is, that many attempts 
 have been made to recover these oxides of nitrogen 
 existing in the gases issuing from the chambers. 
 
 It is more than thirty years ago, since Gay-Lussac 
 proposed to effect this desideratum by the use of strong 
 sulphuric acid, which has the property of absorbing oxides 
 of nitrogen, and this proposal was first carried into effect 
 at the works of St. Gobain. In this way the consump- 
 tion of nitre, which originally amounted to from one- 
 eighth to one- twelfth of the weight of sulphur burnt, was 
 reduced by one-half, or even in some cases by two-thirds 
 that quantity. The ' absorbing columns,' as they are 
 termed, are virtually leaden towers supported on a timber 
 of framework, high and narrow, and packed with lumps of 
 coke about the size of eggs. The vapours from the cham- 
 bers are led into these towers at a point in one side near 
 the bottom, and in their ascent up through the towers 
 they encounter a current of sulphuric acid of 1*76 sp. gr. 
 flowing downwards over the coke. The acid used for this 
 purpose is stored in a cistern over each tower, to where it 
 is pumped by means of a forcing engine. In its descent 
 through the tower the acid absorbs the nitrous compounds 
 and is stored in a reservoir, while the unabsorbed gases 
 pass into the flue and are carried away. It is now neces- 
 sary to recover from, and restore to the chamber, the 
 nitrous compounds dissolved in the acid, and this was 
 done until recently as follows : 
 
 The acid was pumped up to the top of a second 
 
40 THE ALKALI TKADE 
 
 similar tower, after some dilution with water, and here it 
 was allowed to flow in its descent over coke, while it 
 experienced an ascending current of steam which de- 
 prived it of the nitrous compounds, which, along with 
 the steam, passed into the chambers, while the acid, by 
 absorption of water, became considerably diluted (to 1 '615 
 sp. gr.), and flowed off at the bottom ready for concentra- 
 tion. These latter towers are known as ' denitrating 
 columns.' 
 
 They are sometimes constructed as follows : A cast- 
 iron pipe, 9 feet by 3 feet, is lined with lead, and provided 
 with a further lining of half-thick bricks, with pipeclay as 
 mortar. This is set on end and packed with flints, being 
 connected with the chamber by means of a fire-clay pipe, 
 which conveys the nitrous gas issuing from the other end. 
 The nitro-sulphuric acid enters at the top and trickles 
 over the flints, meeting from beneath the steam. The 
 acid is thus reduced from 148 T. to 104 T. and 
 raised from 60 Fahr. to 300 Falir. and on cooling, 
 gives acid of 128 T. containing traces of nitrous com- 
 pounds. Mr. J. McCulloch, working in this way, has 
 published results, from which we gather the following 
 figures : Using 25,000 tons pyrites annually, an average 
 of 3*5 per cent, nitre has been consumed, but the process 
 has the drawback of requiring 3 or 4 tons of coal per 
 twenty-four hours, to boil up as much weak acid as is 
 required to make strong acid to absorb the nitrous com- 
 pounds accompanying the conversion of 12 tons of sulphur 
 into sulphuric acid. 
 
 Notwithstanding these methods of working, in them 
 there are three distinct sources of loss of nitrous com- 
 pounds, amounting in all to about 3 to 6 per cent, of the 
 
GLOVER DEXITRATIXG TOWERS. 41 
 
 soda nitre used : (1) The chamber acid invariably retains 
 some in solution, although its maximum strength does 
 not exceed 1-60 sp. gr. ; (2) a certain amount escapes 
 absorption in the Gay-Lussac towers ; (3) after the deni- 
 tration by steam of the acid from the absorbing columns, 
 a certain amount always remains in the acid. 
 
 Some few years ago Mr. John Glover introduced into 
 the trade an improvement on the plan just described for 
 denitrating acid. Mr. Glover's plan is now in almost 
 universal use, although the steam process is still used at 
 some works. 
 
 This method of denitration is carried out in what are 
 known as 'Glover towers' (10 feet by 6 feet internal dia- 
 meter), which are built of lead, and lined with brick. Up 
 these towers pass all the products of combustion from the 
 pyrites kilns (or burners), and thus enter the tower at a 
 temperature of about 600 or 700 Fahr. The hot gases 
 meet a descending stream of mixed nitro-sulphuric acid 
 from the Gay-Lussac tower, and weak acid from the 
 chambers, thus thoroughly denitrating and at the same 
 time concentrating the whole of the acid to a density 
 of 145 to 150 T. The nitrous compounds given off in 
 the interior of the tower, along with the steam evolved 
 in concentration and sulphurous anhydride, being carried 
 into the chambers. The issuing acid is then taken 
 either to the Gay-Lussac tower to again absorb the nitrous 
 compounds from the chamber-gas, or otherwise used as 
 needed. By the use of this tower the economic value of 
 the Gay-Lussac tower is fully realised, as an abundant 
 supply of strong acid for it is obtained without any ex- 
 penditure for fuel for concentrating the acid. 
 
 The saving of nitre alone, is said by Mr. Glover to be 
 
42 THE ALKALI TRADE. 
 
 at least half to three-quarters of what was formerly used, 
 while a better yield of acid is obtained from the sulphur 
 burned, and an escape of sulphurous anhydride into the 
 atmosphere is prevented. 
 
 Two objections have been urged against Mr. Glover 's 
 process, namely, an alleged danger of the lead or packing 
 giving way, thus necessitating repairs and laying-off 
 chambers, and the reabsorption of nitre in the columns. 
 
 But Mr. Glover has met these objections and refuted 
 them. He states that these objections never exist with 
 * a properly proportioned and worked tower.' He has had 
 a tower in use for five years without interfering with the 
 packing, and after six years the lining is still good. The 
 acid rather contains sulphurous acid than is imperfectly 
 denitrated. The same tower in converting 1,651 tons 
 sulphur (from Norwegian pyrites) required 63 tons 13 
 cwt. of nitre, or 3 '8 per cent.; chamber-space being 1 
 sulphur per twenty-four hours to 20 cubic feet, and all 
 the acid made being by the same process concentrated to 
 140 to 150 T. 
 
 Another advantage attached to the use of the Glover 
 tower is that all the water formed as steam in the deni- 
 tration by the sulphurous anhydride goes to the chamber, 
 and so an economy in the steam generated direct by fuel 
 is effected. Another alleged danger of the use of Glover 
 towers is the contamination of the acid by iron carried 
 up in the current of sulphurous anhydride from the 
 burner. But E. Hasenclever finds that in his hands, by 
 the Glover system, the acid contains only 0*05 per cent, 
 of iron. 
 
 It has been also said that a serious source of loss is 
 encountered under certain circumstances in working with 
 
RESUME OF THE SULPHURIC ACID MANUFACTURE. 43 
 
 these towers, viz., in the reduction of the higher oxides of 
 nitrogen to monoxide, or even to nitrogen itself, although 
 it has been also allowed that such a reduction takes place 
 when Glover towers are not used, if the proportion of free 
 oxygen entering the chamber be too low. 
 
 However, to conclude this review of pros and cons, it 
 may fairly be said that Mr. Glover process bears the 
 stamp of success, and is the most advanced process of the 
 day for denitrating nitrous sulphuric acid. 
 
 Through the kindness of Mr. William Glover we are 
 enabled to give an engraving of the tower (figs. 8 and 
 9), which is self-explaining. All we need add is, that the 
 towers are supplied with the nitrous sulphuric acid by 
 means of a Barker's mill in some works, which arrange- 
 ment equally distributes the acid over the area of tower. 
 
 In conclusion, what has been stated in detail may be 
 represented as follows : Taking the squares to indicate 
 the various pieces of plant in the order in which they are 
 arranged in the most modern way of manufacturing sul- 
 phuric acid, then we have 
 
 SULPJHUR 
 BURNERS 
 
 
 CLOVER'S 
 
 TOWERS 
 
 
 CHAMBERS 
 
 
 
 CAY-LUSSAC 
 TOWER 
 
 In the burners, sulphurous anhydride is generated, 
 and passing with air and nitric acid into the chambers, 
 meets with steam or atomised water and forms acid. From 
 the chamber-gas the oxides of nitrogen are abstracted by 
 strong sulphuric acid in the Gay-Lussac towers, and from 
 this product the oxides of nitrogen are taken and restored 
 to the chambers in the Glover towers, which also pre- 
 pare strong acid for the Gay-Lussac towers. 
 
 Concentration of Sulphuric Acid. The acid of 1*6 
 
44 
 
 THE ALKALI TRADE. 
 
 FIG. 8. 
 
 FIG, 9. 
 
CONCENTRATION OF SULPHURIC ACID. 45 
 
 sp. gr. (71 per cent. H 2 S0 4 ) from the chambers, is strong 
 enough for the manufacture of salt cake, but as it is not 
 strong enough for many other purposes it has to fulfil, its 
 concentration has to be effected. At first this concentra- 
 tion is allowed to proceed in leaden pans placed on plates 
 of cast iron, which are heated direct by fire and lined 
 with clay and fire-bricks until, in fact, its density is 1*720 
 (82 per cent. H 2 S0 4 ). At this stage it forms the * brown 
 vitriol ' of commerce, which is much used in the manufac- 
 ture of phosphatic manures. This degree of concentration 
 is often effected by the waste heat of the burners. The 
 pans are not filled deeper than 0'35 metre height (or 15 
 inches) of acid ; nevertheless, the wear on them is chiefly 
 on the bottom. This doubtless arises from the combined 
 action of fire and pressure exerted by the weight ot 
 the acid. When well managed, 1 cwt. of 60 B. acid 
 may be obtained from acid of 50 by 16 or 18 Ib. of 
 coal on the average (F. Bode). 
 
 Beyond a density of 1*720 the concentration cannot 
 be effected in leaden pans, not so much on account of 
 any action on the lead by the acid, but owing to an action 
 brought about by the acid, through the high temperature 
 at which it boils, two dangers thus appearing melting 
 of the lead, and its corrosion by the acid. Pure and soft 
 lead is more affected by acids than the harder varieties. 
 To further concentrate the acid, recourse was originally 
 had, as stated in the previous chapter, to distillation in 
 glass retorts. These, however, gave way to alembics of 
 platinum of capacity 10 to 30 gallons, and costing from 
 400/. to 800/. In these the concentration proceeded to 
 1-845 sp. gr. (100 per cent. H 2 S0 4 ). At this stage 
 sulphuric acid passes over, and, indeed, long before it 
 
46 THE ALKALI TRADE. 
 
 arrives at this state much acid is carried over with the 
 water, but means are taken to condense it and return it 
 to the chamber. 
 
 Platinum retorts, however, are costly, and are 
 much more readily attacked by acid than might be 
 imagined. This is especially the case with acid containing 
 an undue proportion of nitrous compounds. Kestner 
 found that when an alloy of platinum and iridium was 
 employed, this destruction was much less, but then such 
 an alloy is far less malleable than platinum alone, and 
 therefore far harder to work. 
 
 The cost of a retort in these days is about 4,000/. 
 for one capable of yielding half a ton of finished acid per 
 day. In Germany a platinum still costs from 30/. to 48/. 
 per kilo. But, although they are still used here and 
 there in England, and to a great extent on the Continent, 
 yet, practically, here at home they have been abandoned, 
 and have given way once more to improved glass retorts 
 (lead glass) heated by an open fire or in iron pots with 
 sand. Moreover, this method has the advantage of ren- 
 dering the progress of concentration evident by the loss 
 of brown colour. 
 
 In 1850, Mr. Clough, of America, patented the con- 
 centration of the acid, by surface heating in leaden pans, 
 which are placed in water and lined with fire-bricks, 
 and covered with a low arch of brickwork. Over 
 the surface of the acid, the flame of a reverberatory 
 furnace is passed. But this promising method is attended 
 with a considerable loss of acid, and after a time the 
 leaden pans are also attacked. 
 
 In the same year Mr. Gossage (junior) patented the 
 concentration of sulphuric acid by its distribution over 
 
THE CONCENTRATION OF SULPHURIC ACID. 47 
 
 pebbles contained in a leaden tower. From below, the 
 acid was met by a current of hot air, produced by the 
 combustion of coke ; but unfortunately here also, there 
 was a great loss of acid by evaporation in the vesicular 
 state. 
 
 It may be stated, that beyond concentrating the acid 
 to the strength at which it is employed for making sul- 
 phate of soda, these operations are carried on at distinct 
 works. 
 
 Some short time ago a method was discussed in the 
 columns of the ' Chemical News ' for concentrating sul- 
 phuric acid, which seemed somewhat promising. The 
 method originated with Mr. John Galletly and Mr. James 
 Stoddart, simultaneously and independently. 
 
 Mr. Stoddart points out, that by heating the acid to 
 300 Fahr. (a temperature maintained by fire) in a 
 current of air, the brown" acid of 1*700 sp. gr. can easily 
 be made, and at a temperature of 500 Fahr. (also in 
 a leaden pan), by these means, concentrated acid. Mr. 
 Galletly has repeatedly concentrated a gallon of brown 
 vitriol in a small leaden box, with a depth of acid of 
 4 to 5 inches, and a temperature varying from 190 C. 
 to 210 C. till its sp. gr. = 1*840. Paying especial 
 attention to the lead box, he concluded the action of the 
 acid to be very slight, of course through working at such 
 a comparatively low temperature. On another occasion 
 he prepared from brown vitriol (of 1'745 sp. gr.) 5 
 gallons of 1*830 sp. gr. at 205 ,C. in an hour, using 
 16J cubic feet of air. The loss of monohydrated acid 
 was 11*19 per cent, as against 8*8 per cent, by concen- 
 tration in glass bottles. At first the evaporated water was 
 practically free from acid ; the last fourth had a sp. gr. 
 
48 THE ALKALI TRADE. 
 
 of 1'OTO. He points out that enough heat, even from 
 the best-built pans, might be economised and utilised 
 to propel a small engine for blowing the requisite air. 
 
 Mr. F. Bode has commented on these proposals at 
 some length. He points out that, in employing the 
 above method, deeper pans than those usually employed 
 would have to be used, and this would necessitate a 
 thorough support at the bottom, owing to the in- 
 creased pressure of the hot acid- Further, it would be 
 necessary to cover the pans with a hood, to prevent 
 mechanical losses by spirting, and, even so, the formed 
 steam would carry over some acid in a vesicular 
 state not easily recoverable. At any rate, the method 
 is worth trying further, although, practically, it is the 
 same method as that of Mr. Gossage, above alluded to, 
 and open to the same objections. 
 
 Before leaving the subject 'we must allude to the 
 method which employs super-heated steam ; this ori- 
 ginated with Carlier, of Drusberg, and is now em- 
 ployed, according to E. Hasenclever, in many works 
 in Germany. The acid is placed in leaden-lined wooden 
 tanks of 4 metres square, and provided at the bottom 
 with two coils of leaden pipes, 45 metres long, 0*03 
 metre internal diameter, and 0*007 metre thickness of 
 lead. Through these coils high-pressure steam is forced, 
 until the sp. gr. of the acid is 1-7, when it is run into 
 another tank, through a serpentine leaden coil of pipes, so 
 that it reaches the second tank in a warm state, and there 
 the evaporation is continued. In an apparatus as here 
 mentioned, 5 tons of chamber acid are concentrated to 
 1*7 sp. gr. in twenty-four hours, with steam at a pressure 
 of 45 Ib. to the square inch a temperature 135*1, 
 
ACTION OF SULPHURIC ACID ON PLATINUM. 49 
 
 employing a quantity of fuel amounting to 9 per cent, of 
 the acid concentrated. The advantages of this method 
 are, first, the prevention of loss of acid by employing a 
 low temperature, and the non-contamination of the acid 
 by impurities. 
 
 According to MM. Favre and Kessler, there are 
 thirty- nine platinum alembics of a peculiar construction 
 at work in twenty-six works in France. They are com- 
 posed of wide, shallow, platinum cisterns, covered with a 
 leaden hood with double walls between which water 
 circulates to keep them cool. Connection between the 
 cistern and the leaden cap is effected by a hydraulic joint. 
 These cisterns are fed by means of a leaden pipe, with 
 acid of 60 B., and deliver full-strength acid through a 
 pipe of platinum. 
 
 Scheurer Kestner has recently determined the solubility 
 of platinum in sulphuric acid at various degrees of con- 
 centration. With acid free from nitrous compounds, 
 1 grm. of platinum is dissolved per 1000 kilogrammes of 
 acid concentrated to 94 per cent. When carried to 98 
 per cent. 6 or 7 grms. of platinum dissolve per 1,000 
 kilogrammes of acid concentrated, and 9 grms. when 
 carried to 99'5 per cent. H 2 S0 4 . In the presence of 
 nitrous compounds much more dissolves. 
 
 Statistics of the Sulphuric Acid Trade. A small 
 works will turn out about 150 to 200 tons of acid an- 
 nually, while a large one will often make more than 4,000 
 or 5,000 tons per annum. When it is to be sold or 
 exported, it is packed in carboys holding from 11 to 12 
 gallons, and containing about 200 Ib. each. 
 
 4 In 1830 the produce of acid on the Tyne may be 
 calculated at about 3,300 tons, and advancing to 1867, 
 
 E 
 
50 
 
 THE ALKALI TRADE. 
 
 and acting on more certain returns, it appears that the 
 production of sulphuric acid has increased to 140,000 
 tons ' (E. Calvert Clapham). Professors Schunck, Angus 
 Smith, and Eoscoe estimated that 700 tons of sulphuric 
 acid, of sp. gr. 1-85, were annually produced in the 
 Lancashire district, exclusive of that used for soda-ash 
 making. Besides its consumption in the soda trade, it 
 is largely consumed in the manufacture of soap, glass, 
 hydrochloric and nitric acids, alum, superphosphates 
 (manures), sulphate of copper, and in bleaching and 
 dyeing. A true estimate of the ' total make ' of sulphuric 
 acid can only be arrived at from a knowledge of the 
 amount of it used in these industries. Such tables we 
 shall give in a later chapter. 
 
 Strength of Sulphuric Acid of different Densities at 60 Fahr. or 
 15-5 Cent. (Ure) (Abridged). 
 
 Specific 
 gravity 
 
 Percentage 
 H 2 S0 4 
 
 Specific 
 gravity 
 
 Percentage 
 H 2 S0 4 
 
 Specific 
 gravity 
 
 Percentage 
 H 2 S0 4 
 
 1-8460 
 
 100 
 
 1-7901 
 
 88 
 
 1-6624 
 
 76 
 
 1-8415 
 
 98 
 
 1-7728 
 
 86 
 
 1-6415 
 
 74 
 
 1-8366 
 
 96 
 
 1-7540 
 
 84 
 
 1-6204 
 
 72 
 
 1-8288 
 
 94 
 
 1-7315 
 
 82 
 
 1-5975 
 
 70 
 
 1-8181 
 
 92 
 
 1-7080 
 
 80 
 
 1-5760 
 
 68 
 
 1-8070 
 
 90 
 
 1-6860 
 
 78 
 
 
 
 
 
 Purification of Commercial Sulphuric Acid. Com- 
 mercial sulphuric acid is always contaminated with 
 lead, and generally with arsenic, as we have already 
 shown. 
 
 A method, adopted in several Continental manu- 
 factories, for separating arsenic from oil of vitriol, con- 
 sists in heating the chamber acid with the necessary 
 amount of sodium hyposulphite at a temperature of 
 
PURIFICATION OF SULPHURIC ACID. 51 
 
 70 or 80, with some stirring. Sulphide of arsenic 
 separates out and collects in flakes on the surface, while 
 the acid containing an equivalent amount of sodium 
 sulphate is withdrawn from below. The arsenic can also 
 be removed by the use of sulphuretted hydrogen, or of 
 barium sulphide ; if the latter be used, sulphuretted 
 hydrogen is generated, and this forms sulphide of 
 arsenic, whilst the barium as sulphate remains undis- 
 solved. 
 
 3H 2 S + As 2 3 = 3H 2 + As 2 S 3 , 
 or 3BaS + As 2 O 3 + 3H 2 S0 4 = 3BaS0 4 + As 2 S 3 + 3H 2 O. 
 
 Lead can be removed from the acid by dilution with 
 water, when lead sulphate is precipitated; but when 
 this method is used, it is necessary to concentrate the acid 
 again afterwards. 
 
 Notes on the Sulphuric Acid Trade in the South of 
 France. According to M. A. Favre, the sulphuric acid 
 is entirely obtained from pyrites roasted in furnaces 
 capable of revolving on their axle. The depth of the 
 kiln being T80 m. and its surface 1*20 m. The pyrites 
 are burnt down to 2 or 3 per cent, sulphur, while the 
 combustion is incomplete in many works owing to the 
 use of too shallow layers of pyrites, so that the burning 
 is carried on too briskly. He approves of the following 
 proportions: 180 cubic metres of chamber space to 1 
 square metre of surface of kiln grating, upon which are 
 burnt every twenty- four hours 270 kilos, of pyrites at 
 40 per cent, sulphur, corresponding to 150 kilos, of 
 pyrites to 100 cubic metres of chamber-space. He con- 
 siders that the capacity of the chambers may be better 
 utilised by cooling the gases before they enter them. 
 The chambers are generally worked in sets of three, one 
 
 E 2 
 
52 THE ALKALI TKADE. 
 
 large and two smaller ones, and for the larger chamber 
 the most approved dimensions are 45 metres long, by 
 8 in width and 6 in height ; the three chambers giving 
 a total cubic bulk of 4,000 cubic metres. The cost of 
 1,000 kilos, of acid at 50 B. is stated at 36'9 fr. 
 
 Other Processes Proposed for Making Sulphuric 
 Acid. One cannot insist too strongly on the importance 
 of keeping up a knowledge of old processes and sugges- 
 tions, for, after all, our new processes are, in a limited 
 sense, old processes improved. Industrial processes, like 
 scientific laws, are generally the accumulation of indi- 
 vidual experiences rather than the work of one man. 
 One notes a fact, another extends the observations, a third 
 generalises, a fourth discerns a principle, and a fifth be- 
 yond recognising, establishes it. We shall therefore offer 
 no apology for once more placing on record the following 
 old processes : 
 
 (1) Shanks proposed to decompose gypsum with chlo- 
 ride of lead CaS0 4 + PbCl 2 = PbS0 4 + CaCl 2 , and then to 
 decompose the PbS0 4 with hydrochloric acid : PbS0 4 
 4-2HCl=PbCl 2 + H 2 S0 4 . The acid is removed and con- 
 centrated ; the PbCl 2 is used over and over again ; the 
 CaCl 2 is wasted. 
 
 (2) McDougall and Eawson patented the passage of 
 sulphurous acid through nitric acid. Sulphuric acid and 
 nitric oxide are formed, the latter being converted into 
 peroxide by air, and this is again decomposed by water 
 into nitric acid and N0 2 . The difficulty of the process is 
 presented in the management of the apparatus. There is 
 also a great wear and tear on the plant. 
 
 (3) Keller obtained sulphuric acid from lead sulphate 
 as follows. He obtained hydro-sulphuric acid, amongst 
 
OTHER PROCESSES FOR MAKING SULPHURIC ACID. 53 
 
 other methods, by exposing sulphate of calcium or barium 
 with coal and sand to steam in a heated state. The 
 hydrothion was conveyed into vessels holding in sus- 
 pension (in water) PbS0 4 . Sulphide of lead was precipi- 
 tated and yielded more PbS0 4 by roasting, while sulphuric 
 acid passed into solution. 
 
 (4) Margueritte decomposed clay with chloride of 
 magnesium, giving hydrochloric acid, which was used to 
 decompose phosphate of lime. He then decomposed 
 sulphate of lime by phosphoric acid, reproducing phos- 
 phate of lime and giving sulphuric acid. 
 
 (5) Schmersahl and Bouct passed a mixture of sul- 
 phurous acid, air, and steam through horizontal pipes of 
 clay or iron, filled with asbestos, pumice, or other porous 
 material, and heated in a furnace. But even before this, 
 as already pointed out, Wohler had discussed the facility 
 which CuO, Fe 2 3 , Cr 2 3 , at a low red heat, have for giv- 
 ing sulphuric acid in this way ; but at Oker the attempts 
 which were made to carry out these reactions on a large 
 scale, did not prove satisfactory. 
 
 (5) Dobereiner was the first to suggest the use of 
 spongy platinum for making sulphuric acid without cham- 
 bers. 
 
 (6) Under the heading 'Alkali Waste' other pro- 
 cesses, including Gossage's and Duclos', will be given. 
 
51 THE ALKALI TRADE. 
 
 CHAPTEE IV. 
 
 THE TREATMENT OF BURNT PYRITES ; EXTRACTION OF COPPER, 
 SILVER, AND GOLD ; AND THE MANUFACTURE OF SULPHATE 
 OF COPPER. 
 
 IN the present chapter we shall discuss the various 
 methods adopted for extracting from the burnt residuum 
 from the pyrites kilns, the several metals contained 
 therein, and the utilisation of the unburnt sulphur. These 
 several operations are often conducted in special works, 
 but the industry is so essentially a part of the alkali trade 
 as to warrant its complete study here. 
 
 In times gone by, the employment of cupriferous 
 ores for acid making was avoided as far as possible, but 
 now that processes have been devised for extracting the 
 copper, these ores have come largely into use, and are 
 quickly supplanting the other forms of pyrites. H. L. 
 Pattinson and Co, began to smelt copper ores obtained 
 from burnt pyrites in 1858, but for the most part, in 
 those early days of the trade, they had to be sent to 
 Swansea to undergo this extraction. But since copper 
 works were erected at Hebburn in 1865 to carry out this 
 extraction by the so-called ' wet method ' of Mr. Hender- 
 son, this example has been followed, and thus the ex- 
 pense of sending the ores to Swansea has been rendered 
 unnecessary. This process, so successfully worked out 
 by Mr. Henderson, we shall now describe, but, before 
 
HENDERSON'S COPPER EXTRACTION PROCESS. 55 
 
 doing so, we give the following analyses made by Mr. 
 Thomas Gibb, showing the amounts of copper and silver 
 contained in the burnt residuum of the chief varieties of 
 pyrites : 
 
 Kind of ore 
 
 Copper, per cent. 
 
 Silver 
 
 Rio Tinto 
 Tharsis .... 
 San Domingo's (Mason's) . 
 
 3-80 
 3-50 
 3-70 
 
 1 oz. 4 dwts. per ton. 
 15 ,, 
 15 
 
 Mr. Henderson's process begins by fluxing the burnt 
 pyrites with common salt, employing both in the state of 
 powder, at a low red heat. The sulphur present forms 
 sulphate of iron, which decomposes some of the salt, pro- 
 ducing therefore sulphate of sodium and chloride of 
 copper. Any chloride of copper that may sublime and 
 pass away with the hydrochloric acid which is generated, 
 is condensed with the latter in Gossage's towers, and the 
 liquors so obtained can be afterwards used entirely or 
 partly to lixiviate the furnace product. This lixiviation 
 is effected by water and the acid described, in wooden 
 tanks ; the acid assisting most effectually in dissolving 
 out the metals. In this way liquors are obtained con- 
 sisting of chlorides of copper, silver, and lead, with un- 
 decomposed salt and sulphates of sodium and lead. These 
 liquors are now precipitated in tanks by scrap iron, or 
 what is better, because of its more rapid action, spongy 
 iron, which latter is made by heating burnt pyrites with 
 coal in a muffle furnace. 
 
 The copper so obtained is washed, drained, and par- 
 tially dried, after which it is smelted in a reverberatory 
 
56 THE ALKALI TRADE. 
 
 furnace, yielding what is termed ' pimple ' copper (60 per 
 cent.), and this when melted in a current of air in a 
 similar furnace, is purified by the oxidation of impurities 
 which proceeds, and gives blister copper (86 per cent.), 
 which is lastly refined into ' finished ' or ' ingot ' copper, 
 ready for the market, and containing 96*5 per cent. Cu. 
 Mr. E. Calvert Clapham gives, as the rough analysis of 
 the tank residue remaining after the precipitation of the 
 copper, the following : Peroxide of iron, 90 tons ; silica, 
 6 tons ; water, 4 tons : total, 100 tons. This is largely 
 used for 'fettling' in puddling furnaces, and in blast- 
 furnaces, where it takes the place of hsematite. Mr. 
 Henderson's process for extracting the copper, it may be 
 remarked, likewise applies to weak copper ores. The 
 copper is dissolved out of the sandstone by hydrochloric 
 acid, and from the liquors the copper is precipitated by 
 iron. 
 
 It has been seen that the ores used in the sulphuric 
 acid manufacture often contain a considerable quantity of 
 arsenic, and a good deal of this remains in the burnt resi- 
 duum (about 0*5 per cent.), and ultimately in the above 
 process is precipitated more or less with the copper. 
 Now the presence even of traces of arsenic in copper, 
 renders it extremely brittle, and such copper finds any- 
 thing but a ready sale in the market. It is, therefore, a 
 matter of importance to rid the copper of this impurity. 
 This is done successfully at the Tharsis Works by a pro- 
 cess patented by Mr. Down in 1870. This process is 
 said to consist in treating the acid copper liquors, ob- 
 tained as described above, with such an amount of lime 
 or calcic carbonate as is sufficient to neutralise a great 
 deal of the excess of acid present. But, according to the 
 
REMOVAL OF AESENIC FROM COPPER LIQUORS. 57 
 
 specification, the copper liquors are by preference allowed 
 to remain in contact with the lime ' until the salts of iron 
 present in the solution with the copper begin to precipi- 
 tate.' The solutions are then run off into the tanks, 
 where the precipitation of the copper by metallic iron 
 takes place. Now Mr. Down claims that by this process, 
 while the excess of acid is neutralised, and thus an eco- 
 nomy in the amount of iron used for precipitation of the 
 copper, effected, there is yet sufficient acid left in the 
 solution to allow of that precipitation, and at the same 
 time to keep the arsenic and antimony in solution. He 
 further states that arsenic and antimony are precipitated 
 with the copper only when the liquors are very acid, so 
 that by working his process the copper is obtained free 
 from these metals. Now, while we do not for a moment 
 doubt the utility and practicability of the process, we are 
 inclined to interpret the changes effected in a way some- 
 what different to Mr. Down. That he gets the copper 
 free from arsenic we know, for we have on several occa- 
 sions examined such liquors after treatment by his pro- 
 cess, and found them free from arsenic. But where we 
 are inclined to differ from him is in the chemistry of the 
 process by which the arsenic has been removed. And 
 here we are writing from personal knowledge ; for, in 
 fact, soon after the date of Mr. Down's patent, we were 
 engaged in working with some processes devised for the 
 same purpose. 
 
 We have seen that Mr. Down preferably allows the 
 liquors to remain in contact with the lime until the salts 
 of iron begin to precipitate ; and although he expressly 
 says that in such case the greater amount of the arsenic 
 and antimony remain in solution, we are yet disposed to 
 
58 THE ALKALI TRADE. 
 
 think that the arsenic and antimony are actually removed 
 by the precipitate of ferrous oxide which occurs at this 
 stage, although it is of course small in amount. It has 
 been our universal experience, that whenever the acid 
 copper liquors, of which we are writing, are treated either 
 with lime in sufficient quantity to precipitate a small 
 quantity of ferrous oxide, or are treated with ferric oxide 
 itself, then all the arsenic present is removed by the pre- 
 cipitate, in combination, in a form similar to that in which 
 arsenic exists in ' Scheele's green ' ; the only difference 
 being that in ' Scheele's green ' copper exists in the place 
 of iron. Thus ' Scheele's green ' is CuHAs0 3 ; whereas 
 the iron compound may have a formula FeHAs0 3 , or more 
 probably, FeAs0 3 , "or the arsenic may be precipitated 
 in combination with the lime. If our view of the process 
 be correct, it would prove desirable to perform the pro- 
 cess in separate tanks to those in which the copper is 
 precipitated by the iron, otherwise the copper would still 
 be contaminated with the arsenic, although in a different 
 form. This is important, because, Mr. Down says, the 
 neutralisation may be effected wholly or in part in the 
 precipitating vats.' But, apart from the criticism we 
 have made, one thing is certain, that the process, when 
 carried out in a certain manner, gives excellent results 
 and yields copper free from arsenic. 
 
 The utilisation of the sulphate of sodium existing in 
 the mother liquors, after the precipitation of the copper, 
 has likewise been attempted by Dr. Merz and Mr. Napier, 
 and will, doubtless, shortly be a matter of consummation. 
 Mr. Calvert Clapham points out that this new copper- 
 extraction industry has had the effect of decreasing the 
 mining of native ores, with a corresponding increase in 
 
AUGUSTIN'S SILVER PROCESS. 59 
 
 the importations ; so that whereas in 1860 no less than 
 15,968 tons of native ore were raised, in 1869 only 8,291 
 tons were raised, equal to a reduction of nearly 50 per 
 cent. The copper made from ' burnt ore' in 1869, on the 
 Tyne, amounted to 4,100 tons, and in Lancashire and 
 other places to 3,500 tons : total 7,600 tons. This copper 
 trade has reduced the cost of sulphur to the soda maker 
 40 per cent, since 1865. 
 
 We will now proceed to consider processes which 
 have been devised and used for extracting from burnt 
 pyrites the small amounts of precious metals contained 
 therein. 
 
 We give here Augustin's process for extracting silver 
 from its ores, although it is not employed in the extrac- 
 tion from burnt ore of its silver. It is yet the basis of 
 several suggestions, and is of interest. The ores are 
 roasted with salt and the mass lixiviated with a solution 
 of salt, to dissolve out the chloride of silver. By dilution, 
 silver chloride would be precipitated, but it is found pre- 
 ferable to precipitate the silver by copper, with formation 
 of cupric chloride; the presence of which does not interfere 
 with its use for extracting fresh quantities of chloride of 
 silver. An improvement on this process was made by 
 Ziervogel, who avoids argentic chloride altogether, and 
 merely roasts the sulphurous ore in such a manner that the 
 sulphates of iron and copper are completely decomposed, 
 whilst the argentic sulphate remains undecomposed, as it 
 withstands a much higher temperature. 
 
 To effect this, the roasting is continued until sulphurous 
 acid is no longer evolved and the mass yields no sensible 
 amount of sulphate of copper to water. The argentic 
 sulphate is extracted by boiling water, and the silver is 
 
60 THE ALKALI TRADE. 
 
 precipitated by metallic copper as before. A small quan- 
 tity of silver is still retained in the undissolved residue of 
 oxides of iron and copper, and this may advantageously 
 be utilised by Augustin's process. Both these processes 
 are largely practised. 
 
 Percy has suggested the use of sodic hyposulphite as 
 a solvent for chloride of silver. The roasted products (of 
 ores and salt) are washed with hot, and then with cold 
 water, and afterwards digested in dilute hyposulphite 
 solution, and the silver precipitated from this as sulphide 
 by means of sulphide of sodium, sodic hyposulphite being 
 reproduced. 
 
 Now, although it had long been known that the cop- 
 per precipitate, extracted as above described by Hender- 
 son's process, contained notable quantities of the precious 
 metals, attempts to extract them on a profitable scale were 
 not undertaken until 1870. 
 
 Henderson and Down proposed to calcine the precipi- 
 tated metals, hoping to get the chloride of silver which 
 volatilises, condensed in a suitable apparatus, but no 
 precipitate was condensed when experiments were made 
 at Alderley Edge Mine, in Cheshire. The process now to 
 be described, and known as Claudet's process, is based on 
 the precipitation of the precious metals as iodide, and is 
 carried out previous to the precipitation of the copper. It 
 was introduced in the beginning of 1870, and is very 
 successfully worked at the Widnes Metal Works, by Mr. 
 J. Arthur Phillips. 
 
 The burnt ores, which have been roasted with salt, are 
 lixiviated in vats, and receive eight or nine washings, 
 with water alone or water acidified with hydrochloric 
 acid. The first three only contain a sufficient amount of 
 
CLAUDET'S SILVER PROCESS. 61 
 
 silver to be worth working. For removing the soluble 
 salts, hot water is employed ; and, as a large amount of 
 the salt used remains undecomposed, it acts as a solvent 
 for the chloride of silver produced in the furnace. 
 
 The first three washings, containing 95 per cent, of 
 the total silver dissolved, are alone treated. They are 
 first run into wooden cisterns of capacity equal to 2,700 
 gallons, where they settle. The yield of silver per gallon 
 is now ascertained by taking a measured quantity, to 
 which are added hydrochloric acid, potassic iodide, and a 
 solution of lead acetate. The precipitate so formed is 
 thrown on a filter, and, after drying, is fused with a flux 
 consisting of sodic carbonate, borax, and lampblack. The 
 resulting argentiferous lead is passed to the cupel, and 
 from the weight of the button of silver obtained the 
 amount of that metal in a gallon of the liquor is esti- 
 mated. In another vat the amount of soluble iodide cal- 
 culated from the test, is run into the settled liquor from a 
 graduated tank, and water added equal to one-tenth of the 
 volume of copper liquor ; the whole is now stirred and a 
 little lime-water added, after which it is allowed to settle 
 for forty-eight hours. This done, the supernatant liquors 
 are assayed, run off, and the tank again filled, the preci- 
 pitate which collects being washed into another vessel 
 about once a fortnight. It consists of plumbic sulphate, 
 argentic iodide and copper salts. The copper salts are 
 removed by dilute hydrochloric acid and worked up by 
 Henderson's process. To the mother liquor zinc is now 
 added, giving its iodide for use over again, and a precipi- 
 tate rich in silver and some gold. M. Claudet gives the 
 composition of this precipitate as follows : 
 
62 THE ALKALI TRADE. 
 
 Per cent. 
 
 Silver ' . 5'95 
 
 Gold 0-06 
 
 Lead 62-28 
 
 Copper 0-60 
 
 Zinc oxide 15*46 
 
 Ferric oxide . . . . .1-50 
 
 Lime 1-10 
 
 Sulphuric acid . . . . 7 '68 
 
 Insoluble residue . . . . 1*75 
 
 Oxygen and loss . . . . 3 '62 
 
 Total 100-00 
 
 The first six months' experience at Widnes showed 
 that ^ oz. of silver and 1/5 gr. of gold were extracted at 
 a total cost, including labour, loss of iodide, etc. from 
 each ton of ore worked, of Sd. per ton, or Is. 4cZ. per oz. 
 of silver produced. Deducting from this, 6d. the value 
 of 3 gr. of gold in each ounce of silver, the cost of the 
 production becomes Wd. per oz. of silver, and the expense 
 of working a ton of ore 5d. (Eeport of British Association, 
 1870). 
 
 Although Mr. Phillips has been so successful, other 
 extractors have been less so, and in some works, after a 
 trial, the process has been abandoned. One cause of the 
 want of success is, according to Mr. Thomas Gibb, F.C.S., 
 the presence of cuprous chloride in the liquors, and this 
 results when the ores, badly burnt or otherwise refractory, 
 are calcined in hand-worked furnaces, or when a high 
 temperature is employed in calcination. The following 
 tests of ores by Mr. Gibb show the great difference in the 
 relative proportions of cupric and cuprous chlorides in 
 calcined ores : 
 
 Cupric chloride (CuCl 2 ) 6-70 per cent. 4-03 per cent. 4-25 per cent. 3-75 per cent. 
 Cuprous chloride (Cu 2 Cl 2 ) Nil. 0-21 0-45 0-62 
 
OTHER PROCESSES FOR EXTRACTING SIL\ 7 ER. 63 
 
 When present in large quantity cuprous chloride is 
 precipitated on dilution of the liquors with water, and thus 
 the quantity of precipitate to be worked up is increased, 
 and in such a case, moreover, the silver is incompletely 
 precipitated by the iodide. That the process may be 
 worked with profit is sustained by the following facts com- 
 municated by a friend to the author. At the Euncorn 
 Soap and Alkali Works at Euncorn, the value of the silver 
 extracted daily was 4/., using 100 tons of burnt ore per 
 week. At an extra expense of 6d. per day for wages, and 
 with a total consumption of 12 Ibs. of potassic iodide, there 
 was extracted, during 50 days, silver to the value of 200/. 
 In his paper, Mr. Gibb has described a process which is em- 
 ployed in the stead of Claudet's by the St. Bede's Metal and 
 Chemical Company of Newcastle. Sulphuretted hydrogen, 
 obtained from alkali waste by means of hydrochloric acid, 
 is diluted with air, and passed by a blowing engine through 
 the copper liquors. But before blowing the copper in 
 the liquors is estimated by potassic cyanide. The blow- 
 ing, which lasts about twenty minutes, is continued until 
 a sample gives 6 per cent, less copper than the first test. 
 The precipitate is now allowed to settle, and is drained, 
 and the copper liquors drawn off to the precipitating 
 tanks. The precipitate is washed somewhat, and col- 
 lected in an expanded Needham and Kite Filter (a filter 
 which employs strong flannel bags with lateral pressure). 
 
 The following are average testings of liquors and 
 precipitate : 
 
 Solution tested 
 
 Copper per litre. 
 
 Silver, per ton of Cu. 
 
 Original solution 
 Desilvered solution . 
 
 Precipitated by H 2 S . 
 
 20-1 grms. 
 18-8 grms. 
 
 18 oz. dwt. 
 2 oz. 19 dwt. 
 
 1*3 grm. 
 
 15 oz. 1 dwt. 
 
64 THE ALKALI TRADE. 
 
 These sulphides are not quite free from chlorides, and in 
 the next operation, viz., calcination at a low temperature, 
 copper and silver chlorides are produced with oxide and 
 sulphate of copper. The calcined body is powdered and 
 lixiviated, first with water, which dissolves the sulphate 
 of copper and only a trace of silver, and subsequently 
 with hot solution of salt to dissolve the argentic chloride. 
 This last product always contains copper and some sul- 
 phate of lead. It is now mixed with lime-milk and the 
 resulting precipitate well washed to free from chloride of 
 calcium, after which it is digested in dilute sulphuric acid 
 to separate oxide of copper and again washed. After 
 drying it has a composition as follows : 
 
 Per cent. 
 
 Silver 877 
 
 Oxide of lead . . . . . 28-66 
 
 Oxide of copper . .. . . 3 '75 
 
 Peroxide of iron . . . . 2 '61 
 
 Lime 13-67 
 
 Sulphuric acid . . , .31-72 
 
 Chlorine 4'70 
 
 Water 4-20 
 
 Insoluble residue . . . 1'40 
 
 Total .... 99-48 
 
 Although this treatment is somewhat complicated, Mr. 
 Gibb says it has been adopted as the cheapest, after 
 several modifications have been attempted. 
 
 The proportion of silver recoverable from burnt ore, 
 viz., about 1 part per 60,000, yet amounts in Tharsis and 
 Mason's ores in value to 25. Qd. per ton, whilst the cost 
 of extraction by Claudet's or this process, is about IQd. 
 per ton of ore worked, and when it is considered that 
 350,000 tons are produced annually, the aggregate value 
 is not unimportant. 
 
IMPROVEMENTS IN HENDERSON'S PROCESS. G5 
 
 An important improvement has recently been intro- 
 duced into the working of Mr. William Henderson's 
 process, and the experience afforded at that gentleman's 
 works at Irvine is of the most satisfactory nature. The 
 improvements themselves were patented by Messrs. Chad- 
 wick and Jar dine, but they have become the property 
 of Mr. Henderson. The cuprous solutions obtained in 
 the Henderson process, and registering from 40 to 60 
 T., are diluted with water to about 20 or 25 T. To 
 the resulting solution is added a very weak solution of any 
 soluble lead salt, but in practice the acetate is preferred. 
 The quantity of lead acetate employed, is calculated as an 
 equivalent upon the silver present in the solution, and a 
 further quantity is used, equivalent to any salts of arsenic, 
 antimony, or bismuth that may be present. As tlu 
 original pyrites contain lead, in certain cases less acetate 
 may be employed than in others. Ordinarily about half 
 a pound of brown acetate is used per ton of ore, and in 
 this way there is produced on stirring, a cream coloured 
 precipitate, containing 53 per cent, of lead (as sulphate), 
 5 to 6 per cent, of silver, and 3 oz. of gold per ton of 
 precipitate. 
 
 From this precipitate, after proper washing, the gold 
 and silver may be obtained by smelting and refining in the 
 ordinary manner. Besides the simplicity of this process 
 in thus isolating the precious metals, it has the further 
 advantage, it is stated, of purifying the copper liquors by 
 causing the precipitation of arsenic and antimonic acids, 
 and any traces of bismuth that may be present, so that 
 the solution in its further treatment yields a very pure 
 copper. 
 
 Dr. Hoffmann has devised a process for utilising burnt 
 
 F 
 
66 THE ALKALI TRADE. 
 
 ores, which is said to be successful in its object. The 
 burnt residue, by systematic washing with water at 40 
 C., gives liquors which are treated with salt in the pro- 
 portion of one equivalent for each equivalent of sulphuric 
 acid present. The resulting sulphate of sodium on cool- 
 ing crystallises out, while the mother liquors contain zinc 
 chloride, salt, sulphates of iron and of zinc, and a further 
 amount of sulphate of sodium. When concentrated to 
 54 B. the salts are deposited, with the exception of zinc 
 chloride which may then be isolated. In this state it has 
 industrial applications, and is sold in Prussia at 18 J frs. 
 per 100 kilos., being used chiefly as a preservative for 
 railway sleepers. 
 
 Or by treatment with lime, zinc oxide may be 
 obtained, and from this the metal. The residue from the 
 first operation, consisting chiefly of iron oxides, is dried 
 in the air, during which it disintegrates, and Dr. Hoff- 
 mann finds that the pulverulent portion thus obtained is 
 almost completely free from sulphur, so that when sifted 
 from the larger fragments which contain sulphur, it may 
 be used as an iron ore. 
 
 Of course the process described above, for utilising the 
 zinc contained in pyrites, only applies to ores of a certain 
 character. The sulphuric acid works in Germany are 
 mainly supplied with ores derived from the mines near 
 Meggen ; these often contain as much as 6 per cent, of 
 zinc, which, becoming sulphate in the roasting process, 
 causes a loss of sulphur. 
 
 Before concluding this chapter, we must take some 
 notice of the manufacture of sulphate of copper, which is 
 also made, to some extent, from the copper obtained as 
 described from the burnt pyrites. Some years ago this 
 
MANUFACTURE OF SULPHATE OF COPPER. 67 
 
 branch of manufacture was conducted chiefly at Newcastle 
 or in its vicinity ; now it is no longer pursued there, but 
 is carried on principally at Macclesfield, also at Bolton- 
 le-Moors. 
 
 The copper derived from the burnt pyrites by the wet 
 method is calcined in an ordinary reverberatory furnace, 
 by which operation it is converted into cupric oxide. 
 The product is then dissolved in sulphuric acid, in cisterns 
 lined with lead, and after time has been allowed for the 
 liquors to settle, they are run into other tanks also lined 
 with lead, into which strips of lead project from bars 
 of wood laid across the vessels. To these strips and to 
 the sides of the pans the crystals of cupric sulphate which 
 form, attach themselves. 
 
 Considerable quantities of the product are exported to 
 Chili and Peru, where it is used in some processes for the 
 extraction of iodine. 
 
68 THE ALKALI TRADE. 
 
 CHAPTEE V. 
 
 HISTORICAL SKETCH OF ALKALI MANUFACTURE. 
 
 THE manufacture which will be next described is that of 
 ' salt-cake,' or sulphate of sodium, and as the production 
 of this is the first stage in the manufacture of alkali, it is 
 thought best to preface it with a historical sketch of the 
 alkalies, their uses, etc. 
 
 The word Lixivium , used by the ancient Bomans, is 
 evidently derived from Lix, signifying a lye made with 
 ashes. Lixa, another Latin term, signifies a worker in 
 ashes, and this in itself is a proof of the antiquity of the 
 art. Marcus Terentius Varro, the Eoman general, writ- 
 ing in the first century, tells us that the inhabitants upon 
 the Ehine, wanting sea-salt, used a substitute procured 
 from wood. In the excavations of the city of Pompeii, a 
 complete soap-boiler's shop was discovered, with soap in 
 it, which had evidently been made from oil and alkali, 
 and the soap, though 1,700 years had elapsed, was still 
 perfect. Several ancient writers describe nitrum, and in 
 the ninth century Geber the Arabian describes soda 
 distinctly, and actually distinguishes it from potash. 
 Pliny relates that the Germans of his day used potash for 
 soap-making. The word ' alkali ' is of Arabian origin, 
 being derived from kali (a species of vegetable) ; the 
 particle al, according to Albertus Magnus, having been 
 
OCCURRENCE OF SODA IN NATURE. 69 
 
 added to signify the importance of the substance over 
 that of the plant from which it is derived. 1 
 
 Mr. Eodwell, in his ' Birth of Chemistry/ tells us that 
 nitrum was a term applied to sodic carbonate by the 
 ancients, who used it for glass-making. In fact, glass is 
 supposed by Pliny to have been ' first discovered by 
 some Phoenician merchants who were returning from 
 Egypt with a cargo of natron (carbonate of soda), and 
 who landed on the sandy banks of the river Belus. In 
 order to support the vessels they used for cooking their 
 food over the fire, they used some large lumps of natron, 
 and the fire was sufficiently strong to fuse it with the fine 
 sand of the river. Hence resulted the first glass.' 2 Mr. 
 Eodwell shows that, whatever may be the worth of the 
 story detailed by Pliny, the ancients were proficient in 
 glass- making, and that the composition of the Egyptian 
 glass was nearly identical with that of our crown glass, 
 in the manufacture of which alkali is necessarily con- 
 sumed. 
 
 Soda in various forms occurs in nature very widely 
 and abundantly. As sesquicarbonate, 2ISra 2 0,3C0 2 + 3Aq, 
 it forms the deposits known as ' Trona ' and ' Urao,' left 
 by the drying up of soda lakes. As a mineral, in 
 combination with carbonate of calcium, it constitutes 
 Gay-Lussite, N^COg + CaCOg + SHjO. Its occurrence as 
 chloride (salt) will be further alluded to presently. But 
 it was from marine plants that our early supply was 
 derived ; such plants as salsola, triglochia, salicornia, 
 atriplex, all yield sodium carbonate on incineration. Sea 
 plants, as a rule, however, compared with land plants, 
 contain less soda and more potash. Sea weeds contain 
 
 1 Parkes' ' Chemical Essays.' 2 ' Birth of Chemistry/ p. 48. 
 
70 THE ALKALI TRADE. 
 
 or yield from 9 to 25 per cent, of ash calculated on the 
 weed dry at 100 0., and in this ash the potash ranges 
 from 4 to 24 per cent, and the soda from 2 to 24 per 
 cent. The following information, as likewise some which 
 has gone before, is taken from Eichardson and Watts' 
 ' Technology :' 
 
 100 parts ash from salsola clavifolia 
 salsola soda 
 
 halmiocucnmm caps cum 
 
 solsola kali 
 
 kochia sedoides 
 
 salsola brachiata 
 
 gave 45-99 per cent. Na 2 C0 3 
 40-95 
 36-75 
 34-00 
 30-84 
 , 26-26 
 
 Previous to the year 1793, soda was obtained exclusively 
 from the ashes of marine plants, the chief quantities being 
 derived from Alicante in Spain, Sicily, Teneriffe, and the 
 coasts of Great Britain. Eussian and American potashes 
 were also largely imported. In fact, so large had grown 
 this importation, that during our dispute with America a 
 considerable quantity of saltpetre was consumed in Great 
 Britain to furnish alkali, by heating it with charcoal or 
 other carbonaceous matter. 1 The pearlashes were pre- 
 pared from potashes by calcination, whereby sulphur and 
 carbon were burnt away, the product being employed for 
 the nicer purposes. These potashes were prepared from 
 the -ashes of burnt wood. In the middle of the last 
 century the Eussian product was far superior to the 
 American. 
 
 The plants described above, furnished the soda of 
 Alicante and Carthagena, or (as it was commonly known) 
 ' Barilla,' and were sown as seeds in the end of the year 
 and gathered in the following September. So highly was 
 the product valued, and the importance of the trade 
 
 1 Parkes' ( Chemical Essays.' 
 
BARILLA AND KELP. 71 
 
 regarded, that by the laws of Spain the exportation of 
 the seed was an offence punishable by death. The plants 
 were mowed down, sun-dried, and burnt on iron bars 
 placed over pits 3 feet deep by 4 feet square. The ashes 
 fell into the pit, on the floor of which they formed a senri- 
 vitrilied mass, which was allowed to cool, then broken 
 into pieces, and in this state it formed the commercial 
 barilla, the best qualities of which contained about 40 per 
 cent, carbonate of soda. 
 
 ' Kelp ' was another commercial form of soda, and 
 its manufacture on our shores (Wales and Scotland) was 
 introduced from Ireland, by MacLeod in 1730, to the 
 Highlands of Scotland. It is said that Lord Macdonald 
 of the Isles realised 10,000^. a-year from his kelp shores 
 alone. British kelp was inferior to the Spanish barilla, 
 seeing it contained more potash, neutral salts, and car- 
 bonaceous matter. These rough alkalies were bruised 
 and mixed with quicklime and lixiviated, to furnish the 
 lyes used by soap-makers. They also furnished the 
 supply for the manufacture of glass. According to Bich- 
 ardson and Watt's ' Technology,' kelp is still produced for 
 making iodine and potash salts, while the mother liquors 
 are boiled down to dryness, and yield ' kelp salts ' con- 
 taining from 7 to 14 per cent, of alkali, which are sold 
 to the soda makers. In 1834 there were imported 
 12,000 tons of barilla ; in 1850 there were imported 
 34,880 cwt. of barilla; in 1856 there were imported 
 54,608 cwt. of barilla. Scotland alone produced at one 
 time 25,000 tons of kelp annually, so that we did 
 not depend on the Spanish product so much as other 
 countries. 
 
 The French Bevolution of 1793 stopped the importa- 
 tion of soda into France, whereupon the Convention made 
 
72 THE ALKALI TRADE. 
 
 an appeal to the nation, and appointed a committee to 
 discover the means of supply from native resources. Out 
 of thirteen processes which were reported upon, that of 
 Le Blanc was approved. Mr. Gossage has shown that 
 the process was not an outcome of this appeal, but that 
 Le Blanc had not only devised it previously, but had 
 also worked it on a considerable scale. We have alluded 
 elsewhere to the terrible privations which attended the 
 life of this great man, and the sad story of his death. 
 Sundry works were erected in France to carry out his 
 process, but it was not till some years later that it was 
 introduced into England. 
 
 At first, when introduced into England, the trade did 
 not develope as might have been expected, because of 
 the duties which then existed on salt, the substance from 
 which the soda was derived by this process. The aboli- 
 tion of these duties in 1823 was in no small measure 
 due to Mr. Parkes, and he ultimately received the con- 
 gratulations of the Commons for his efforts. So great an 
 effect had the abolition of the duties on the price of salt, 
 that it rapidly fell, even in London, from 35/. to 21. 10s. 
 per ton. When once fairly introduced into England, 
 the manufacture of soda assumed such a rapid develop- 
 ment that in a few years it formed the most important 
 chemical industry of the kingdom important, as Eichard- 
 son and Watts point oat, on account of the capital em- 
 ployed, the labour employed, and the uses of the manu- 
 factured products. 
 
 This process of Le Blanc has three stages: (1) The 
 decomposition of common salt by sulphuric acid ; (2) the 
 decomposition of the ' salt-cake ' so formed by chalk and 
 carbon; and (3) the separation of the carbonated alkali 
 
VAKIOUS SODA MAKING PROCESSES. 73 
 
 by lixiviation and its purification. These stages will be 
 separately described, together with those improvements 
 which have nearly all been introduced by Englishmen, 
 and which are mainly directed, not to supersede Le 
 Blanc's process, but to perfect it by the recovery and 
 utilisation of once waste products. But before passing 
 on to consider these processes, it may be of some interest 
 to look at earlier attempts which were made to manufac- 
 ture cheap soda. 
 
 Scheele, who discovered chlorine and its bleaching 
 effects, also discovered that chloride of sodium was de- 
 composed by oxide of lead, and previous to the introduc- 
 tion of Le Blanc's process, soda was manufactured in this 
 way at Walker, by Mr. Losh, the yellow lead compound 
 which was formed being sold as ' Turner's Patent Yellow/ 
 Le Blanc's process is practically an improvement on the 
 combined processes of Malherbe and Higgins. In 1778 
 Malherbe decomposed sulphate of sodium (it was well 
 known at that time how to prepare this body) by reduc- 
 tion with charcoal. Iron was then thrown in, then more 
 charcoal, then iron again, and so on, until sulphuretted 
 hydrogen ceased to be evolved. The mass on lixiviation 
 gave caustic soda. The proportions employed were : 
 Calcined sulphate of sodium, 100 parts ; charcoal powder, 
 20 ; red-hot charcoal, 11 ; iron scales, 33 parts. And in 
 this way the process was actually in work at Javelle, near 
 Paris, before the date of the Eevolution. 
 
 In 1781, Mr, Brian Higgins formed sulphate of sodium 
 from salt and sulphuric acid, and roasted the product 
 when dry, with one- eighth of its weight of coal in a 
 reverberatory furnace. Metallic oxides of the heavy 
 metals were then thrown in, and so caustic soda obtained. 
 
74 THE ALKALI TEADE. 
 
 It has been already mentioned that a certain quantity 
 of sodic carbonate was manufactured in this country 
 during our dispute with America, and how it was ob- 
 tained from soda-nitre and charcoal. In 1737, Duhamel 
 patented a process for making carbonate by reducing 
 sulphate of soda with charcoal to sulphide, and the 
 decomposition of the product with acetic acid. The 
 acetate so obtained yielded carbonate of soda on ignition. 
 These processes undoubtedly contained among them what 
 may be called the germs of Le Blanc's process, which 
 Mr. Losh learned on the Continent in 1802. On his 
 return to England he worked it at Walker, with per- 
 mission of the Government ; and in 1823 Mr. Mus- 
 pratt manufactured carbonate by this process in its 
 entirety. 
 
 In the present day the whole of the soda manufac- 
 tured is produced by the same process. It is interesting 
 to note that in 1814 soda crystals cost 60/. per ton, 
 while in 1861 the price had fallen to 4/. 10s. per ton. 
 
 In 1861 there were fifty soda works in Great Britain, 
 producing about 3,000 tons soda ash and 2,000 tons soda 
 crystals ; 250 tons of soda bicarbonate per week, besides 
 400 tons of bleaching powder. The total annual value 
 of the products exceeded two millions sterling, while 
 10,000 workmen were employed, exclusive of those 
 employed in mining operations and navigation. 
 
 The prices of materials at this date were as follow : 
 Salt, 8s. per ton ; sulphur from pyrites, 5/. ; limestone, 
 6s. 8d. ; fuel, 6s. per ton. 1 Mr. Cobden, by negotiating 
 
 1 ' History of the Alkali Trade/ by Gossage, and Richardson and Watts' 
 ' Technology.' 
 
EXTENSION OF THE SODA TRADE. 
 
 75 
 
 the commercial treaty with France, opened a new market 
 for our products. 
 
 The figures given above, contrast strikingly with the 
 price of soda not so many years previously. Kelp, con- 
 taining on an average 30 per cent, alkali, was at the close 
 of the last century III. per ton, a price which would render 
 a ton of soda-ash worth ISO/. The present price of soda 
 is about 8/. per ton. 
 
 The growth of the soda manufacture in this country 
 is well exhibited by the following figures, which we are 
 enabled to give through the kindness of Mr. Richard 
 Call and Mr. Edmund K. Muspratt (hon. secretaries of 
 the Soda Association). 
 
 SALT DECOMPOSED 
 
 EXPORTS OF ALKALI 
 
 Year 
 
 Lancashire 
 Branch 
 
 Tyne Branch 
 
 Total 
 
 Quantity 
 
 Value 
 
 
 Tons. 
 
 Tons. 
 
 Tons. 
 
 Cwt. 
 
 . 
 
 1860 
 
 
 
 
 
 250,000 
 
 2,049,582 
 
 965,348 
 
 1866 
 
 194,000 
 
 157,000 
 
 351,000 
 
 2,997,479 
 
 1,613,207 
 
 1869 
 
 164,922 
 
 141,983 
 
 306,905 
 
 3,514,382 
 
 1,379,108 
 
 1874 
 
 267,987 
 
 191,769 
 
 459,756 
 
 5,010,616 
 
 2,618,034 
 
 Statistics regarding the quantities of the principal 
 articles whose manufactures start with the decomposition 
 of salt, we reserve until such manufactures shall have 
 been studied. 
 
76 THE ALKALI TKADE. 
 
 CHAPTEK VI. 
 
 MANUFACTURE OF SALT, SULPHATE OF SODIUM, 
 AND HYDROCHLORIC ACID. 
 
 THE manufacture of sulphate of sodium employs, as at 
 present practised on the largest scale, sulphuric acid and 
 salt, and having already described the sulphuric acid manu- 
 facture, we propose, in the first place, to make a few 
 observations on salt. Salt must be regarded as one of the 
 chief materials consumed in the alkali trade, for it is from 
 the simple combination so familiar to us, that the soda 
 maker manufactures his soda and his chlorine, the first of 
 which is indispensable to the soap maker, and the second 
 indispensable to the bleacher. It has been a familiar sub- 
 stance from the earliest ages, and it is connected with 
 many proverbs and superstitions ; among the Eastern 
 nations it is an emblem of hospitality. To the human 
 economy it is likewise essential, for by it, as a food, the 
 stomach is enabled, by a process of decomposition and 
 recombination of its elements, to perform its functions of 
 digestion. It is most widely distributed in sea- water, 
 which contains about 2' 7 per cent., an amount equivalent to 
 4 oz. per gallon, or about a bushel in 300 to 350 gallons ; 
 and in earlier days it was from sea-water that the chief 
 supply was derived by a process of simple concentration, 
 when the salt crystallised out. Water dissolves 27 per 
 cent, by weight of salt, but if it contains 27*4 per cent. 
 
MANUFACTURE OF SALT. 77 
 
 of chloride of magnesium (a body present in sea-water) 
 it can only dissolve 2 per cent, of salt. From this fact, 
 we see the importance attached to the concentration of 
 sea-water, for the greater the concentration the more salt 
 is deposited. From Eichardson and Watts' 'Technology' 
 we learn that, even so far back as the reign of Edward 
 the Confessor salt was manufactured from the brine pits 
 that occur in the ' wiches ' of Cheshire, the beds not hav- 
 ing been discovered until the year 1670. Again, at We- 
 vertham, brine has been worked since the days of William 
 the Norman. One of the most remarkable brine springs 
 in the world is that of Montiers in Sardinia, where nearly 
 3,000,000 Ib. of salt are obtained annually from water 
 less strong in salt than sea- water. Halle furnishes 300,000 
 tons per annum by the same process. In Siberia the 
 climate is taken advantage of, by freezing the brine water 
 and removing the ice, which leaves a mother liquor strong 
 in salt. At one time, even on our own shores, salt was 
 extracted from sea-water, but this method has practically 
 passed away, although salt works exist still on the coast 
 of Spain, France (Mediterranean shore), Italy, Sardinia, 
 Sicily, etc. At these places, bay salt is obtained by spon- 
 taneous evaporation, when it is deposited until the density 
 of the liquors becomes 1'262, after which, mixed salts 
 (chloride of sodium, sulphates of magnesium, potassium, 
 etc.) are deposited. The mother liquors are a source of 
 bromine, and are known as ' bitterns,' and from them and 
 the mixed salts, sulphate of sodium and potassium salts 
 are made by Merle's modification of Balard's process. 
 Originally, carbonate of potash was also among the pro- 
 ducts made from mixed salts. 
 
 The mean produce of a salt-work is given by Eichard- 
 
78 THE ALKALI TRADE. 
 
 son and Watts as follows : 250 English acres, or 100 
 hectares of surface, produce 10,000 tons of sea-salt; '800 
 tons of salts (from liquors of 32 to 35 B.) giving 160 
 tons of Na 2 S0 4 ; and 600 tons of salts (from liquors of 
 35 to 37-5 B.) giving 40 tons of K 2 C0 3 . 
 
 Eock salt is another source, though the product often 
 requires recrystallisation before it is ready for the market. 
 The manufacture in Germany differs from the English 
 proceedings, but consists, nevertheless, in spontaneous and 
 artificial evaporation of brine liquors from springs, etc. At 
 Salzburg the process is known as the graduation process, 
 and is employed for liquors weak in salt. These are 
 pumped to a height, and allowed to trickle over stacks of 
 faggots freely exposed, but screened from the rain. A 
 great surface evaporation is thus effected, and after this 
 process has been repeated eight or nine times, when the 
 density of the liquors is about 1*140, they are concen- 
 trated by heat. In the first basin or pan the deposit con- 
 sists chiefly of insoluble double sulphate of sodium and 
 calcium, Na 2 Ca(S0 4 ) 2 , and is known as 'schlot.' At 1-236 
 sp. gr. the liquor is decanted into another pan and further 
 evaporated, when crusts of salt form and are removed 
 from time to time. 
 
 Table salt is obtained by rapid evaporation, and is fine- 
 grained, whereas ' fishery salt ' is hard and highly crystal- 
 lised, being obtained by slower evaporation. It may here 
 be remarked that the deliquescent character of common 
 salt is chiefly derived from the presence of chloride of 
 magnesium, which possesses this character in an eminent 
 degree. Most of the salt now consumed in England is 
 obtained from the vast beds which occur in Cheshire. 
 There are also large beds at Wieliczka in Poland, which 
 
STATISTICS OF THE SODA TRADE. 79 
 
 it is said contain enough salt to supply the world for ages, 
 the mine being 500 miles in length, 20 miles broad, and 
 1,200 feet thick ; it occurs in the Chalk formation. 
 Cardona in Spain, and Belfast, likewise have beds of salt. 
 The beds of Cheshire chiefly occur in the Magnesian Lime- 
 stone. At Northwich there are two beds, 30 feet apart, 
 being separated by clay and marl ; together they possess 
 a thickness of 60 feet, and are 300 yards broad and 
 1^ mile long. The salt is purified by re-solution and re- 
 crystallisation when necessary, and where coal is cheap, 
 water is often let down into the mine, and the liquor is 
 then pumped up and treated by evaporation, etc. Many 
 improvements have of late years been introduced into the 
 manufacture, most of them having reference to the economy 
 in fuel, and the preservation of the pans. The total pro- 
 duce in the United Kingdom for 1860 amounted to 
 1,570,972 tons. Germany in 1846 produced 339,703 
 tons. Besides its enormous consumption in the alkali 
 trade, it is extensively used in glazing stoneware goods, 
 and for preserving and salting purposes. 
 
 It is of some interest to note here the analysis of the 
 brine derived from the salt spring at Walker, from which 
 the first quantities of alkali made in England were pro- 
 duced. The analysis was made by a Mr. G. Woods, and is 
 stated by Mr. E. Calvert Clapham as follows : 
 
 CONTENTS IN 1,000 GRAINS OF BRINE. 
 
 Chloride of sodium . . . . 32 grains. 
 
 Chloride of calcium . . . . 10 
 
 Chloride of magnesium 
 
 Carbonate of lime 
 
 Carbonate of iron . 
 
 Silica ...... 
 
 Total .... 43 grains. 
 
80 THE ALKALI TRADE. 
 
 It was upon this brine that the experiments of Mr. 
 Losh and the Earl of Dundonald were first commenced, 
 and were continued until the repeal of the duties on salt. 
 
 An idea of the amount of salt consumed may be 
 formed from the following figures. 
 
 In 1869 there were decomposed in Great Britain no 
 less than 326,000 tons of common salt, 142,000 tons of 
 which were treated in the Newcastle district, and most of 
 the rest in Lancashire. It was estimated (according to infor- 
 mation kindly furnished by Mr. Eichard Cail) that in 
 1874, as much as 202,000 tons of salt were decomposed in 
 the Tyne district alone, while the amount decomposed in 
 the Lancashire district was considerably greater. These 
 figures will also furnish some idea of the growth of the 
 trade during the last few years. 
 
 We will now consider the process of decomposition 
 of salt by means of sulphuric acid. In early days this 
 was effected in ordinary reverberatory furnaces with brick 
 beds, the hydrochloric acid which formed (according to 
 the equation) being allowed to escape : 2NaCl-fH 2 S0 4 = 
 Na 2 S0 4 -f-2HCl. The first improvement of any note in 
 the construction of the furnace, was the introduction of 
 leaden linings or pans in the furnace ; but this gave way 
 shortly to a plan introduced by Lee and Gamble, who 
 employed iron pots, which were charged with from 4 to 
 8 cwt. of salt, and enough sulphuric acid of 130 T. at a 
 temperature of 120 Fahr. This sort of pot was com- 
 bined with two drying flats, whereon the decomposition 
 was completed, so that three charges were in operation at 
 one time. But even with these arrangements it will be 
 seen that no precautions were taken to preserve the hydro- 
 chloric acid gas from dilution with the air in the furnace. 
 
THE DECOMPOSITION OF SALT. 81 
 
 When therefore, it was desirable, and ultimately compul- 
 sory, to condense the hydrochloric acid, an operation 
 somewhat difficult to effect in such a diluted condition, 
 the iron pots were provided with semicircular covers, by 
 means of which the acid was kept free from contamination 
 with air and the products of combustion. Ultimately 
 also, the drying flats of the reverberatory furnace, gave 
 way to muffle furnaces, which were constructed with the 
 same objects in view. In such cases 16 cwt. of salt con- 
 stituted a charge with 1,800 Ib. or 123'5 gallons of sul- 
 phuric acid of sp. gr. 1*45 and at 120 Fahr. The mix- 
 ture was raked about, covered with the hood and fired, 
 when about one hour was sufficient to expel all the hydro- 
 chloric acicl. Eichardson and Watt, from whose work 
 these figures are taken, state that two such furnaces will 
 turn out about ten charges a day, being equivalent to 
 nearly 19 tons of ' salt-cake ' production from 16 tons of 
 salt. 100 parts of salt give 62 parts of dry hydrochloric 
 acid, and about 116 parts of salt-cake, against 121*5 parts 
 Na 2 S0 4 required by theory. As these furnaces are now 
 constructed, the cover to the pot has two doors, through 
 one of which the charge is introduced, whilst by means of 
 the other it is transferred to the 'roaster furnace/ These 
 ' pots ' are about 9 feet in diameter, and made of cast iron 
 2 to 7 inches thick, the cover being of a similar construc- 
 tion with a maximum depth of 1 foot. The fire is made 
 to pass over the cover and under the pot. The ' muffle ' 
 is adjacent to the pot, and constitutes a chamber of about 
 30 feet long by 9 feet wide, heated by fire from one end 
 which traverses a space left between the muffle and its 
 outer roof, and which extends also beneath and along the 
 bed of the furnace. Half a ton of salt is a convenient 
 
 G 
 
82 THE ALKALI TRADE. 
 
 and ordinary charge although the charge varies from 
 5 to 18 cwt. salt and in about one a half hour two- 
 thirds of the hydrochloric acid are expelled from the 'pot.' 
 On the bed of the muffle it loses the other third by decom- 
 position of the bisulphate with undecomposed salt. 
 
 NaHS0 4 + NaCl=Na 2 S0 4 + HC1. 
 
 The respective gases are kept separate, and are tech- 
 nically known as ' pot ' and ' roaster ' gas. 
 
 Within the last year another form of furnace for 
 producing salt-cake has been devised and patented by 
 Messrs. Cammack and Walker. In principle it resembles 
 an ordinary sausage-machine. The salt is charged into 
 a hopper at one extremity of the furnace, which is tubular 
 in construction, and thence into the furnace by means of 
 a continuous spiral screw which travels along the entire 
 length of the apparatus. The progress therefore of the 
 salt into the furnace is very gradual and uniform, while 
 the sulphuric acid is charged upon it by means of an 
 automatic arrangement which supplies it at the desired 
 speed, in a thin stream. Thus, all the hydrochloric acid 
 generated is of one strength, and readily condensible in 
 the towers ; meanwhile, as the mass travels through the 
 furnace it is gradually converted, so that it issues at the 
 other extremity as finished salt-cake. Expectations are 
 high in regard to this plant, but so far as experiments 
 have been conducted at the works of Messrs. Golding, 
 Davis, and Co., of Widnes, they have not been of a tho- 
 roughly decisive character so far as we can learn. We are 
 informed that the ' turn-out ' or capability of a cylinder 
 21 feet long amounts to about 50 tons of salt-cake at 95 
 per cent per week. There is a rumour to the effect that 
 
SALT-CAKE FURNACES. 
 
 83 
 
 a danger is anticipated from crusting of the material on 
 the cylinder sides. 
 
 It is impossible, however, to speak in any decided terms 
 in regard to this new furnace and its working results. 
 
 Among other new forms of furnaces recently patented, 
 there is one by Mr. James Mactear, which promises good 
 results. 
 
 The amount of ' salt-cake ' (sulphate of sodium) made 
 in a pot varies from 50 to 75 tons, while the total 
 amount a pot turns out varies from 1,000 to 2,000 tons. 
 Through the courtesy of Messrs. Daglish and Co. we are 
 enabled to give plan and elevations of decomposing pot 
 
 FIG. 10. 
 
 Scale inch to the foot. 
 
 and roaster as employed in many works. (Figures 10, 
 11, and 12). Of late years many manufacturers have 
 resorted to Siemens' gas method of heating these furnaces. 
 The gas furnished in the coal roasters is allowed to de- 
 posit its tar and ammoniacal liquor in metal or earthen- 
 ware condensers, which are constructed in the form of 
 large tubes or pipes of 2 to 3 feet in diameter. The 
 supply of gas mixed with the air necessary for its com- 
 bustion is regulated by a valve, and passes under the pot, 
 and then over the furnace. 
 
 In a plan patented by Deacon and Eobinson, the heat 
 
 G 2 
 
84 
 
 THE ALKALI TRADE. 
 
 for the pot was generated in an ordinary cupola supplied 
 with a blast and an ashpit, situated away from, but in 
 
 FIG. 11. 
 SECriON THRO 'JL.K 
 
 
 
 
 Scale \ inch to the foot. 
 
 proximity to, the furnace. As already stated, before the 
 bleaching industry assumed its present importance, and 
 
 FIG. 12. 
 
 SECTION THRO'C.K 
 
 Scale i inch to the foot. 
 
CONDENSATION OF HYDROCHLORIC ACID. 85 
 
 when therefore, the hydrochloric acid generated had 
 little or no value, it was allowed to escape, and desolated 
 the country around for miles, destroying vegetable life of 
 all kinds. 
 
 But when its employment as a source of chlorine to be 
 used in the manufacture of bleaching powder increased, 
 various means were proposed and used to condense and 
 utilise it. Where it proved a curse to the neighbourhood, 
 it was condensed by causing it to traverse long chambers 
 or towers packed with limestone moistened with water, 
 when chloride of calcium formed and was discharged, 
 being valueless. Kuhlmann passed it through a series of 
 stoneware vessels through which a stream of water ran 
 in an opposite direction to the gas current ; the water 
 towards the end of the series being mixed with witherite 
 or native barium carbonate, produced chloride of barium, 
 which was used for making permanent white (sulphate 
 of barium). In France the acid was absorbed by sets 
 of carboys containing water, with imperfect results. But 
 the time was drawing near, when, by Act of Parlia- 
 ment, perfect condensation was rendered compulsory, 
 whereby, indeed, new resources of wealth were opened 
 to manufacturers who were hitherto content to throw 
 away this now valuable product. Gossage had already 
 introduced a much more perfect system of condensation, 
 by means of towers packed with lumps of coke, over 
 which a stream of water was disseminated falling, and 
 into one of these towers the gas entered at the bottom and 
 rose to the top, while that which remained unabsorbed 
 passed into a second tower, where the condensation was 
 completed. The draught for causing the gases to pass 
 through these columns was supplied by the chimney of 
 
86 THE ALKALI TRADE. 
 
 the works, but Mr. Bell patented the use of a steam-jet 
 for aiding the draught, through its action as an aspirator. 
 Mr. Clapham, however, effected the object in a better 
 way, by pumping up the weak acid from the second 
 tower to absorb fresh gas in the first one. Sometimes 
 flint is used instead of coke. Mr. Gossage's plan has 
 developed and extended, and works so well that since 
 the Alkali Act of 1863, which renders the condensation 
 of 95 per cent, of the hydrochloric acid compulsory, 99 
 per cent, condensation has been common. These conden- 
 sers are generally constructed of Yorkshire flagstones, and 
 supplied with a cistern at the top, and a well at the base 
 for collecting th e acid which is of a strong yellow colour, 
 and averages 35 T. 
 
 The sulphate of sodium produced as described, aver- 
 ages from 96 to 97 per cent., and when good it readily 
 crumbles by pressure between the fingers. When care- 
 lessly made it is hard, lumpy, and yields inferior results 
 in its subsequent employments. But, perfect as the pro- 
 cess is, there is a considerable loss of sodium, which 
 amounts on the average from 2 2*5 per cent, as unde- 
 composed salt, and an additional -5 to I'O per cent, 
 mechanical loss. To refine salt-cake it is dissolved in water, 
 and treated with a slight addition of lime to precipitate 
 any iron that may be present, in the form of oxide. The 
 settled liquor is next evaporated to dryness, and the pro- 
 duct furnaced, and in this state it is ready for the market. 
 The hydrochloric acid gas is conducted from the furnaces 
 to the condensers by earthenware pipes covered with tar 
 and clay, to prevent cracking by the rain or other cooling 
 influences. In certain works, glass pipes are now used : 
 these have a diameter of about 15 inches, and are 
 
JONES'S AND WALSH'S FUKXACE. 87 
 
 loosely packed so as to allow of expansion by the hot 
 gases which they convey. They are so constructed that 
 they fit one into the other, and in this way the trouble of 
 having the pipes luted together is rendered unnecessary. 
 These glass pipes are protected by a w r ooden shade. 
 
 Notwithstanding the improvements that have been 
 effected in the construction of the ' decomposer,' much 
 expense and inconvenience are often caused by stop- 
 page of work through breakage of the pans, and hence 
 many attempts have been made to improve them. 
 Thus in 1860, Mr. E. Calvert Clapham had some pans 
 made of fire-clay, which were used at Walker, and found 
 to work very well, except that they were difficult to heat. 
 Eecently the same gentleman, in a paper read before the 
 Newcastle Chemical Society, has described a new form of 
 furnace, patented by Messrs. W. Jones and J. Walsh, by 
 the use of which the decomposition of salt is completed 
 in one furnace. Several such furnaces are already in 
 work ; they are constructed in the form of a metal dish, 
 composed of six segments or plates of metal 2^ inches 
 thick, resting on solid brickwork. ' The diameter is 15 
 feet, and the charge of salt is about 12 tons each twenty- 
 four hours ; so that a furnace of this capacity will turn 
 out about 80 tons of sulphate of soda in six days. The 
 batch is kept in constant motion by means of two cross 
 metal arms, worked from a centre shaft, to which are 
 fixed paddles and rakes, and the whole mass is much 
 more completely mixed than in a hand-worked furnace, 
 while the sulphate produced is of a very fine and uniform 
 character.' Although at present the charge is intro- 
 duced and withdrawn by hand, Mr. Goodman hopes to 
 perfect a plan for doing this by machinery. 
 
88 THE ALKALI TRADE. 
 
 The advantages claimed for the use of this new furnace 
 may be stated as follow : (1) A more regular means of 
 working, and exemption from breakages. (2) A saving in 
 wages, one man only being required for each shift for 
 charging and working the furnace. (3) A saving of fuel. 
 In the ordinary method 9 cwt. of coal (equal to 5.^ cwt. 
 of coke) are consumed per ton of sulphate turned out, 
 whereas by this method only 3 cwt. coke are used per 
 ton of salt-cake made. (4) A calculated saving in sul- 
 phuric acid, amounting to about 2 per cent. (5) The 
 hydrochloric acid is generated regularly and of an uniform 
 strength throughout, which allows of its perfect con- 
 densation in one tower, giving acid, which, when hot, 
 marks 26 to 28 T. Finally, there appeared good 
 reason to expect that each furnace would turn out 100 
 tons of sulphate of sodium weekly, but more recent ex- 
 periences have not fulfilled, we believe, the expectations 
 formed in regard to this plant. 
 
 From what has gone before, it will be evident that 
 the maximum amount of sulphuric acid that is manufac- 
 tured is employed as a means of decomposing salt, with 
 the production of a material to be afterwards used 
 (when not for glass-making) for obtaining caustic and 
 carbonated soda. Therefore the saving that would be 
 effected by the introduction of a process (supposing it to 
 be effectual) for making c salt-cake ' in one operation, and 
 thus abolishing the necessity for costly acid chambers, is 
 enormous, and at once evident. Of the many methods 
 suggested, previous to Hargreaves' (of which more anon), 
 the most plausible was that of Longmaid, which though 
 not entirely new, being based on a well-known reaction, 
 was greatly developed and the method of working im- 
 
LOXGMAID'S AKD HARGREAVES' PROCESSES. 89 
 
 proved by him. So late as 1861, the process was in use 
 at several works, but it has never been in general or 
 even extensive, use, on account of a loss of sulphurous 
 acid which is experienced. This process consists in 
 roasting pyrites and salt in a reverberatory furnace, 
 sulphate of sodium, ferric oxide and chlorine being the 
 products: 4 FeS 2 + 10 NaCl + 190 2 = 2 Fe 2 3 4- 8 lX T a 2 S0 4 
 + 8 C1 2 (Miller). From the residue, the sulphate of 
 sodium is extracted by lixiviation, and the residual ore 
 worked for copper, silver, and iron. Some chlorine is 
 evolved likewise, but it is too dilute to make good 
 c bleach ' to which purpose Longmaid proposed to direct 
 it, after washing out the hydrochloric acid which itself 
 was'contaminated with volatile ferric chloride. 
 
 During the last few years, Mr. Hargreaves, of Widnes, 
 has worked out a process for the direct manufacture of 
 sulphate of sodium, which consists in exposing common 
 salt, moulded into bricks or other forms with a little 
 water, to the action of sulphurous acid, air and steam, 
 at a temperature of 800 to 900 Fahr. The fol- 
 lowing reaction first sets in at about 700 Fahr., 
 2NaCl + S0 2 + + H 2 = Na 2 S0 4 + 2HC1. The salt is 
 placed in the chambers, and finished sulphate is drawn 
 out. Mr. Hargreaves has stated that the loss of sulphurous 
 acid experienced is much less than in the old process, and 
 that a part of the hydrochloric acid is ' burned ' into chlo- 
 rine and water. But this last statement as to the chlorine 
 is of no value, because much chlorine could not be formed, 
 and none could permanently exist in the presence of 
 sulphurous acid, whilst if any existed it would simply be 
 an inconvenience when in small quantity. The gases 
 from the pyrites burners constitute the sulphurous acid 
 
 F THE 
 
90 THE ALKALI TRADE. 
 
 employed, and these being at a red heat, and the action 
 itself being a source of heat ' the fuel required to make 
 a ton of sulphate is not more than a third part of that 
 required by the sulphuric-acid process of making salt- 
 cake.' One most important feature in the process is that 
 it dispenses with the use of nitrate of sodium, which is 
 costly, and rock-salt can be employed. Further, as no 
 very high temperatures are employed, the wear and tear 
 of the apparatus is quite inappreciable. Some time 
 since (March 1874), we were informed that two 
 manufacturers were building plant for the production of 
 100 tons of salt-cake per week each, and that a third 
 plant was about to be commenced. Moreover, Mr. Har- 
 greaves has for some time prepared considerable quan- 
 tities of salt-cake by his method. At any rate it is of 
 very high importance, and bids fair to attain commercial 
 success. 
 
 This statement is supported by the fact that quite 
 recently two patents have been secured relative to this 
 process. In one, Mr. Arthur McDougall proposes to use 
 superheated steam, by which means he claims to complete 
 the reaction in less time. He also claims to facilitate the 
 reaction by maintaining the salt in motion by suitable 
 means, and thus avoids the moulding of the salt into 
 bricks. In the other, Mr. William Hunt proposes to 
 erect the chambers wherein the decomposition is effected, 
 immediately over the pyrites burners, so that the heat 
 from the hot gases issuing therefrom is utilised, as far as 
 practicable, to heat the contents of the chamber itself. 
 Eobb, in 1853, had proposed to pass sulphurous acid, air 
 and steam over salt and oxide of iron ; and even more, 
 in 1857 Brooman passed these gases over salt alone, 
 
HARGREAVES' PROCESS DESCRIBED. 91 
 
 contained in hot flues. But it was left, as we have 
 seen, for Mr. Hargreaves to develope the process as a 
 manufacture. 
 
 Phillips and Kuhlmann, in 1832, proposed to make 
 sulphurous acid into sulphuric acid by passing it, along 
 with hot air, over finely divided platinum; and in 1855, 
 Schmersahl and Bouck passed a mixture of sulphurous 
 acid, air and steam through horizontal pipes of clay or 
 iron, filled with asbestos, pumice or other porous mate- 
 rial, and strongly heated in a furnace. But this last 
 method was probably an outgrowth from Wohler's 
 researches (' Ann. Chem. Pharm.,' Ixxxi. 255), to which 
 we have already adverted, and which demonstrated the 
 facility with which the oxides of copper, iron, and chro- 
 mium, at a low red heat, transform sulphurous acid and 
 oxygen into sulphuric acid. But, as previously stated , the 
 attempts that were made at Oker on a large scale proved 
 unsatisfactory. Hargreaves' process, then, combines the 
 principles involved in those processes, just briefly sketched, 
 and goes a step further, and presents to the sulphuric 
 acid at the moment of formation common salt where- 
 upon to react. This, no doubt, aids moreover the for- 
 mation of the sulphuric acid. 
 
 Having now given an outline of Hargreaves' pro- 
 cess, and of certain older proposals, which seem to lead 
 naturally to it, we purpose considering more in detail the 
 precise method of procedure. In doing this, we are 
 greatly helped by the drawings kindly placed at our 
 disposal by Mr. Hargreaves, and which we reproduce 
 here (figs. 13 and 14). Originally, Mr. Hargreaves 
 moulded the salt into bricks with water, these when dry, 
 were broken into pieces about 1^ inch in diameter. 
 
92 THE ALKALI TRADE. 
 
 But, more recently, Mr. J. C. Stevenson has invented an 
 apparatus for moulding the salt into pieces of suitable 
 size and shape (circular), which are then dried by causing 
 them to traverse the length of an oven like those used by 
 biscuit bakers. The advantages of using salt prepared in 
 this form consist in the saving of labour by the use of 
 machinery ; avoiding the production of dust in the break- 
 ing machine ; saving fuel, and ensuring regularity of 
 action by uniformity of the pieces of salt in size and 
 shape. Mr. Hargreaves prefers to use ' coal salt,' that is 
 to say, salt obtained by surface evaporation of brine 
 liquors by the direct action of flame, as, by these means, 
 salt is obtained which binds better and preserves a poro- 
 sity. And in a recent paper he states that he has received 
 much assistance through Pohl's process of making salt, 
 which, by a considerable reduction in the fuel, reduces 
 the cost of the salt. 
 
 The sulphurous acid gas used in the process is of 
 course derived from the roasting of pyrites, but, inasmuch 
 as the success of the whole process depends on the amount 
 of fuel used, Mr. Hargreaves does not use the ordinary 
 form of burner, but one which avoids the loss of heat 
 experienced generally through radiation from the burner 
 front. This is effected by encasing the door in a non- 
 conducting lining, and avoiding the exposure of surfaces 
 of iron to the heat of the burning pyrites, by substituting 
 common brickwork, which forms en excellent non-con- 
 ducting material. 
 
 Mr. Hargreaves describes the plan of working as 
 follows : 
 
 6 The prepared salt is placed in iron cylinders where 
 it lies without further manipulation till converted into 
 
SCALE 
 
 PLANT USED IN HARGREAVES' 
 
C \'/ CAS FLUE 
 
 7-'K 
 
 TO I FT | 
 
 BSS FOR MAKING SALT-CAKE 
 
IZ" OF SALT 
 
 GROUND 
 LEVEL 
 
 1 
 
 L 
 
 FIRE PLACE 
 
 CROSS 
 
 ASH PIT 
 
 HAEGREAVES' PLANT 
 
GHOUNCi 
 LEVEL 
 
 I MAKING SALT-CAKE. 
 
HARGREAVES' PLANT. 93 
 
 sulphate. The minimum number of cylinders that we 
 advise is eight in a series, and the greater the number 
 the more regular is the reaction, and the smaller the 
 quantity of fuel required per ton of sulphate manufactured. 
 The series of cylinders is so arranged that each in its 
 turn becomes the first, intermediate, and last. The S0 2 is 
 first admitted into the cylinder whose contents are most 
 nearly converted into sulphate, and the spent gases pass 
 out from that which was last charged with salt, after 
 passing through a succession of cylinders containing less 
 and less sulphate.' 
 
 6 The apparatus here shown consists of eight cylinders 
 of 15 feet diameter and 12 feet high, disposed in two 
 rows and marked AT, A2, etc. They are provided with 
 doors, B, for withdrawing the sulphate. The ground 
 space between the two rows of cylinders is covered by an 
 arch which is covered with ashes. Along the sides of 
 the two rows of cylinders, and over the abutment of the 
 arch, are two iron flues, C, which conduct the S0 2 from 
 the burners to the cylinders. The flues are protected 
 from loss of heat by the arch below and a bulk of ashes 
 on the outside, the other side being against the heated 
 cylinder. A layer of ashes is also laid over the flues. 
 Ashes form the most efficient non-conducting material 
 readily obtainable, their rate of conduction being only 
 about half that of common bricks, and being also costless 
 and of small weight for a given bulk. Each sulphurous 
 acid flue has four syphons, D, connecting them with each 
 of the cylinders. The cylinders are connected with each 
 other by the circulating syphons, E. When at work the 
 whole of the S0 2 syphons, except the one connected with 
 the ' finishing ' cylinder (i.e. the cylinder whose contents 
 
94 THE ALKALI TRADE. 
 
 are most nearly converted into sulphate), are closed, and 
 the S0 2 is allowed to flow into this cylinder. Suppose 
 A3 to be the finishing cylinder and A2 the exit cylinder, 
 the S0 2 syphon between C and A3 is open and the circu- 
 lating syphon between A3 and A2 closed, so as to pre- 
 vent the S0 2 from passing direct to the exit cylinder 
 without going through the whole series. The gas passes 
 in succession through A3, 4, 5, 6, 7, 8, 1 and 2 leaving 
 the cylinders by an opening in the bottom of the drawing 
 doorway, F, whence it passes into the flue, G, and is 
 withdrawn by exhausting apparatus. The salt or sul- 
 phate lies upon moveable grids, H, which are supported 
 by tripods. These tripods fall readily on striking out 
 small cramps which keep the feet near together, and 
 leave the grids unsupported when the sulphate is with- 
 drawn. When the sulphate in A3 is finished the gas is 
 admitted into A4 from the S0 2 flue, the circulating 
 syphon between A4 and A3 is closed. After withdraw- 
 ing the sulphate and filling A3 with salt, the circulating 
 syphon between A2 and A3 is opened and A3 is made 
 the exit cylinder. The short pipes, J, serve as charging 
 holes to supply the charge of salt. One of these has an 
 annular space around it, to admit the products of com- 
 bustion into the inside of the cylinder, if at any time it is 
 desirable to heat the salt before turning the gases into it. 
 It also allows any gases from the inside of the cylinder to 
 pass directly into the chimney flue, and prevent them from 
 annoying the workmen when withdrawing the charge. 
 
 6 The ' gas from the pyrites kilns is too concentrated 
 to be allowed to pass direct into the cylinders containing 
 raw salt, for then the action becomes so violent as to fuse 
 it into a hard cohesive mass. This is avoided by getting 
 
WORKING RESULTS OF HARGREAVES' PROCESS. 95 
 
 up the temperature as soon as possible, arid allowing the 
 salt to get covered with a coating of sulphate while at 
 the exit end of the series, where only about one-tenth of 
 the original quantity of S0 2 is contained in the gas. The 
 covering of sulphate increases in thickness as the cylinder 
 gets nearer the inlet.' 
 
 1 The cylinders are heated by fire-places (1). The 
 hot gases pass through a horizontal flue (2) and ascend 
 narrow vertical flues ; these flues are only 5 inches square 
 in section, the object being to reduce the heat-absorbing 
 surface where the products of combustion are very hot ; 
 the flues, however, are amply large enough to carry away 
 all the products of combustion. The fire-places are fur- 
 nished with close-fitting doors, so that when the fires are 
 not needed, both the fire-places and ash-pits may be 
 secured against admission of air, and at the same time the 
 damper (4) is closed to stop draught to the chimney. 
 After leaving the vertical flues the smoke passes into a 
 space 10 inches deep between the cylinder cover and an 
 upper covering plate, circulating round the charging 
 holes and over the cylinder cover ; the smoke then passes 
 down the side of the cylinder and beneath it, when it 
 passes the damper to the chimney.' 
 
 The amount of fuel consumed at Messrs. Boyd and 
 Alexander's is as follows, viz. : 
 
 Heating cylinders . . .4 cwt. \ 
 
 Preparing salt . 3 Per ton of sulphate 
 
 Steam, say ... j of sodium> 
 
 Total . . . 7|cwtJ 
 
 The following is an analysis by Mr. W. Plunkett of 
 an average sample of a cargo shipped by Messrs. Boyd 
 and Alexander : 
 
96 THE ALKALI TRADE. 
 
 Sulphate of soda ..... 
 Chloride of sodium .... 
 
 Free acid and moisture .... 
 Oxide of iron and insoluble 
 
 Total 100-00 
 
 Mr. Hargreaves, by dint of very difficult and pro- 
 longed studies, has at last succeeded in placing the pro- 
 cess on such a basis as to form a powerful rival to the 
 old method of working. In short, there can be no doubt 
 that if in the future the process should meet with that 
 success which is expected of it, it will amount to a com- 
 plete revolution in the alkali trade of this country. 
 
 Of many other processes that may have been proposed, 
 or used to a small extent, for the manufacture of sulphate 
 of sodium, the following are the only ones it is desirable to 
 mention here. M. Eamon de Luna has shown that when 
 crystallised magnesium sulphate (Epsom salts), which 
 abounds in certain Spanish mines, and which is also a 
 manufactured product from Greek stone (MgC0 8 ) and 
 sulphuric acid, is heated to redness with half its weight 
 of salt, hydrochloric acid is evolved, and magnesia and 
 sulphate of sodium are left. Indeed, by this process, 
 more than 12,000 kilos, of very pure sulphate of sodium 
 have been made. The MgO can of course be used over 
 again by dissolving it in sulphuric acid. In 1871 Mr. 
 Henry Deacon secured by patent a process for producing 
 sulphate of sodium simultaneously with chlorine, by the 
 passage of sulphuric anhydride (S0 3 ) mixed with air or 
 oxygen, over or through chloride of sodium at an ele- 
 vated temperature ; the following reaction first occurs : 
 2NaCl + 2S0 8 = Na 3 S0 4 ,+ SO a + Cl 3 . Thus, as will be 
 seen, sulphurous acid is produced along with the chlorine, 
 
MANUFACTURE OF GLAUBER'S SALTS. 97 
 
 and of course the latter cannot be used for the produc- 
 tion of bleaching powder until after the removal of the 
 sulphurous acid. Mr. Deacon proposes to effect this re- 
 moval, by causing the sulphurous anhydride to become 
 sulphuric anhydride by uniting it with oxygen of the 
 air present, through the catalytic action (so called) of 
 sulphate of copper, or other substances. Then this sul- 
 phuric anhydride is passed over other chloride of sodium, 
 thus giving more sulphate of sodium and half the original 
 quantity of sulphurous acid. The apparatus is so arranged, 
 therefore, that the gases pass alternately over sodic chloride 
 and the catalytic substance ; and by repetition of these pro- 
 ceedings Mr. Deacon claims to convert all the sulphurous 
 acid into sulphate of sodium, with the liberation of the 
 chlorine from the salt in a state of dilution with the 
 nitrogen of the air, etc. In a somewhat later patent Mr. 
 Deacon describes a process very much like the foregoing, 
 but distinct in several particulars. It consists in passing 
 sulphurous acid, air, and aqueous vapour at an elevated 
 temperature over heated salt, giving sulphate of sodium 
 and hydrochloric acid thus: 2Nad + S0 2 + H 2 + = 
 Na 2 S0 4 + 2HC1. The hydrochloric acid gas and the ex- 
 cess of air are then exposed to the influence of sulphate 
 of copper or other substance at a high temperature, 
 giving dilute chlorine to be utilised by any existing pro- 
 cesses for the production of bleaching powder (2HC1 + O 
 =H 2 + C1 2 ). 
 
 Glauber's salts is the name for sulphate of sodium 
 which has been further refined by recrystallisation, and 
 this manufacture is carried on at several works in Lanca- 
 shire ; but the substance so obtained is not sold in any 
 
 H 
 
98 THE ALKALI TRADE. 
 
 great quantity. Of course, when sulphate of sodium is 
 obtained by the methods heretofore described, it is in 
 an anhydrous state ; but on r eery stall! sation it combines 
 with water of crystallisation, and has the formula Na 2 S0 4 , 
 10H 2 0. 
 
PRODUCTION OF BLACK ASH. 99 
 
 CHAPTEE VII. 
 
 MANUFACTURE OF CARBONATE AND BICARBONATE OF SODIUM. 
 
 THERE are several varieties of commercial sodium car- 
 bonate, which are known respectively as soda ash, white 
 alkali, and soda crystals, and which differ in form and 
 their degree of purity. But they are all produced from 
 4 black ash,' which is crude sodic carbonate, made by fur- 
 nacing sodium sulphate together with chalk or limestone 
 or lime, and coal. The proportions in which these several 
 substances are mixed are almost identical with those first 
 used by Le Blanc ; and although each manufacturer has 
 his peculiar idea of the best proportions, it may safely be 
 said that those usually employed are as follow : Salt- 
 cake (sulphate of sodium), 3 cwt. ; chalk or lime, 3 cwt, ; 
 coal (slack), 1-5 to 2 cwt. These figures represent the 
 actual weights employed where, as is the more usual 
 practice, ' twenty-four stone balls ' are made. This ex- 
 pression signifies that twenty- four stone salt-cake has been 
 actually employed in making each ' ball ' ; but in some 
 works ' twenty-stone balls ' are made, or, in other words, 
 while the proportions observed in the mixing are the same 
 as those above given, the quantities start from 2-5 cwt. 
 of salt-cake. When caustic soda constitutes the desired 
 product, the proportions used are different to those given, 
 and certain other conditions are also observed ; but these 
 will be pointed out fully in our next chapter. 
 
 Before proceeding to describe the operations which 
 
100 
 
 THE ALKALI TRADE. 
 
 are undertaken to produce carbonate of sodium from 
 such mixtures, we will quote a few analyses of salt-cake, 
 limestone, and slack ashes made by Mr. George E Davis. 
 
 Analyses of Salt-cake. 
 
 Constituents 
 
 A 
 
 B 
 
 c 
 
 Insoluble in water 
 
 0-112 
 
 0-073 
 
 0-042 
 
 Free sulphuric acid . 
 Calcium sulphate 
 Iron persulphate , 
 Sodium chloride 
 
 0-955 
 1-139 
 
 0-682 
 2-632 
 
 1-820 
 1-148 
 0-588 
 0-234 
 
 0-022 
 1-046 
 0-322 
 0-744 
 
 Sodium sulphate 
 Moisture .... 
 
 94-393 
 
 0-087 
 
 96-137 
 
 97-824 
 
 100-00 
 
 100-00 
 
 100-00 
 
 Analyses of Lump Limestone. 
 
 Constituents 
 
 Euxton. 
 
 Minera. 
 
 Ruthin. 
 
 Organic matter . 
 Silica .... 
 
 traces 
 0-106 
 
 traces 
 0-442 
 
 traces 
 
 0-398 
 
 Alumina .... 
 
 0-123 
 
 0-145 
 
 0-135 
 
 Ferrous carbonate 
 
 0-187 
 
 0-348 
 
 0-252 
 
 Calcium carbonate 
 
 99-372 
 
 98-298 
 
 98-370 
 
 Magnesium 
 Manganese 
 Calcium phosphate 
 
 0-116 
 0-013 
 trace 
 
 0-756 
 0-022 
 trace 
 
 0-756 
 0-026 
 trace 
 
 99-917 
 
 100-011 
 
 99-937 
 
 Analyses of Ashes of Slack. 
 
 Constituents 
 
 A 
 
 B 
 
 Silica . 
 
 
 
 49-36 
 
 48-74 
 
 Alumina 
 
 .... 
 
 26-86 
 
 22-79 
 
 Iron peroxide 
 Lime . 
 
 
 
 14-00 
 7-07 
 
 18-76 
 5-43 
 
 Magnesia ...... 
 Sulphuric acid (S0 3 ) .... 
 Phosphoric acid (P 2 5 ) 
 
 0-48 
 1-12 
 0-11 
 
 0-99 
 
 2-74 
 0-05 
 
 99-00 
 
 99-50 
 
BLACK ASH FURNACES. 101 
 
 As regards the sulphate of sodium, it may be said 
 that since the introduction of improved methods of manu- 
 facture, such as those described in our last chapter, it is 
 easily obtained of even greater purity than that indi- 
 cated by the above analyses. 
 
 The limestones as supplied to the works are often 
 mixed up with a quantity of clay or sand, which matters 
 increase the silica and alumina introduced into the pro- 
 cesses to be described, and act prejudicially by causing 
 a loss of sodium as insoluble salts. Mixing slack yields 
 from 7 to 16 per cent, ash, and from the above analyses 
 it will be seen how much silica and alumina is -introduced 
 in this way ; therefore, the lower the percentage of ash 
 the better fitted is the coal for its purpose. The per- 
 centage of carbon present in the various varieties of slack 
 varies from 70 to 88 per cent, more or less. But to con- 
 tinue the study of the process of soda manufacture. The 
 salt-cake, limestone, and slack are worked by a spade 
 into a mixture which should be free from large pieces, 
 and in this state it is charged into the furnace. 
 
 The reverberatory furnace used, is provided with two 
 beds, one of which is at a lower level than the other. 
 The one nearest the fire is the lower one, while the charge 
 is introduced on the furthest one from the fire, through 
 an iron door. Thus two charges, each of about 7 cwt., 
 are in work at a time, one heating, and one fluxing on 
 the hottest bed. Towards the end of the operation much 
 gas (chiefly carbonic oxide) is evolved in the form of 
 ' candles,' which burn with a yellowish- green flame. At 
 this stage tranquil fusion sets in, and the operation is 
 completed. It is therefore raked out, after a little brisk 
 working, into ' bogies,' which are square iron boxes about 
 
102 THE ALKALI TRADE. 
 
 9 inches deep, set on wheels. When cold the product 
 is known as ' ball-soda,' and each ball weighs about 
 5 cwt., twelve to sixteen being produced in twelve hours. 
 
 These balls consist of carbonate of sodium and caustic 
 soda, sulphide and carbonate of calcium, unburned coal, 
 etc. They contain from 22 to 26 per cent, alkali, 
 reckoned as Na 2 ; from 0'5 to 1*0 per cent. Na 2 S0 4 and 
 0*6 to I'O per cent. Na 2 S when properly made. It is 
 easy to see by their colour when they are ' overlimed,' and 
 in such a case the balls, by losing much of their porosity, 
 yields less alkali in the vats. By ' green balls ' is meant 
 under-roasted balls containing an excess of undecom- 
 posed sulphate, and ' burnt balls ' signifies over-roasted 
 balls, which are generally pregnant with sulphides of 
 sodium. Analyses of black ash necessarily differ widely, 
 as it is not a pure chemical individual; moreover, the 
 analyses of the different samples of the same ball often 
 differ considerably. 
 
 The elaborate analyses of black ash or ball soda stated 
 on p. 103, were given by Mr. G. E. Davis in a paper on 
 the manufacture of white caustic soda read before the 
 Society for the Promotion of Scientific Industry, May 25, 
 1875. 
 
 In these analyses Mr. Davis has calculated the matters 
 into soluble and insoluble constituents, so that it may be 
 readily seen what dissolves and what remains insoluble 
 during the subsequent process of lixiviation. 
 
 The general results which are there indicated, fairly 
 express those obtained by the author also, during an 
 investigation of the chemistry of black ash making, 
 extending over many months. It will be seen from these 
 analyses how difficult must be the methods employed. 
 
COMPOSITION OF BLACK ASH. 
 
 103 
 
 The analytical methods ordinarily employed in the 
 analysis of black ash serve only to yield results which 
 are valuable, so far as they admit of comparison among 
 themselves, while, in many instances, the actual results 
 obtained are not to be trusted. We hope that Mr. G. 
 E. Davis will soon find time to elaborate and publish his 
 new methods of analysis. 
 
 Constituents 
 
 A 
 
 B 
 
 c 
 
 Sodium carbonate 
 
 28-144 
 
 31-807 
 
 28-336 
 
 oxide 
 
 5-860 
 
 5-614 
 
 3-844 
 
 chloride . 
 
 2-808 
 
 2-574 
 
 3-101 
 
 sulphate . 
 
 0-192 
 
 0-191 
 
 3-037 
 
 sulphite . 
 
 0-151 
 
 0-072 
 
 none 
 
 hyposulphite 
 
 0-189 
 
 0-853 
 
 0-126 
 
 sulphide . 
 
 0-358 
 
 0-163 
 
 6-645 
 
 aluminate 
 
 0-344 
 
 0-752 
 
 0-923 
 
 silicate 
 
 1-026 
 
 0-914 
 
 0-758 
 
 cyanide . 
 
 0-186 
 
 0-043 
 
 0-422 
 
 sulphocyanide 
 
 0-074 
 
 0-021 
 
 0-077 
 
 Calcium sulphide 
 
 29-504 
 
 29-744 
 
 33-245 
 
 carbonate 
 
 12-657 
 
 9-272 
 
 6-087 
 
 oxide 
 
 10-048 
 
 9-488 
 
 3-465 
 
 Iron sulphide 
 
 0-554 
 
 0-774 
 
 1-355 
 
 Alumina 
 
 0-172 
 
 1-042 
 
 0-624 
 
 Silica . 
 
 1-095 
 
 0-923 
 
 0-973 
 
 Magnesia 
 
 0-266 
 
 0-322 
 
 0-146 
 
 Soda . 
 
 0-344 
 
 0-546 
 
 0-577 
 
 Carbon 
 
 4-263 
 
 4-483 
 
 4-958 
 
 Sand . 
 
 1-237 
 
 0-875 
 
 0-842 
 
 
 99-472 
 
 99-479 
 
 99-646 
 
 Soluble iron sulphide . 
 
 
 
 105 
 
 All that has gone before, relates to hand-worked fur- 
 naces. These are subject to great wear and tear, which 
 destructive processes display themselves equally on 
 the tools employed by the workmen for raking and 
 stirring the mixture. There is also experienced a large 
 absorption of the fused mass into the bed of the fur- 
 
 01 
 
104 THE ALKALI TRADE. 
 
 nace, and in this way the furnace is often destroyed by 
 actually fusing through into the fireplace where the 
 heat is the greatest. To avoid this difficulty, air-pas- 
 sages are sometimes constructed between the fireplace 
 and the first bed of the furnace. Moreover, these fur- 
 naces have to be stopped at definite periods in order 
 that the flues may be cleaned out. The loss caused by 
 stoppage might, perhaps, be avoided by constructing the 
 furnace with two flues ultimately converging and pro- 
 vided with swing dampers, so that the one flue might be 
 used while the other is being cleaned out. 
 
 We must now direct our attention to a form of fur- 
 nace which was first introduced in 1853. Already, in 
 1848, Mr. W. W. Patinson had devised a furnace in 
 which the balls were worked and expelled by machinery, 
 but it was short lived on account of the great wear and 
 tear incidental to the use of such high temperatures. 
 The first form of revolving furnace worked very indif- 
 ferently ; the balls turned out by it were not sufficiently 
 porous, and therefore would not lixiviate well. But 
 shortly afterwards Messrs. Stephenson and Williamson, 
 of the Jarrow Chemical Works, effected an improvement 
 in its construction, which again led to its use. Since then, 
 many other improvements have been introduced, among 
 others by Messrs. Robert Daglish and Co., to whose 
 courtesy we are again indebted for the engravings of a 
 revolving furnace (figs. 15, 16, and 17). This furnace is 
 worked with Siemens' patent gas arrangement, and on con- 
 sulting the references attached to the figures, the methods 
 of heating and working will be evident to the reader. The 
 furnace itself is cylindrical, and is lined with fire-bricks, 
 ridges of which project one above the other, and act as 
 
1 
 
 1 
 
 
 1 
 
 ^ 
 
 1 
 
 t 
 
 ' 
 
 9 1 
 
 1 
 1 
 
 1 
 
 N 
 
 1 
 
 1 
 1 
 1 
 1 
 
 1 
 
 
 D 
 
 B 
 
 c -' 
 
 ] 
 
 REVOLVING FURNACE F 
 
 
 
 
 REVOLVING FURNACE FOR 
 
Si 
 51 
 
 AKING BLACK ASH (PLAN). 
 16. 
 
 , ; -'< I - 
 
 ^^,^/.^--^io-^.^r^v.--v>;^--:v:vt:-^ r :./'^^^^^ 
 
 SSjN-^^^rf-^fr,?/^ r^.-.t^s- :A^;^-^7^.-.v^; >^^vx^v-^.^^vv.^^^':,-^^^>;t;^ 
 
 G BLACK ASH (ELEVATION). 
 
REVOLVING FURNACES. 
 
 105 
 
 s 
 
 i I 
 
 I s 
 1. S 
 
 111 
 
 !^ ^ * .o S ^ 
 C * 'C a o> 
 
 8 1 1 ft -g 
 
 1=S^I ^ 9 
 
 % iiifi 5 & 
 
 ^ a l^3 ^ I 
 
 IS 1*111 I 
 
 I }!!!! ! 
 
 I ilflllli I 
 
 ili-PislJt 
 
 ilJFJ fllpl 
 
 ? cs tEcS ll. 5 12 * ? "3 
 
 3 ?fi 
 
106 THE ALKALI TRADE. 
 
 stirrers and mixers. The flame passes into, and around 
 the inside of the furnace, and thence over the liquors 
 requiring concentration, contained in adjacent pans. 
 
 The charge usually employed, consists of 30 cwt. salt- 
 cake, 32 cwt. of limestone, and 20 or 21 cwt. of slack. 
 These are introduced through a hopper, which serves also 
 the purpose of a discharging mouth. Such a charge takes 
 about two hours to work off, and yields ten balls of 
 3 cwt. each. 
 
 The rate at which the furnace revolves at first, is very 
 slow about one revolution per 20 minutes but this 
 can be increased at will, by increasing the speed of the 
 engine, to five or six revolutions per minute, which re- 
 presents the maximum speed. These furnaces are about 
 10 feet in diameter by 15 feet long, but some are now 
 made 12 feet in diameter and 18 feet long. A furnace 
 10 feet by 15 feet is capable of converting about 170 
 tons of sulphate of sodium in six days. 
 
 The advantages gained by the use of revolving fur- 
 naces may be stated thus: (1.) Uniform heating of the 
 charge, and so prevention of loss of sodium by volatilisa- 
 tion. (2.) Less labour is required and more work done 
 in a given time than can be accomplished in an ordinary 
 reverberatory furnace. (3.) The use of tools is rendered 
 unnecessary, and the danger of absorption of soda into 
 the bed of the furnace is obviated. One disadvantage 
 of the use of these revolving furnaces is, that they turn 
 out balls which are somewhat dense, and therefore 
 difficult to thoroughly lixiviate. 
 
 This led to the carbonate of lime and part of the coal 
 being first charged and heated for some time, so as to 
 produce a quantity of caustic lime, the other materials 
 
MACTEAE'S IMPROVEMENTS. 107 
 
 being added subsequently. In this method the obtained 
 results are better. The plan of charging a mixture of 
 caustic lime and carbonate of lime with the sulphate of 
 soda and coal, has also been tried, but gave balls bad 
 in quality and difficult to dissolve. Mr. James Mactear, 
 aware of, and used to these difficulties encountered in 
 making ball soda in revolving furnaces, has patented 
 improvements, which are in work most successfully, 
 both at St. Eollox, Glasgow, and in the Lancashire 
 district. 
 
 In the working of these improvements, a mixture 
 of sulphate of soda with coal, and a quantity of car- 
 bonate of lime barely in excess of the chemical equivalent, 
 is charged at one time into the revolving furnace, and the 
 heating operation is allowed to proceed until the reaction 
 is nearly complete, which is recognisable by the fluxing 
 of the materials and other signs. At this point, a small 
 quantity, say 10 per cent., of crushed caustic lime is 
 added, and then, as soon as this added caustic lime is 
 thoroughly mixed with the other materials, the entire 
 charge is withdrawn. In this way the disadvantage of 
 having caustic lime present during the reaction is avoided, 
 whilst the intermixture of a suitable small proportion of 
 caustic lime at, or near the end, has the effect of render- 
 ing the resulting balls easily soluble, and well conditioned 
 for the subsequent operations. The quantity of caustic 
 lime to be thus added 'will vary accordingly as the manu- 
 facturer wishes to have more or less of the soda in a 
 caustic state, 3 to 4 per cent, having in practice given 
 good results in cases in which a minimum proportion of 
 caustic soda was desired.' 
 
 Among the advantages attending these improvements, 
 
108 THE ALKALI TRADE. 
 
 the following are enumerated by Mr. Mactear : (1.) The 
 proportion of carbonate of lime being diminished, a much 
 increased quantity of sulphate of soda may be decom- 
 posed in a furnace of a given size ; in fact, the productive 
 power of these furnaces is thus increased by 50 per cent. 
 (2.) The time occupied in finishing each charge being re- 
 duced, an increased number of charges can in most cases 
 be worked in a given time. (3.) There is a great saving 
 of coal and carbonate of lime. (4.) A diminished propor- 
 tion of waste is left on lixiviating, and consequently less 
 soda is lost with the waste. (5.) A diminished proportion 
 of caustic soda and sulphides are found in the liquors, the 
 total caustic lime being alterable at pleasure.' 
 
 Now we shall see that Kestner has demonstrated that 
 in making black ash the loss of soda as insoluble salts in 
 waste, increases with the increase of proportion of car- 
 bonate of lime used, and he recommends, therefore, the use 
 of the least possible excess. Mr. Mactear's improvements 
 are based upon these facts, and by their use lie produces 
 soda at a cheaper rate with less loss. At the same time, 
 by introducing a percentage of lime near the end of the 
 operation, the porosity of the ball is not sacrificed, and 
 so perfect lixiviation is ensured. 
 
 In December, 1876, nineteen revolvers were working 
 according to this improved process, and Mr. Mactear 
 anticipated that by the following January twenty more 
 would be working. This fact is not surprising in face of 
 the splendid results obtained by the use of these improve- 
 ments. 
 
 The chemical reactions that occur in the furnace have 
 been made the subject of much discussion and experiment. 
 We shall content ourselves here, with stating Mr. Gossage's 
 
LOSSES OF SODA IX LEBLANC'S PROCESS. 109 
 
 views, which are those most generally adopted, and which 
 are expressed in the following equation : 
 
 2Na 2 S0 4 + 3CaC0 3 + 9C = 2Na 2 C0 3 + 2CaS + CaO+ 10 CO evolved. 
 
 Perhaps this is the right time to note that Ely the and 
 Kopp patented and worked a balling process, in which 
 peroxide of iron was used instead of lime or chalk. The 
 sulphide of iron so obtained was burned to furnish fresh 
 sulphurous acid for the chambers, whilst the residual 
 ferric oxide was used over and over again. 
 
 We must next consider the losses of soda that are ex- 
 perienced in the ' balling operation ' as conducted in hand- 
 worked furnaces. Dr. C. E. A. Wright estimates the losses 
 as follows : 
 
 Undecomposed sodic sulphate . .3*49 per cent. 
 Insoluble sodic compounds . . .5*44 
 Vaporisation of sodic compounds . . 1'14 
 
 10-07 
 
 These results were based on experiments conducted 
 during the manufacture of 5,000 tons soda ash. 
 
 M. A. Scheurer-Kestner claims to have proved that in 
 the furnacing operation, no soda-salts are reduced to 
 metallic sodium, and therefore no loss by volatilisation 
 of the metal occurs ; and that the greater part of the loss 
 is due to the formation of insoluble sodic salts, which 
 are retained in the waste, a loss which is never less 
 than 5 per cent., and often greater. He endeavours to 
 show that this loss increases proportionately with the 
 excess of limestone or chalk employed, inasmuch as this 
 excess of lime becomes hydrated in the vats, and reacting 
 upon the Na 2 C0 3 forms insoluble salts. He gives the fol- 
 lowing table : 
 
110 THE ALKALI TRADE. 
 
 Limestone used for 100 Na,S0 4 Na retained by 100 waste. 
 
 98-0 0-59 
 
 102-0 0-86 
 
 107-5 1-27 
 
 111-0 1-30 
 
 Whilst, therefore, an excess of lime is generally used 
 to prevent the formation of polysulphide of calcium, 
 Kestner recommends the use of no excess, or the least 
 possible, to avoid loss of soda as insoluble salts. 
 
 In a paper already quoted from, by Mr. Mactear, the 
 loss of soda in Leblanc's process is given, and he finds 
 that the greatest loss occurs as insoluble sodic salts plus 
 soluble salts in the waste, which amounts to 5 or 7 per 
 cent, of the total soda. 
 
 The Lixiviation of the Black Ash constitutes the 
 second stage in the manufacture of sodic carbonate. The 
 present system of effecting this operation is mainly due 
 to the efforts of Clement Desormes and Mr. Shanks. 
 Clement Desormes' arrangement embodied the descent of 
 the liquor contained in the top vat of a series arranged 
 one above the other, to those successively below it, and 
 worked the black ash in the opposite direction. That is 
 to say, the black ash, being first introduced into the lower- 
 most vat, was transferred from vat to vat by means of 
 baskets worked with handles, until it reached the highest 
 vat, by which time it was fully exhausted. But it was 
 reserved for Shanks to take advantage of the superior 
 specific gravity of the liquid obtained by lixiviation over 
 that of water. This he did by recognition of the principle 
 that a given column of a liquid of a given specific gravity, 
 corresponds with a given greater column of a liquid of a 
 less specific gravity ; and therefore if a series of vessels be 
 arranged in a row, and contain liquids of the varying 
 
LIXIVIATION OF BLACK ASH. Ill 
 
 specific gravities, which gradually decrease from first to 
 last, a flow is effected from the beginning to the end. just 
 the same as if the vessels were ranged one above the 
 other. 
 
 It is on these principles that the vats in most common 
 use are now worked. These vats are either 6 feet square 
 and 6 feet deep, or, as now often constructed, one whole 
 series are 54 feet long, 11 feet wide, and 5 feet deep. 
 
 The black ash is broken up into big lumps, and these 
 are then charged in the vats which are provided with 
 false bottoms on which the black ash rests. Water is 
 then supplied to them at a temperature of about 120 
 Fahr., but the temperature of the water used varies from 
 90 to 140 Fahr., and well it might, when the tempera- 
 ture in many works is simply guessed at, by feeling the 
 pipe conveying it with the hand. The water is contained 
 in a cistern, where it is raised to the required temperature 
 by blowing steam into it. In the tanks or vats, the 
 black ash swells, disintegrates, and yields up its soluble 
 salts, forming a more or less greenish-blue liquid, which 
 is transferred from one vat to the next, where it becomes 
 stronger by taking up alkali from another lot of black 
 ash, and so on, until it leaves the final vat at a specific 
 gravity of about I 1 3. 
 
 The residue remaining in the vats after perfect extrac- 
 tion, so far as is practicable, contains all the sulphur from 
 the sulphate of sodium used to make the black ash, and 
 a certain amount of soda, varying from 0*3 to 1 per cent. 
 Na 2 0. The water used for lixiviation should not exceed 
 about 120 Fahr., otherwise the calcic sulphide is decom- 
 posed into sulph-hydrate, which is soluble, and hydrate 
 of lime, and the sulph-hydrate immediately reacts on 
 
112 THE ALKALI TRADE. 
 
 the sodic carbonate, giving sodic sulphide and calcic car- 
 bonate. 
 
 The following summary of the action of water upon 
 black-balls is taken from Watts's Dictionary, and is infor- 
 mation derived from Kolb: (1.) A given quantity of 
 crude soda yields very different proportions of caustic 
 soda and sulphide of sodium, according to the quantity 
 and temperature of the water and the time allowed for 
 digestion. (2.) The degree of causticity of the resulting 
 solution is not sensibly affected by the quantity of water, 
 but increases with the time of digestion and temperature. 
 (3.) The quantity of sulphide of sodium increases with the 
 quantity of water, and more particularly with time and 
 temperature. (4.) The decrease in the amount of sodic 
 carbonate not only corresponds to the amount of caustic 
 soda formed, but is also affected by the variation in the 
 amount of sodic sulphide formed. Hence, it would ap- 
 pear that the sodic sulphide is formed at the expense of 
 the carbonate. (5.) The amounts of sulphide and caustic 
 soda formed bear no definite relation one to the other. 
 (6.) The presence of lime or caustic soda prevents the 
 action of sodic carbonate upon calcic sulphide, with the 
 production of calcic carbonate and sodic sulphide. 
 
 The average time required to work off a vat is 
 forty- eight hours. The liquors obtained by lixiviation 
 contain between 10 and 11 Ibs. of real soda per cubic 
 foot, or about 13*5 per cent, by weight. A vat of 
 about 6 feet square conveniently takes twelve balls, and 
 gives liquors of about the following composition, expressed 
 in grammes per litre. The analyses are those of Mr. 
 G. E. Davis. 
 
COMPOSITION OF VAT LIQUORS. 
 
 113 
 
 Analyses of vat liquor 
 
 50 Tw. 
 at 99 Fahr. 
 
 50. 5 Tw. 
 at 90 Fahr. 
 
 Iron sulphide 
 
 
 
 
 
 0-074 
 
 0-042 
 
 Sodium sulphide 
 
 
 
 
 
 4-485 
 
 3-822 
 
 sulphite 
 
 
 
 
 
 1-323 
 
 0-979 
 
 
 hyposulphite 
 
 
 
 
 
 1-580 
 
 1-774 
 
 
 sulphate 
 
 
 
 
 
 12-707 
 
 14-258 
 
 
 chloride 
 
 
 
 
 
 19-597 
 
 23-412 
 
 
 silicate 
 
 
 
 
 
 5-961 
 
 3-774 
 
 
 aluminate . 
 
 
 
 
 
 3-371 
 
 4-218 
 
 
 ferrocyanide 
 
 
 
 
 
 0-133 
 
 0-416 
 
 
 sulphocyanide 
 
 
 
 
 
 0-211 
 
 0-196 
 
 
 phosphate . 
 fluoride 
 
 
 
 } 
 
 traces 
 
 traces 
 
 
 carbonate . 
 
 
 
 
 209-500 
 
 204-326 
 
 hydrate 
 
 
 
 
 
 44-800 
 
 52-740 
 
 It will be seen that these vat liquors contain small 
 quantities of sulphocyanides and ferrocyanides ; they can- 
 not therefore be utilised for furnishing sodic carbonate 
 direct, on account of the yellow colour that adheres to 
 the sodic carbonate in such a case, and which is caused by 
 the presence of iron. 
 
 The destruction of ferrocyanide is said to have been 
 successfully accomplished by Mr. Williamson of the 
 Jarrow Chemical Works, by heating the liquors under 
 pressure to a temperature of 310 Fahr. 
 
 Production of Soda Ash. Where an inferior soda ash 
 is wanted, the vat liquors are boiled down, and the residue 
 calcined in furnaces about 18 feet long and 9 feet wide, 
 and lined internally with fire-bricks. The waste heat 
 from the balling furnaces is generally employed in eva- 
 poration, and in some works the flame is made to pass 
 into a flue running along the top of the furnaces them- 
 selves, and thence downwards into the main flue, whilst 
 on the top of the furnaces are placed pans, the flue being 
 
 i 
 
114 THE ALKALI TRADE. 
 
 constructed as a passage left between the furnace and the 
 pans ; but this method, though very effectual, introduces 
 the evil of a great pressure on the furnace itself, and some- 
 times involves the manufacturer, should his furnace or 
 pans crack or give way, in a mess. Sometimes a system 
 of pans is employed, in the last of which the carbonate of 
 soda deposits, and is sorted out, the mother-liquor being 
 evaporated to dryness. Mr. Gossage, among his multi- 
 farious improvements, aids the evaporation by drawing hot 
 air through the liquors. The product is soda ash, contain- 
 ing from 65 to 73 per cent, carbonate, and from 13 to 24 
 per cent, caustic soda, 4 to 7 per cent, sulphate of soda, 
 and 2 to 6 per cent, of salt, besides small amounts of 
 other substances. 
 
 If required in a purer state (and for the manufacture 
 of plate glass this is necessary) the soda ash is mixed 
 with about its own bulk of sawdust (sometimes small 
 coal is used), and heated in a reverberatory or so-called 
 ' calker furnace,' where it is repeatedly worked by paddles 
 at a temperature of about 600 to 700 Fahr. (about the 
 melting point of lead). Meanwhile the sulphur and 
 carbon are burnt off, and the caustic soda becomes car- 
 bonated. The process is known as ' calking,' and lasts 
 from 2 to 2^ hours. 
 
 For obtaining what is known as white alkali, the 
 soda-ash salts are re-dissolved by water in vats, aided by 
 steam. A ton of water dissolves a ton of the ash, giving 
 a liquor of 54 T., which is allowed to settle, and is then 
 evaporated in iron pans, fired with coke. These pans are 
 20 to 30 feet long, 7 wide, and 2 deep. The ash re- 
 moved is called ' white alkali,' and contains 77 to 84 per 
 cent. Na 2 C0 3 , and from traces to 5 per cent, caustic 
 
SODA ASH AND SODA CRYSTALS. 115 
 
 hydrate ; 2 to 10 per cent, of Na 2 S0 4 ,and 3 to 7 per cent. 
 NaCl. Ward employed Greek stone (Mg C0 3 ) along 
 with the sawdust in carbonating, and he states that in 
 this way, a purer and a stronger white alkali is got. 
 Shanks treated the black ash with carbonic acid, while 
 Wilson patented the use of soda bicarbonate, which he 
 mixed with the liquors in the ordinary reverberatory 
 furnaces, stirring till dry. 
 
 To obviate the presence of sodic sulphide and sul- 
 phide of iron in black-ash liquors, Gossage oxidised the 
 Na 2 S by atmospheric oxidation in towers filled with coke. 
 With such purified liquors the excess of caustic soda must 
 be carbonated by carbonic acid, before boiling down the 
 liquor drawn off from the precipitated ferric sulphide en- 
 suing on the oxidation of the Na, 2 S to Na 2 S0 4 . Gossage 
 further isolated the ferrocyanide present in the liquors by 
 first crystallising out the excess of carbonate, precipitating 
 what remained as bicarbonate, or else causticising it, and 
 crystallising out the potassic ferrocyanide from the mother- 
 liquors, after which it was refined and sold. Mr, Deacon 
 prefers to purify these liquors by means of ferric oxide, 
 which gives ferrous sulphide and caustic soda. 
 
 To obtain the product known as ' soda crystals,' the 
 ' soda ash ' or ' white alkali ' is dissolved in nearly boiling 
 water kept heated by steam in iron pans, until specific 
 gravity = 1-225, enough being dissolved in one operation 
 to give two, three, or four tons of crystals. The solution 
 is then filtered through bags of unbleached calico, or 
 allowed to settle for about 12 hours, then concentrated 
 in boilers over free fires until specific gravity =1 '30; it is 
 then run into settlers, and a small quantity of lime or 
 bleaching powder, or both, added. Thus the liquid is 
 
 i 2 
 
116 THE ALKALI TRADE. 
 
 clarified, after which it is allowed to settle again till the 
 temperature is 92 Fahr. when it is run into crystallising 
 coolers of cast iron, the surface of the liquid being 
 covered with bars of wood or iron, to which the crystals 
 attach themselves. After five or ten days the mother- 
 liquor is run off and boiled down, giving a white alkali 
 of weak strength. The crystals are drained, dried, and 
 packed. Sometimes the product is again purified by 
 recrystallisation. 
 
 Dr. Wright, in his paper above alluded to, gives the 
 following as loss of soda during and after lixiviation of 
 black ash: Soluble alkali left in vat waste, 3' 16 per 
 cent. ; oxidation of sulphide, inappreciable ; leakage and 
 loss during white-ash process 6*56 per cent. ; total 9*72. 
 
 Bicarbonate of Soda is, as will be shown, the product 
 of the ' ammonia process,' to be described in a future 
 chapter. It is, however, also manufactured by moisten- 
 ing the crushed soda crystals (of carbonate) with water, 
 and exposing them on cloths to the depth of two or three 
 inches, in stone or wooden boxes, to a current of gaseous 
 carbonic anhydride ; the water of crystallisation is sepa- 
 rated during the process, and there is simultaneously 
 experienced a great rise of temperature. The carbonic 
 acid is generated either by the action of hydrochloric 
 acid upon limestone, or by burning coke or coal in a 
 kiln, and washing the resulting products of combustion. 
 
 Messrs. Kurtz and Co., of St. Helen's, make this 
 material largely, by packing soda crystals in what may 
 be called iron boxes, where they are exposed to a cur- 
 rent of carbonic acid gas, made by the action of hydro- 
 chloric acid upon limestone. The product of this opera- 
 tion goes to the drying house, which is packed with 
 
BICARBONATE OF SODIUM; STATISTICS. 117 
 
 shelves, and on the top ones the substance is first placed, 
 and removed gradually to the bottom shelves at such a 
 rate that when the product reaches the lowest shelves it 
 is quite dry. It is then powdered in a mill and packed. 
 It is largely used for the preparation of baking pow- 
 ders, etc. 
 
 We are enabled, through the kindness of Mr. Edmund 
 K. Muspratt and Mr. Eichard Cail, to whom we are in- 
 debted for many important statistics having reference to 
 the alkali trade, to give here some figures illustrative of 
 the growing importance of this branch of the trade. 
 
 In 1799 there were produced on the Tyne 10 tons of 
 soda crystals, which were sold at 50/. per ton. In 1809, 
 66 tons were produced, which sold at 62. to 71/. per ton. 
 In 1866 there were produced in the Tyne district 86,000 
 tons of soda crystals, selling at 5/. 10s. per ton ; 74,000 
 tons of soda ash or alkali, selling at ll/. per ton ; and 
 11,000 tons bicarbonate of sodium, selling at 18/. per 
 ton. In the same year, in the Lancashire district there 
 were produced 24,978 tons soda crystals ; 87,314 tons 
 soda ash and refined alkali ; and 6,457 tons of bicarbonate 
 of sodium. 
 
118 THE ALKALI TRADE. 
 
 CHAPTEE VIII. 
 
 MANUFACTURE OF CAUSTIC SODA. 
 
 WE have seen in chapter vii. that after the carbonate 
 of sodium contained in the vat liquors has been crystal- 
 lised out, there remains a mother-liquor known techni- 
 cally as 'red liquor.' This contains much caustic soda, 
 and the credit is generally given to Gossage for having, 
 in 1851 or 1853, suggested the manufacture of solid 
 caustic soda from these liquors by sufficient concentration. 
 Hitherto, for most purposes, these liquors were car- 
 bonated, and a further quantity of soda ash obtained 
 from them. But Deacon has recently called attention to 
 the following extract from the specification of a patent 
 granted to Mr. George Brown, of the firm of Messrs. 
 Charles Tennant and Co., of St. Eollox, and dated Feb- 
 ruary 20, 1845 : ' Eed liquor ... is brought into a 
 metal pan, and is evaporated to about the consistency of 
 tar ; the proper quantity of nitrate of soda is then added, 
 and heat applied to expel the remaining water and flux 
 the mass,' etc. This would seem to indicate that even be- 
 fore Mr. Gossage made caustic soda in this way it had been 
 made by Tennant and Co., while still less credit there- 
 fore belongs to those various other firms which have laid 
 claim to the invention. In short, it was one of those pro- 
 gressive inventions to which no one individual can lay 
 
HISTORICAL NOTES ON CAUSTIC SODA. 119 
 
 sole claim, but in which many have a share. Amongst 
 these latter, besides those enumerated, come Mr. McBryde, 
 Mr. Lee, Mr. Gamble, and Mr. Deacon. 
 
 In 1855 Stott patented a process for removing the 
 sulphides contained in vat liquors by means of the oxides 
 of iron, manganese, or zinc, and this same process has 
 been since patented many times by different persons. 
 Bakewell was the first (1857) to patent the method of 
 packing the caustic soda in sheet-iron drums, and his 
 method is still employed. Previous to this, it was usual 
 to pour it out upon iron plates, after which it was broken 
 up and packed in wooden casks. In 1858 the method of 
 causticising with lime and oxidation of the sulphides by 
 air was patented by four gentlemen named Thomas. 
 For carrying this causticising operation into effect, it is 
 necessary to dilute the liquors, and in 1859 Mr. Dale 
 resorted to the concentration of the caustic liquors in 
 the boilers used for generating steam. This method is 
 even now employed in some works, but it is not an 
 unmixed good, owing to the crusts which form and de- 
 posit in a hard state on the boilers. 
 
 Up to 1860 most of the caustic soda produced was of 
 the character known as ' cream soda,' that is, soda which 
 has been concentrated in the state of liquor until on cool- 
 ing it has set in a hard state ; the concentration is not 
 continued to fusion. But, in November 1860, Ealston 
 patented the following improvements : ' If it is desired 
 to produce a hydrate of great strength (it is done by), 
 evaporating and separating the foreign salts, but in place 
 of keeping the heat low as hitherto, the evaporation is 
 continued, and the heat raised until the iron separates 
 as oxide of iron, and until the oxide is precipitated to 
 
120 THE ALKALI TRADE. 
 
 the bottom of the vessel, the clear alkali is then sepa- 
 rated from the iron.' But how it was possible for Bal- 
 ston to patent this method does not appear clear, for 
 Deacon has pointed out that his firm made their first 
 batch of caustic soda in this way on September 17, 1857. 
 It is further known that Gamble and Son, of St. Helen's, 
 had been even before Deacon in this respect, while Mr. 
 McBryde also made caustic soda in 1859. 
 
 For some of the foregoing observations we are in- 
 debted to Mr. George E. Davis, from whose excellent 
 article on the manufacture of white caustic soda we have 
 previously quoted. Before proceeding to describe the 
 mode of manufacture as at present conducted, we give a 
 few figures illustrative of the growth of this manufacture. 
 In 1867 there were produced on the Tyne no less than 
 3,720 tons of caustic soda, while during 1866 there were 
 made in the Lancashire district 11,213 tons of caustic soda. 
 Since then the manufacture has greatly developed, so that 
 many works now turn out from 100 to 250 tons weekly. 
 
 The process itself, starts with the production of 
 black ash or ball soda which has been already de- 
 scribed. But whereas it is an object to keep down the 
 lime as low as possible when carbonate of sodium is to be 
 made, this is not so necessary in the case of caustic soda. 
 Moreover, the lime mud from the causticiser may be 
 used for mixing with the salt-cake and slack instead of 
 so much limestone. The mixing proportions may, there- 
 fore, be either as represented in the one or other column 
 following : 
 
 A B 
 
 Salt-cake . . .2-5 cwt. ,," . 2-5 cwt. 
 
 Buxton limestone . 2*75 . . 1*5 
 
 Lime mud . . . none . . 2-5 
 
 Slack 1-5 cwt. 1-5 
 
THE CAUSTICISING OPEKATION. 
 
 121 
 
 The lixiviation of the black ash has also been de- 
 scribed in the last chapter ; and, in fact, the analyses of 
 the vat liquors therein given really relate to those ob- 
 tained from black ash so made as destined to furnish 
 caustic soda. 
 
 We here give two other analyses by Mr. G. E. Davis, 
 who has expressed the results in grms. per litre : 
 
 Constituents 
 
 50 Tw. 
 At 90 Fahr. 
 
 50J Tw. 
 At 90 Fahr. 
 
 Iron sulphide 
 
 
 0-074 
 
 0-042 
 
 Sodium sulphide 
 
 
 
 
 
 
 4-485 
 
 3-822 
 
 sulphite 
 
 
 
 
 
 
 1-323 
 
 0-979 
 
 hyposulph. 
 
 to 
 
 
 
 
 
 1-580 
 
 1-774 
 
 sulphate 
 
 
 
 
 
 
 12-707 
 
 14-258 
 
 chloride 
 
 
 
 
 
 
 19-597 
 
 23-412 
 
 silicate 
 
 
 
 
 
 
 5-961 
 
 3-774 
 
 aluminate 
 
 
 
 
 
 
 3-371 
 
 4-218 
 
 , ferrocyanide 
 
 
 
 
 
 0-133 
 
 0-416 
 
 sulphocyanide 
 
 
 
 
 
 0-211 
 
 0-196 
 
 phosphate 
 
 
 
 
 
 
 traces 
 
 traces 
 
 fluoride 
 
 
 
 
 
 
 traces 
 
 traces 
 
 carbonate 
 
 
 
 
 
 
 209-500 
 
 204-326 
 
 hydrate 
 
 
 
 
 
 
 44-800 
 
 52-740 
 
 CaO, MnO and MgO 
 
 
 
 
 traces 
 
 traces 
 
 
 
 313-742 
 
 320-857 
 
 We now come to the operation of causticising, which it is 
 impossible to carry out upon strong liquors. The vat 
 liquors are therefore reduced in strength from 50 60 
 Tw. (1-27 - 1-28 sp. gr.) to 22 Tw. (sp. gr. 1-10). 
 Some manufacturers reduce them to 14 or 16 Tw., but 
 this is quite unnecessary, and adds only to the cost of pro- 
 duction, for all the water added at this stage has to be 
 again evaporated. After settling, the liquors are run 
 into the ' causticiser,' or ' operation pan,' an apparatus 
 of varying size, and, like the ' filter,' to be presently 
 
122 THE ALKALI 'TRADE. 
 
 described, often constructed out of an old boiler. When 
 specially made, the operation pan is 25 x 6 x 6 feet, and 
 is provided with a circled bottom so as to facilitate 
 agitation, and an agitator worked by a bracket engine. 
 In addition to these, there are steam-pipes for heating the 
 charge to 100 C., a valve for running off the mud, and 
 a drop syphon for decanting the clear liquor which is 
 eventually obtained. 
 
 In some works no agitator is employed, but a current 
 of air is blown in along with the steam and this acts 
 effectually as an agitating cause, while it also serves 
 the useful purpose of oxidising any sulphides that may 
 be present. In a few works, litharge (oxide of lead) is 
 added to remove the sulphides, but the advisability of its 
 use is, to say the best for it, questionable. When used, 
 there are required about fifty pounds per ton of 60 per 
 cent, caustic soda. 
 
 It may be said that twelve good balls give sufficient 
 vat liquor for one operation in the causticiser, and from 
 this quantity there should be produced nearly one ton of 
 finished caustic soda, so that salt-cake gives about 50 per 
 cent, caustic soda. 
 
 The liquor contained in the causticiser is heated to 
 boiling by means of steam, and supplied with sufficient 
 freshly-burnt lime as free as possible from alumina and 
 silica. This is generally supplied through an iron cage 
 which retains stones and big lumps ; meanwhile, the agi- 
 tation and steaming are continued and carried on until a 
 little of the filtered solution gives no effervescence on the 
 addition of dilute acid. To an experienced workman the 
 conditions of boil, colour, and time, are indications, more- 
 over, of the approach of the ' finish.' Of course, the prin- 
 
THE CAUSTICISING OPERATION. 123 
 
 cipal reaction that occurs in the caustic! ser consists in the 
 removal of the carbonic acid from the soda, thus 
 Na 2 C0 3 + CaO = Na 2 + Ca C0 3 : but other reactions also 
 occur. Thus the lime removes much of the alumina and 
 silica which previously existed in the solution as soluble 
 salts of sodium, and in an insoluble form they are carried 
 down with the carbonate of calcium, while, when air is 
 used, part of the sulphide of sodium is converted as we 
 have already stated, into sulphate. The use of bad lime 
 often produces a liquor which will not settle well, and 
 thus traces of lime are carried on further into the process 
 of caustic making, and give future trouble. Eleven to 
 sixteen cwt. of well-burnt lime are required per ton of 
 60 per cent, caustic soda, and one to one and a-half 
 hour is consumed in the cauticising operation. After 
 settling, the liquors are run off, and the operation pan is 
 charged afresh without removing the sludge until the 
 second operation is completed. The lime-mud remaining 
 after this, is washed by agitation with water, first in the 
 pan, and then finally on a ' filter.' 
 
 This filter, as above stated, is generally half of a boiler 
 which has been cut longitudinally in twain, but when 
 specially made it is about 20 feet by 10 feet by 4 feet 
 deep. The bottom is lined with bricks set on edge, 
 about 2 inches apart, a channel being preserved along the 
 central axis. These bricks are covered loosely with 8 or 
 9 inches thickness of coke or limestone, and over this 
 comes a layer of coarse sand or cinders. Finally, over 
 the whole are spread iron grids, so as to present flat sur- 
 faces from which the lime-mud when well washed and 
 drained, can be readily removed. Sometimes this filtra- 
 tion is aided by the use of a vacuum pump, and in any 
 
124 
 
 THE ALKALI TKADE. 
 
 case it should be continued, until the mud contains about 
 50 per cent water, and gives up to water about 1 per 
 cent, caustic soda. The composition of this lime-mud, 
 just as it is used in black ash making, is indicated by the 
 following analyses by Mr. G. E. Davis. 
 
 Analyses of lime-mnd 
 
 A 
 
 B 
 
 f Calcium hydrate 
 
 
 
 
 
 2-825 
 
 2-652 
 
 < Sodium . 
 
 
 
 
 
 1-906 
 
 1-663 
 
 chloride an 
 
 d sulj 
 
 hate 
 
 
 
 0-244 
 
 0-206 
 
 Calcium carbonate 
 
 
 
 
 
 40-170 
 
 42-031 
 
 hydrate 
 
 
 
 
 
 3-756 
 
 3-072 
 
 Silica 
 
 
 
 
 
 
 0-673 
 
 0-774 
 
 Alumina . 
 
 
 
 
 
 
 0-255 
 
 0-324 
 
 Iron peroxide 
 
 
 
 
 
 
 0-048 
 
 0-708 
 
 Magnesia . 
 
 
 
 
 
 
 0-086 
 
 0-095 
 
 Soda 
 
 
 
 
 
 
 1-832 
 
 1-600 
 
 Water . 
 
 
 
 
 
 
 47-986 
 
 46-577 
 
 
 99-781 
 
 99-702 
 
 The bracketed constituents represent the part soluble in 
 100 cc. water at 100 C., calculating the amounts from the 
 results obtained in experimenting upon 5 grms. Many 
 attempts have been made to reconvert this lime-mud into 
 caustic lime for use over again in the causticiser, but the 
 process is too expensive ; moreover, by using it in the 
 black ash making, most of the soda it contains is returned 
 to the process. The washings of the lime-mud are used 
 for diluting fresh quantities of vat liquor. 
 
 The causticised liquors of from 14 to 16 Tw. are 
 now ready for concentration, an operation often effected 
 in ordinary boilers until the strength reaches 30 Tw. ; 
 after this, it is not advisable to evaporate them in the 
 boilers, for not only does the sulphide of sodium act 
 injuriously on the plates, but deposits are formed which 
 
CONCENTRATION OF CAUSTIC LIQUORS. 125 
 
 it is best, or many obvious reasons, to avoid. The further 
 concentration is therefore effected in ' boat-pans,' which 
 were first introduced by Mr. Gamble. This shape admits 
 of the ready removal of the salts which are deposited in 
 the pans after a time. A number (two or more) of such 
 pans are generally worked in concert, and are heated by 
 the waste heat from the black ash furnaces, by being built 
 over the flues leading from them. 
 
 These pans are either of wrought or cast iron, and 
 are sometimes built on the tops of the furnaces them- 
 selves ; but this plan is not to be recommended, for 
 besides the great pressure thus brought to bear upon the 
 latter, leakages into the furnace may occur and lead to a 
 stoppage, not only of the pans, but also of the furnaces, 
 The pans are about 12 feet long by 8 feet wide, and at 
 the deepest part 3 feet. When about 35 to 40 Tw. 
 (cold), the liquors are run into the ' strong pans,' where 
 the evaporation is allowed to proceed until the liquors are 
 at 280 Fahr., and test when hot, about 60 Tw. Mean- 
 while, ' salts ' are deposited, consisting of carbonate, 
 sulphate, and chloride of sodium, together with some 
 caustic soda, .etc. These are fished out, and in some 
 works a small amount of soda nitre is now added to the 
 liquors, but this is better done at a later stage. 
 
 The concentration of the liquors is still further pro- 
 secuted in the strong pans which are self-fired, until they 
 indicate 70-72 Tw., if 60 per cent, caustic is desired, or 
 80-85 Tw. if 70 per cent, caustic is the product desired. 
 The fires are then withdrawn, and the liquors allowed to 
 settle ; they are afterwards baled out into the ' pots,' and 
 the deposited salts are treated along with those pre- 
 viously obtained, as hereafter to be described. 
 
126 
 
 THE ALKALI TRADE. 
 
 The ' pots,' which are of wrought or cast iron, are 
 constructed to hold 8 or 10 tons of finished caustic soda, 
 being 9 feet in diameter, 5.L feet deep, and self-fired (figs. 
 18 and 19). These pots are liable to wear out by the 
 
 FIG. 18. 
 SCCTJON THRO C.D 
 
 direct play of the fire upon them, which is sure to find 
 out the weak points, and which produces holes in specific 
 
 FIG. 19. 
 szcrtoN THRO' A. B 
 
 i FOOT 
 
 spots ; or else at times they crack. To avoid these mis- 
 fortunes, they are turned from time to time to present 
 fresh faces to the fire. The pots are set in the ground in a 
 
FINAL CONCENTRATION AND FUSION IN ' POTS.' 127 
 
 frame of brickwork ; but the particular way in which they 
 are set varies in almost every work, One manager will so 
 arrange that the fire plays round the pot in a kind of 
 worm, and eventually escapes to the flue ; whilst another 
 will split the flame by brickwork and send it round the 
 pot in two opposite directions, meeting at the other side, 
 and so on. 
 
 About five pans of liquor are required to furnish one 
 pot of caustic. Usually three pots are used in succession, 
 the first being replenished from the pans, and the second 
 from the first, and the third from the second. More salts 
 are deposited in the first pot, and these are fished out 
 and united with those obtained from the pans. Altogether, 
 about two tons of salts are produced per ten tons of 
 caustic, and these salts being used instead of sodium 
 sulphate for making fresh black ash, carry back into the 
 process about five cwt. of caustic, eighteen cwt. of car- 
 bonate of sodium, and thirteen cwt. of sulphate of sodium 
 (Mr. Morrison). The various arrangements for concen- 
 tration all incline downwards, and the transfer of liquor 
 is effected by means of bales and spouts. 
 
 At 250 Fahr. the liquor in the pot boils and froths 
 while ammonia is evolved, and salts are deposited until 
 liquor is 85 to 90 Tw., when the liquor is dark and 
 boils at 311 Fahr. (155 C.). The ammonia is pro- 
 duced a, by decomposition of the cyanogen compounds ; 
 6, by removal of oxygen from water by the sulphides, 
 while the hydrogen reduces the nitric acid to the form of 
 
 ammonia. 1 
 
 1 Hoffmann's ' Jury Report/ 1862. 
 
128 
 
 THE ALKALI TRADE. 
 
 Strength of Solutions of Caustic Soda (Dalton). 
 
 Sp. Gr. 
 
 Na 2 in 100 
 
 Sp. Gr. 
 
 Na 2 in 100. 
 
 1-56 
 
 41-2 
 
 1-32 
 
 23-0 
 
 1-50 
 
 36-8 
 
 1-29 
 
 19-0 
 
 1-47 
 
 34-0 
 
 1-23 
 
 16-0 
 
 1-44 
 
 31-0 
 
 1-18 
 
 13-0 
 
 1-40 
 
 29-0 
 
 1-12 
 
 9-0 
 
 1-36 
 
 26-0 
 
 1-06 
 
 4-7 
 
 At 400 Fahr. the liquors in the pot are darker, and 
 the vapours are irritating, while at 500 Fahr. they boil 
 gently, and presently on increased firing the boil ceases 
 and graphite separates. This separation of graphite was 
 first observed by Dr. Pauli, and proceeds from the de- 
 composition of the cyanides, nitrogen being also evolved. 
 
 The pots are now loosely covered either with sheet iron, 
 or with covers with which they are at times specially pro- 
 vided, and the fire is urged until the contents of the vessel 
 are at a dull red heat. This consumes the graphite and 
 ' clears ' the ' pot,' after which the oxidation of the sul- 
 phides is effected, either by the addition of soda nitre or 
 by a current of air. Before oxidation there is contained 
 about 1*5 to 2 per cent, sulphide, or 35 Ib. per ton, and 
 this quantity requires 29 Ib. of oxygen for conversion 
 into sulphate. This amount of oxygen is contained in 
 56 Ib. of nitre, or about 30,000 cubic feet of air. When 
 air is used, it is pumped in by means of the same engine 
 as that which supplies the current of air for the caus- 
 ticiser, and is conveyed by means of an iron pipe. 
 
 The action of soda nitre upon sulphide of sodium is 
 represented as follows : 
 
 Na 2 S + NaN0 3 + 2H 2 0=Na 2 S0 4 + NaHO + NH 3 ; 
 or at higher temperatures, 
 
 5Na 2 S + 8NaNO j + 4H 2 0= 5Na 2 S0 4 + SNaHO + 8N. 
 
OXIDATION OF SULPHIDES IN CAUSTIC SODA. 129 
 
 During the same operation the sulphide of iron becomes 
 converted into ferric oxide. 
 
 It is estimated that about half of the nitre used, is 
 returned as caustic soda, but its economical employment 
 depends upon the relative market values of caustic soda 
 and nitre. Its employment has certainly the advantage 
 of consuming only four or five hours in the operation, 
 whereas atmospheric oxidation takes a much longer time. 
 In either case the oxidation is allowed to proceed till no 
 sulphides are present, which is ascertained by pouring 
 out a little of the fused caustic on a shovel and testing 
 it with acetate of lead. 
 
 It is possible to over-oxidise a pot, that is to make 
 it ' green ' in colour. This colour is derived from the 
 manganese, which in its turn is derived from the lime. 
 The manganese, in the presence of sulphides, exists as 
 lower oxide, but under the circumstances stated, forms 
 manganate of sodium, which has a green colour. This 
 over-oxidation may be remedied by the introduction of a 
 few balefuls of fresh unoxidised liquor. 
 
 It now only remains to reduce the strength of the 
 c caustic ' in the pots to that which is desired, and this is 
 done by the addition of salt, an agent which is cheap, 
 and which by its presence does not interfere with the 
 future uses of the product. For a caustic to contain 60 
 per cent. Na 2 when packed, it must test, before ' salting,' 
 68 to 70 per cent. NagO, while, when it is desired to 
 pack 70 per cent, caustic, it should test before salting, 
 72 per cent. Na 2 0. The quantity of salt which has to 
 be added is based upon these determinations, and on its 
 introduction a loud crackling noise is produced, while a 
 fine cloud of hot spray is thrown up, which makes its 
 
130 
 
 THE ALKALI TRADE. 
 
 presence in the air felt most unmistakably by any persons 
 in its neighbourhood. 
 
 This operation concluded, the pot is again ' brought 
 up to heat,' then the fires are withdrawn, and the con- 
 tents of the vessel, after settling during eight to twelve 
 hours, are ready for packing. This last proceeding 
 is effected by baling out the fused mass into the sheet- 
 iron drums previously alluded to. This is best done in 
 instalments, with intervals between each, so as to prevent 
 the formation of the hollow core which would otherwise 
 obtain throughout the mass, by too sudden contraction 
 into the solid state. These drums of caustic soda contain 
 about five cwt. each. 
 
 The composition of 60 per cent, and 70 per cent, 
 caustic soda is as follows : 
 
 Constituents 
 
 60 per cent. Na 2 
 
 70 per cent. Na 2 
 
 Sodium hydrate 
 
 70 to 73 per cent. 
 
 82 to 89 per cent. 
 
 carbonate 
 
 1-5 to 6 
 
 2 to 5 
 
 chloride 
 
 18 to 19 
 
 3 to 7 
 
 sulphate 
 
 5-5 to 6-5 
 
 3 to 6 
 
 sulphite 
 
 traces 
 
 traces 
 
 silicate 
 
 0-2 to 0-5 
 
 0-2 to 5 
 
 aluminate 
 
 traces 
 
 traces 
 
 The whole of the contents of the ' pots ' are not, however, 
 of this nature, for, during the settling, there is deposited 
 a denser layer, containing much ferric oxide, silica, and 
 alumina. In fact, this deposit, known as ' bottoms,' 
 ranges about seven cwt. per pot of 10 tons of 60 per 
 cent, caustic. Sometimes it finds a market as 54 per 
 cent, caustic, but is generally worked up to furnish fresh 
 liquor in the causticiser, leaving, as far as it is possible, 
 the ferric oxide behind ; or it is dissolved up and mixed 
 
MANUFACTURE OF CREAM SODA. 131 
 
 with the c red liquors,' from which is made what is called 
 * cream soda.' 
 
 ' Ked liquor ' is the mother-liquor left behind, after 
 the separation by concentration, of the carbonate of 
 sodium and other salts present in vat liquor destined to 
 furnish sodic carbonate. These salts are freed from the 
 liquor by rotation in centrifugal machines which were 
 introduced into the trade by Mr. Gamble. The liquors, 
 of specific gravity 1-5, derive their red colour from the 
 presence of a soluble double sulphide of iron and sodium ; 
 they are treated as follows : Concentration is resorted to 
 until the temperature of the solutions is about 250 Fahr., 
 when it averages 70 Tw. ; they are then allowed to cool, 
 and the deposited salts fished out. The concentration is 
 then continued till the density of the Hquors is about 
 94 Tw. ; meanwhile 2 or 3 cwt. of nitre are added, after 
 which they are run off, settled, and finally transferred to 
 the pots, which are fired till the soda tests 60 per cent, 
 alkali. At this point igneous fusion has not set in, and, 
 therefore, the product contains water over that quantity 
 necessary for the soda to exist as hydrate. No ' bottoms ' 
 are obtained in this method, and the oxidation in the pots 
 is dispensed with. Mr. Morrison gives the following 
 analysis of a sample of ' cream caustic ' (60 per cent.) : 
 
 NaHO .... 70-00 
 Na 2 C0 3 . . . .5-00 
 
 NaCl .... 7-00 
 Na 2 S0 4 .... 2-00 
 Water .... 15-80 
 Insoluble 0'20 
 
 100-00 
 Finally, we should state that the salts which are 
 
 K 2 
 
132 THE ALKALI TRADE. 
 
 fished out from the various liquors during concentration, 
 are used up in black ash making, in the place of sul- 
 phate of sodium, so that most of the soda therein con- 
 tained, is returned to the process. It should be further 
 stated that the way in which the causticised liquors are 
 concentrated, differs in particulars in almost every works, 
 but the general principles observed, remain the same as 
 those we have described. In the evaporation of the 
 liquors there is experienced a considerable loss of soda, 
 amounting to, perhaps, 5 or 6 per cent., as estimated by 
 Dr. C. K. A. Wright, but to much less as estimated by 
 others. When it is considered, however, that the total 
 loss of soda in making alkali of commerce, amounts to 
 about 13 per cent., and that the whole of the sulphur 
 contained in the salt-cake employed, was, until the last 
 few years, wasted, it is not surprising that many attempts 
 have been made to obviate these evils. Some of these 
 attempts have reference to matters already described, 
 while others have aimed at superseding Leblanc's process 
 entirely. In the next chapter we shall treat of the 
 various methods of extracting from the ' tank waste ' 
 the sulphur it contains. 
 
ALKALI WASTE. 133 
 
 CHAPTEE IX. 
 
 ALKALI WASTE ; REGENERATION OF THE SULPHUR ; MANU- 
 FACTURE OF HYPOSULPHITE OF SODIUM. 
 
 ALKALI waste constitutes the residual matter remaining 
 in the vats after the carbonate of sodium and other soluble 
 matters have been for the most part extracted by means 
 of warm water. For every ton of soda ash produced, 
 there are from 1^ to 2 tons of residual waste, so that it 
 accumulates in the districts of large works at the rate of 
 500 or 600 tons per week ; and when it is considered 
 that there are consumed annually 300,000 or 400,000 
 tons of pyrites, we are enabled to get an idea of the total 
 enormous amount of waste produced. Now soda- waste 
 contains from 15 to 20 per cent, sulphur, and Mr. Goss- 
 age has shown that this quantity represents nine-ten ths % of 
 the total sulphur contained in the original pyrites, while 
 by the pyrites two-fifths of the whole cost of the raw ma- 
 terials used in soda-making are incurred. No subject has 
 presented more difficulty in treatment than that of waste, 
 so that for years it has accumulated, and has evolved 
 poisonous gases into the air, and given off offensive drain- 
 ings which have polluted many streams. Nevertheless, 
 this nuisance has not existed so long through any lack of 
 investigation ; processes upon processes have been de- 
 vised, but until quite recently none of them have been 
 
134 
 
 THE ALKALI TRADE. 
 
 attended with that success which is essential to a large 
 industry. 
 
 The composition of waste may be seen from the 
 following analyses of Muspratt and Dawson : 
 
 Constituents 
 
 Fresh waste 
 
 Six weeks old 
 
 CaC0 3 . 
 
 41-20 
 
 23-42 
 
 Mg Si0 3 
 
 3-63 
 
 1-78 
 
 Phos. Al (Fe 2 3 ) 
 
 8-91 
 
 7-40 
 
 Ca S0 4 . 
 
 2-53 
 
 4-59 
 
 Ca H 2 2 
 
 8-72 
 
 12-03 
 
 CaS 2 . 
 
 5-97 
 
 0-62 
 
 CaS . 
 
 25-79 
 
 36-70 
 
 Na 2 S , 
 
 1-44 
 
 2-87 
 
 Water . 
 
 1-73 
 
 10-59 
 
 In 1848 this material was recommended as a manure by 
 Mr. P. Ward, but, as might have been inferred from the 
 nature of the material, this application proved anything 
 but successful. Mr. Deacon, many years ago, used it for 
 making floors, but for the most part it has been used for 
 filling up pits from which clay has been removed for 
 brick-making. 
 
 It would serve but little purpose to sketch the many 
 processes that have been at various times suggested for 
 dealing with this waste chemically, so as to obtain sale- 
 able products. We shall, therefore, only allude to those 
 which have either proved in a measure successful, or 
 which serve to delineate the history of those at present in 
 work. 
 
 Mr. Gossage endeavoured to decompose the sulphides 
 contained in waste while it was yet in the vats, through 
 the agency of impure carbonic anhydride. For this pur- 
 pose coke or coal, or these together with limestone, were 
 burnt in kilns, and the resulting gases were caused to 
 
EAELY ATTEMPTS TO UTILISE 'WASTE. 135 
 
 filter through the waste, the vats containing it being pro- 
 vided with covers and suitable arrangements. Instead of 
 carbonic acid, hydrochloric acid or the acid liquors from 
 the stills could at that time be employed, and in this way 
 a current of mixed carbonic acid and sulphuretted hydro- 
 gen gases were obtained. The last portions of gas were 
 ejected by means of steam, or, as stated in a later specifi- 
 cation, steam alone could be used without either hydro- 
 chloric or carbonic acid. The resulting gases admitted 
 of treatment in several ways. 
 
 In one system, they were mixed with more carbonic 
 acid, and air or sulphurous acid, and the total mixture 
 heated to redness, giving free sulphur and water. Or the 
 sulphuretted hydrogen could be burnt into sulphurous 
 acid, to be used for making sulphuric acid. This, how- 
 ever, would not work on account of the excessive dilution 
 of the sulphurous acid with the nitrogen of the air 
 employed to burn the hydrothion, Mr. Gossage therefore 
 condensed the sulphurous acid in a tower, and so ob- 
 tained a solution, from which he expelled the sulphurous 
 acid gas by allowing it to percolate downwards through 
 another tower in which it met a current of hot air. In 
 this case some sulphuric acid formed direct, while the 
 rest of the sulphurous acid went to the chambers. Un- 
 fortunately, none of these methods worked well in 
 practice. 
 
 When that form of the process which employed the 
 acid liquors from the stills was used, the free chlorine in 
 the acid caused the separation of a certain quantity of 
 sulphur, and the excess of acid being neutralised by the 
 lime, a quantity of sulphide of manganese was likewise 
 produced in the waste. In this way the residual product 
 
136 THE ALKALI TRADE. 
 
 admitted, it was thought, of utilisation by burning in the 
 ordinary way to furnish sulphurous anhydride. 
 
 Lee proposed to burn the sulphuretted hydrogen 
 obtained from the waste as above, into sulphurous anhy- 
 dride, to be then passed through a fire of coke or coal, 
 which maintained a chamber at a red heat. This cham- 
 ber was packed with bricks, and through the interstices 
 the products of combustion escaped into other chambers. 
 Mutual decomposition of the gases occurred in the hot 
 chambers ; the sulphurous anhydride being reduced by 
 carbonic anhydride, giving sulphur and carbonic oxide, 
 which latter served to decompose a further quantity of 
 sulphurous acid, or any bisulphide of carbon or sulphu- 
 retted hydrogen that might be present. The sulphur 
 was obtained on cooling the vapours issuing at the end 
 of the hot chamber. 
 
 Other inventors treated the waste in the manner 
 already described for obtaining sulphuretted hydrogen, 
 and caused this to react with sulphurous anhydride, 
 giving water and sulphur. 
 
 M. Favre brought the hydrosulphuric acid into con- 
 tact with moist sulphurous anhydride, while Mr. Duclo 
 obtained similar results by passing sulphurous acid gas 
 into an aqueous solution of sulphuretted hydrogen. The 
 reaction which takes place under these conditions is 
 generally represented in text-books as follows 1 : 
 
 but no matter which of the above modifications of ex- 
 periment was employed, pentathionic acid (H 2 S 6 6 ) was 
 
 1 It may be here stated that a chemical equation is not by any means 
 a mathematical one, and simply expresses generally the chief reaction that 
 occurs between two or more substances, while it fails to express the secondary 
 reactions generally attendant upon the primary one. 
 
EXTRACTION OF SULPHUR FROM SODA WASTE. 137 
 
 invariably formed and in some cases one-fifth of the total 
 sulphur was lost in this way. 
 
 Mr. Weldon, after a long series of experiments, ap- 
 pears to have perfected the process just described, and so 
 avoids the formation of pentathionic acid. This he does 
 by passing sulphuretted hydrogen gas into a solution of 
 sulphurous acid. Water dissolves at 67 Fahr. thirty- 
 seven times its own volume of sulphurous anhydride, and 
 so a solution is readily to be obtained. There are con- 
 siderations, however, which render it extremely unlikely 
 that such a process can ever be employed except for 
 utilising the sulphur in alkali waste, and, perhaps, not 
 even in that case, for, as we shall presently see, other 
 processes actually in work do this equally well. 
 
 Mr. T. Spencer, in 1859 and 1860, proposed to absorb 
 the sulphuretted hydrogen by dry sesquioxide of iron, 
 and to expose the product to atmospheric oxidation, 
 reproducing the sesquioxide and giving free sulphur ; 
 these processes to be repeated until the sulphur had 
 accumulated in quantity sufficient to burn the material 
 for supplying sulphurous anhydride to the chambers. 
 This is practically the same process as Hill's, which is 
 applied to purify coal-gas and which has been already 
 described under ' Sulphuric Acid Manufacture.' 
 
 In relation to this last subject C. Mene states that at 
 the Vaise station of the Lyons gasworks the oxide of iron 
 is regenerated as follows : When ready, it is placed in 
 a tank of iron, which is filled and hermetically closed. 
 Steam is then admitted at the bottom or sides, while 
 from the top another pipe carries off the sulphuretted 
 hydrogen resulting from the action of low-pressure steam 
 upon ferrous sulphide. Actual decomposition of water 
 
138 THE ALKALI TRADE. 
 
 is said to occur, ferric oxide being regenerated, and the 
 hydrothion escaping. One fails to perceive the advantage 
 of this process, even if it worked successfully and without 
 formation of any sulphate of iron, seeing that the hydro- 
 thion is lost, whereas in Hill's process it is regained to 
 make sulphuric acid. 
 
 In 1838 Mr. Gossage demonstrated the decomposition 
 of one equivalent of sulphide of calcium by one equi- 
 valent of carbonic acid, and the same for sulphide of 
 sodium ; and at the British Association in 1861 he stated 
 his conviction that the recovery of the sulphur would be 
 effected in this way in future years, thus producing car- 
 bonate of soda and giving hydrothion to be absorbed by 
 ferric oxide for use in the manufacture of sulphuric acid. 
 Eecently Mr. Walter Weldon has taken out a patent for 
 a developed form of this process ; or it may be applied 
 to hydrothion generated from soda waste. 
 
 As a soda process, sulphide of sodium is first prepared 
 by fluxing in a close furnace a mixture of fine coal and 
 salt-cake in the proper proportions, and lixiviation of the 
 product in water. The sulphide of sodium liquor so 
 obtained is decomposed by carbonic acid, giving sodic 
 carbonate which may be crystallised out of the solution 
 and further purified by recrystallisation. Thus 
 
 Na 2 S + C0 2 + H 2 0=Na 2 C0 3 + H 2 S. 
 
 This latter gas passes on to a series of iron vessels 
 containing water or an alkaline solution holding in sus- 
 pension hydrated peroxide of iron (as bog-iron ochre). 
 The ferric oxide absorbs the gas thus, 
 
 at the completion of the operation the ferrous sulphide 
 
WELDON'S SULPHUR RECOVERY PROCESS. 139 
 
 is oxidised by blowing air through the mixture, in this 
 way the combined sulphur is liberated : 
 
 These operations of sulphurising and oxidising are re- 
 peated again arid again till the sulphur has accumulated 
 to an extent sufficient to remove (85 sulphur to 15 oxide), 
 when the iron oxide is dissolved out by acid, leaving the 
 sulphur which is now ready to refine. If desirable,- the 
 ferric oxide can be regained from the acid solution by 
 precipitation with lime. 
 
 Now, in regard to this process, a difficulty appears to 
 exist in making sulphide of sodium from salt-cake by 
 reduction as described. In the first place, the sulphide 
 of sodium speedily destroys a furnace of the ordinary 
 kind ; secondly, it is impossible in such a furnace, to 
 prevent the oxidation of the sulphide into hyposulphite, 
 etc., while much soda appears to be lost by volatilisation. 
 The first difficulty Mr. Weldon proposes to meet by 
 using furnaces lined with carbon in the form of bricks as 
 first used by Mr. Henderson. These bricks are made by 
 mixing powdered coke with a small quantity of tar ; the 
 mixture is then moulded and exposed to a red heat. 
 
 In revolving furnaces lined with such materials it is 
 proposed first to heat powdered coke to incandescence, 
 while in another Siemens' furnace the salt-cake is heated, 
 perhaps to fusion. The reaction is to be effected in the 
 carbon-lined furnace, which will be so disposed and 
 arranged that while it admits of being heated in the 
 ordinary way, the opening at which the products of com- 
 bustion enter can also be closed at will, while the opening 
 at the other end is to be placed in communication with a 
 gas-holder. In this way Mr. Weldon hopes to surmount 
 
140 THE ALKALI TRADE. 
 
 the difficulties above enumerated. As regards the other 
 part of the process there seems to be but little difficulty, 
 except it be of that nature which necessarily attends any 
 new process. We refer, of course, to the disposal and 
 arrangement of the plant, etc. 
 
 On many series of experiments relative to these pro- 
 cesses the author was, some years ago, engaged for Mr. 
 Weldon, and he can testify to the complete success which 
 attended them in the laboratory. At the same time, 
 however, there are dangers to be apprehended, even if 
 the obstacles attending the manufacture of the sulphide 
 of sodium are overcome. Thus, during the lixiviation of 
 the furnace product, it will be a matter of difficulty to 
 avoid a very considerable oxidation ; and further, it has 
 yet, of course, to be proved that carbonic acid can be 
 obtained on a sufficiently cheap scale, in order to effect 
 that which is certainly to be desired the object of the 
 process. 
 
 In concluding our remarks on this matter, we may 
 point out that Mr. Weldon has also patented the use of 
 ferric salts in solution, for fulfilling the same purposes as 
 ferric oxide, and they also admit of regeneration by 
 oxidation. 
 
 While writing about sulphuretted hydrogen and so- 
 dium chloride, it may here be stated that the author of 
 this work has shown, in a paper read before the Chemical 
 Society, that sulphuretted hydrogen converts sodium 
 chloride into sodium sulphide at high temperatures, with 
 the evolution of hydrochloric acid ; and although the 
 percentage of salt decomposed in these experiments never 
 exceeded 15 per cent., yet, nevertheless, they were per- 
 formed under unfavourable circumstances, and therefore 
 
ACTION OF SULPHURETTED HYDKOGEN UPON SALT. 141 
 
 further experiments are well worth making, 
 which were obtained are here tabulated : 
 
 The results 
 
 Sodinm chloride used 
 in experiment 
 
 Duration of experi- 
 ment 
 
 Temperature employed 
 
 Percent, 
 of NaCl 
 decom- 
 posed 
 
 3-123 
 
 1 hour. 
 
 Sufficient to fuse salt. 
 
 6-00 
 
 3-123 
 
 1 
 
 
 
 15-00 
 
 3-123 
 
 2 
 
 Much higher. 
 
 3-38 
 
 301 
 
 10 minutes. 
 
 Below fusion. 
 
 1-10 
 
 .7215 
 
 30 
 
 
 
 94 
 
 3-0587 
 
 40 
 
 Very high. 
 
 5-51 
 
 1-0565 
 
 45 
 
 Below fusion. 
 
 1-71 
 
 844 
 
 2 hours. 
 
 Partial fusion. 
 
 2-21 
 
 2-005 
 
 1 
 
 To fusion. 
 
 93 
 
 1-4864 
 
 1 
 
 
 
 1-78 
 
 939 
 
 2 
 
 5J 
 
 8-18 
 
 1-056 
 
 3 
 
 J) 
 
 5-99 
 
 500 
 
 
 
 JJ 
 
 
 
 8-12 
 
 With the process for recovering from alkali waste the 
 mass of sulphur it contains, that we next proceed to 
 describe, the names of Guckelberger, Mond, and Schaffner 
 are associated. Guckelberger and Mond seem to have 
 worked together to a great extent, the work being con- 
 tinued afterwards by Mond alone. Schaffner's investiga- 
 tions, so far as we propose to enter into them here, have 
 to do only with the purification of the sulphur prepared 
 from the waste. 
 
 The chemical reactions involved in the process were 
 first proposed for realisation on a manufacturing scale by 
 Mr. Thomas H. Leighton in 1836, and long before Mr. 
 L. Mond introduced the process in an improved form, 
 it had actually been in use at various works in Great 
 Britain. 
 
 Where the process is employed, in addition to the 
 four tanks or vats usually employed in a series, for lixi- 
 viation of black ash, six others are used. Three of these 
 
142 THE ALKALI TRADE. 
 
 always contain black ash in course of lixiviation, while 
 one is either casting or filling, and the other six are full 
 of waste in the different stages of the process under de- 
 scription. 
 
 The waste left in the tanks is submitted to a current 
 of air which is forced under through false bottoms with 
 which the tanks are provided, during fourteen or eighteen 
 hours. The current of air is obtained by means of a fan 
 of Schieles' construction, of 20 inches diameter, such a fan 
 being sufficient for the treatment of the waste obtained 
 in converting 100 tons of salt-cake per week. During 
 this oxidation process, the temperature rises to about 200 
 or 230 Fahr., and when it has progressed so far as 
 stated, weak liquors from former lixiviations are poured 
 on to the waste and drained through ; the washing being 
 repeated until the liquors are about 10 or 12 B. This 
 operation takes from 8 to 10 hours to complete, and 
 these processes of oxidation and lixiviation are repeated 
 in all, three times. 
 
 The composition of the liquors so obtained, depends 
 upon the quality and the degree of humidity of the waste, 
 the time taken in oxidation, and the temperature. The 
 amount of sodium compounds in soda waste is equal in 
 terms to 4 or 5 per cent. Na 2 S0 4 on the average, while the 
 following analysis by C. Stahlschmidt fairly represents 
 the constitution of the liquors taking 25 cc. : 
 
 CaS 5 = 0-309 gramme. 
 
 4CaO,CaS 4 + 18'Aq . . =1-106 
 
 CaS0 4 = 0-033 
 
 CaS0 3 . = 0-275 
 
 Na 2 S 2 3 . . . . = 0-845 
 
 CaH 2 S 2 = 0-070 
 
 NaHS = 0-386 
 
MOND'S SULPHUR RECOVERY PROCESS. 143 
 
 For good working results, the liquors should contain 
 at least one equivalent of CaS 2 3 for every two of CaS 2 , 
 and one of CaS 2 3 for every one of CaH 2 S 2 (according to 
 Mond). Practically they may be said to consist of hypo- 
 sulphites and sulphides, and it is an object to obtain 
 these constituents in such relative proportions as may be 
 required on treatment with acid to yield sulphuretted 
 hydrogen and sulphurous acid in the quantities necessary 
 to produce only sulphur and water. 
 
 The liquors are allowed to settle in tanks, and are 
 then run into a wooden vessel lined with lead, of 10 to 
 12 feet diameter, and 3 to 6 feet in height, and main- 
 tained at a temperature of 140 to 150 Fahr. by steam. 
 Hydrochloric acid of 20 B. is now added, then more 
 sulphur liquor, then more acid, and so forth alternately, 
 in the proportion of 8 : 1 or 7 : 1. Meanwhile the tem- 
 perature is maintained (60 C.), and the liquors are kept 
 in agitation until the vessel is sufficiently fall, when acid 
 is finally added until an odour of sulphurous anhydride 
 is perceptible. Into other tanks the liquors after being 
 so treated are then run, and here the sulphur speedily 
 settles, and is then washed by a stream of water. Finally, 
 it is raked out into drainers below, constructed of bricks 
 and tiles, which are heated underneath. The resulting 
 product contains 60 per cent, water, and it then only 
 remains to be melted and refined in an apparatus which 
 has been improved by Schaffner. 
 
 Through the kindness of Messrs. Daglish and Co. we 
 are enabled to reproduce here a sketch (fig. 20) of a 
 steam sulphur melter as commonly employed. In such 
 an apparatus the sulphur is exposed to steam at a pres- 
 
144 
 
 THE ALKALI TRADE. 
 
 FIG. 20. 
 
 sure of 20 Ib. to the inch, when it melts and sets free the 
 water, which floats on the top of the molten sulphur. 
 Sulphate of calcium and other impurities subside to the 
 bottom, and the fluid sulphur is blown off by the steam 
 into moulds or tubs. If the hydrochloric acid used 
 in its manufacture be free from arsenic, so also will 
 be the sulphur, which is useful not only for the manu- 
 facture of pure sulphuric acid, but 
 also in the preparation of gunpowder, 
 for which purpose it is most largely 
 used. The amount of sulphur so re- 
 covered varies, but Mr. Mond states 
 that he has obtained as much as 60 
 per cent, of the total amount contained 
 in waste ; practically, however, not 
 more, we believe, than two-fifths are 
 recovered. 
 
 M. Schaffner shows that alkali 
 waste after this treatment consists 
 principally of carbonate and sulphate 
 of calcium, together with some calcic 
 sulphite. He further credits it with the 
 power of preserving railway sleepers, 
 while it is also stated to be of use as 
 a manure and for building purposes. 
 Notwithstanding the merits of the process we have 
 described, it has proved remunerative in the hands of but 
 few manufacturers, and is not largely used on account of 
 the small profit realised by its working. 
 
 The sulphur recovery process worked on the largest 
 scale in this country is Mactear's. The process is in 
 work at St. Eollox, Glasgow, where I am informed by 
 
MACTEAE'S SULPHITE-RECOVERY PEOCESS. 145 
 
 Mr. James Mactear that about 30 tons of sulphur per week 
 are made by his process, and more could be made were 
 it required. This process has two modifications. In 
 the one, the yellow liquors obtained by collecting the 
 drainage from the waste, or by oxidising and lixiviating 
 the waste, are mixed with lime in a finely divided and 
 hydrated state, and submitted to the action of sulphurous 
 acid in a wooden vat fitted with an agitator. The sul- 
 phurous acid is absorbed, and seeing the yellow liquors 
 consist chiefly of calcium sulphides, some sulphur is de- 
 posited. At the same time that sulphur is precipitated, 
 calcium hyposulphite forms, and some hydrothion is 
 evolved. The liquor is now mixed with fresh yellow 
 liquor in suitable proportions, preferably so as to contain 
 an equivalent of calcic hyposulphite to each two equiva- 
 lents of calcic bisulphide, and one of hyposulphite 
 (CaS 2 3 ) to one of sulph-hydrate of calcium (CaSHS). 
 The hydrothion evolved is passed into liquor which has 
 been previously treated with sulphurous acid, so that it 
 is thereby decomposed, with precipitation of sulphur. 
 Or it may be passed into milk of lime, and the product 
 added to fresh yellow liquors requiring treatment. The 
 liquors treated as above set forth are now decomposed 
 with hydrochloric acid in suitable wooden vessels, thus 
 giving a solution of calcic chloride (CaCl 2 ) and sulphur, 
 which latter is collected and dried, or melted for use 
 or sale. 
 
 The other modification, being the one which is ac- 
 tually used at St. Eollox, is as follows : The yellow 
 liquors, without being treated with lime, are placed in a 
 wooden vat provided with an agitator, and kept stirred 
 while a solution of sulphurous acid is run in. Prac- 
 
 L 
 
146 THE ALKALI TRADE. 
 
 tically hydrochloric acid is added to the yellow liquor, 
 sulphurous acid being run in along with the other two 
 streams, keeping the temperature at about 145 Fahr., 
 and proportioning the streams as to yield chloride of 
 calcium and sulphur, which is collected, washed, and 
 dried as before described. 
 
 It is of some interest to note that when alloxan (an 
 oxidation product of uric acid) is treated with sulphur- 
 etted hydrogen, alloxanthine is formed, and sulphur set 
 free, thus 
 
 Could the alloxan be regenerated from the alloxan- 
 thine, a process might be worked out for the recovery of 
 sulphur in this way. Now, it is well known that allox- 
 anthine may be reconverted into alloxan by moistening 
 it with a mixture of 2 parts fuming nitric acid (1'52 
 sp. gr.) with one part of ordinary nitric acid (1*42 sp. gr.), 
 when nitrous acid is copiously evolved, and after some 
 time the reaction is complete. 
 
 Here, therefore, we have chemical grounds for a pro- 
 cess to recover the sulphur from waste, and without any 
 loss of nitric acid, for the nitrous acid evolved could be 
 again converted into nitric acid for further use. The 
 alloxan could be made from guano. 
 
 It is worthy of record that among other unsuccessful 
 undertakings for the regeneration of sulphur from waste, 
 is one which originated with Mr. I. Lowthian Bell. He 
 proposed to make factitious pyrites (so called) by heating 
 in a blast-furnace a mixture of soda waste and the residue 
 left by burning pyrites. So far as the mere union of the 
 sulphur and the iron was concerned, the undertaking was 
 
MANUFACTUKE OF SODIC HYPOSULPHITE. 147 
 
 eminently successful, and, in fact, some 2,000 to 3,000 tons 
 of the factitious pyrites were actually made. But, beyond 
 certain destructive influences on the furnaces, the cost 
 was too great at the time to warrant continuation of the 
 manufacture ; not only so, but the difficulty was in- 
 creased by the discovery that the product could only be 
 burnt so as to regain the sulphur for chamber consump- 
 tion, when in union with coal-brasses or native pyrites. 
 Nevertheless, Mr. Bell has pointed out that should native 
 pyrites experience an improvement in price, or coal a 
 great deterioration, the process might, after all, be em- 
 ployed more or less widely. The least that can be said 
 of the process is, that it was as ingenious as the under- 
 taking was commendable. 
 
 While treating of alkali waste we may conveniently 
 refer to the manufacture of hyposulphite of sodium, 
 although this substance is not largely produced. Its pro- 
 duction in Great Britain is, we believe, confined to the 
 Tyne district, and at Walker the process which is fol- 
 lowed, is somewhat as now to be stated. 
 
 Tank or vat waste is exposed to the atmosphere, 
 whereby the sulphides of calcium are converted into 
 hyposulphite. The product is made into a thin paste or 
 solution with water, and is then heated with sulphate 
 or carbonate of sodium. In this way sulphate or car- 
 bonate of calcium is precipitated, while sodic hyposulphite 
 remains in the solution, and is obtained therefrom on 
 concentration and crystallisation. 
 
 In 1863 about five tons were made weekly by this 
 method at Walker- on-Tyne. Another process, used at 
 Newcastle, consists in the reduction of sulphate of sodium 
 
 L 2 
 
148 THE ALKALI TRADE. 
 
 to sulphide by means of coal, in a close furnace. The 
 ' balls ' which result from this operation are extracted 
 with water, and the solution after settling, is exposed to a 
 current of sulphurous anhydride. It is then concentrated 
 in the open air, and on cooling the sodic hyposulphite 
 crystallises out. 
 
OTHER SODA-MAKING PROCESSES. 149 
 
 CHAPTER X. 
 
 SODA PROCESSES OTHER THAN LEBLANC'S, INCLUDING THE 
 'AMMONIA PROCESS.' 
 
 UNDER this heading it is our intention to briefly indicate, 
 and in some measure describe, processes which have been 
 proposed from time to time, either as supplementary to, 
 or substitutive of, the one in general use. Most of them 
 are improved modifications of old processes, and have 
 been tried on a limited scale, while others are actually in 
 use to a small extent. 
 
 Some years ago Mr. Hunt proposed a process, founded 
 on some experiments of Mr. Gossage, and which, indeed, 
 was an old friend in a new garb. It was proposed to 
 obtain crude sulphide of sodium by fluxing salt-cake 
 with coke or coal ; the product was to be broken into 
 lumps and placed in iron cisterns provided with false 
 bottoms, under which carbonic anhydride was forced, the 
 gases passing out at the top. Each vessel was to be 
 heated by steam, and the carbonate of sodium so obtained 
 to be purified by recrystallisation. As for the sulphur- 
 etted hydrogen evolved in the reaction, this was mixed 
 with air and burnt under a stratum of oxide of iron kept 
 red-hot by the burning gases, and in this way sulphurous 
 anhydride was produced for use in the chambers. The 
 chief difficulties encountered in the working of such a 
 process are those which Mr. Weldon hopes to avoid, 
 
150 THE ALKALI TRADE. 
 
 and as we have already described his process and its 
 advantages in our last chapter, we may pass from its 
 consideration. 
 
 Mr. Arrot, Mr. Hunt, and others have also proposed 
 at various times to manufacture caustic soda from the 
 sulphide made as above, by the use of oxides, such, for 
 instance, as those of iron, manganese, zinc, and copper. 
 Where iron is used, a double compound of sulphide of 
 iron and sodium results, which is difficult to manipulate. 
 But in any case a greater difficulty so far, consists in the 
 manufacture of the sodic sulphide. This has been at- 
 tempted by causing a fused stream of sulphate of sodium 
 to flow through red-hot coke or coal, but with partial 
 success. If by Weldon's plan, good results should be 
 obtained, then these various other processes would merit 
 reconsideration. 
 
 The processes we shall next describe, refer to the 
 extraction of soda contained in felspar, cryolite, and other 
 minerals. 
 
 Ward proposed to frit any natural silicate, as pumice- 
 stone, with calcium fluoride and chalk, in a reverberatory 
 furnace, by which operation, supplemented by lixiviation 
 of the product, a solution of caustic soda is obtained ; the 
 residuum he employed as a hydraulic cement. 
 
 Newton patented the use of the following propor- 
 tions : 100 parts felspar, 50 parts phosphate of lime, and 
 300 to 400 parts of lime, all in powder. This mixture 
 was calcined at a low red heat for two hours, by which 
 means there are formed silicate of lime and phosphate of 
 sodium ; the silicate of lime combines with the silicate 
 of alumina, and on lixiviation, the lime decomposes the 
 phosphate of sodium, reproducing phosphate of lime and 
 
SODA FROM CRYOLITE. 151 
 
 giving caustic soda, which remains in solution. The 
 residue obtained in these operations was recommended 
 as a manure. 
 
 The attempts to obtain soda from cryolite, which 
 is a double fluoride of sodium and aluminium, origi- 
 nated with Spilsbury, and were revived by Moigno. 
 But it is by a process devised by Julius Thomsen in 
 1850, that such an amount of soda is actually manu- 
 factured at the present day, as to consume annually 
 12,000 to 15,000 tons of cryolite. Cryolite occurs almost 
 exclusively in South Greenland, where it forms a solid 
 mass of about 600 feet in length and 200 feet in width, 
 and of unknown depth. This mine is the property of the 
 Danish Government. 
 
 The following description of the manufacture of soda 
 from this mineral is taken from a paper by J. Lawrence 
 Smith. The decomposing agent employed is lime, and 
 the process can be performed either in the wet or dry. 
 
 The Dry Process. The cryolite, crushed to powder, 
 is mixed with slaked lime or powdered chalk in such pro- 
 portions that for each equivalent of pure cryolite there 
 shall be rather more than six equivalents of lime. In 
 the next process of calcination, the great difficulty of the 
 process is encountered. The heat must only be great 
 enough to effect the decomposition, for if the temperature 
 exceeds this, the materials fuse, and produce a product it 
 is impossible to lixiviate. About two hours are required 
 to complete the decomposition of a charge of 1,000 lb., 
 and the product, when properly made, is a granular loose 
 mass of an ash colour. After cooling, it is lixiviated by 
 water, and yields a solution of soda and sodium alumi- 
 niate, which marks on an average 26 to 28 Baume". The 
 
152 THE ALKALI TRADE. 
 
 liquors are placed in large horizontal cylinders, provided 
 with agitators, where the solution is treated with carbonic 
 acid, produced by the combustion of coke and washed 
 with water, by being made to traverse stacks of faggots 
 over which water trickles. The carbonic acid converts 
 the caustic soda and aluminate into carbonate, setting 
 free the alumina, thus 
 
 2 (Na 3 A10 3 ) + 3C0 2 - 3Na 2 CO 3 + A1 2 3 . 
 
 The liquors now mark about 31 Baume, and furnish 
 soda, while the alumina is allowed to settle, and in this 
 state of granular powder constitutes a valuable source of 
 alums. The carbonate of soda obtained is tolerably pure, 
 containing only 1 or 2 per cent, of sulphate of sodium, 
 derived from the sulphides associated with the cryolite. 
 
 The Wet Process differs from the dry, according as the 
 required product be carbonate, or caustic soda. If car- 
 bonate be desired, the proportions above stated are used ; 
 but when caustic is the desideratum, fifteen equivalents of 
 lime are employed to two of cryolite, the resulting pro- 
 ducts being caustic soda, aluminate of lime, and fluoride 
 of calcium, which last-named body is formed in either 
 case. The operation is conducted in a large vertical 
 cylinder heated by steam and provided with an agitator, 
 and takes from two to three hours' boiling. The liquors 
 are filtered and settled, and are treated with carbonic 
 acid as above (with the same result) if carbonate of soda 
 be desired. On the other hand, when caustic soda is 
 required, the liquors are simply evaporated in the usual 
 way, yielding caustic soda of 75 per cent. 
 
 The wet process has many advantages over the dry 
 method, but inasmuch as lyes of only 10 Baume are so 
 
SODA FROM CRYOLITE. 153 
 
 produced, there is an enormous consumption of fuel 
 necessitated by evaporation. 1 
 
 There are four establishments in Germany consuming 
 about 2,000 tons of cryolite annually, and in 1867 one 
 was started in Pennsylvania for working 6,000 tons. At 
 this works, in Natrona, caustic soda is made as above 
 on a large scale. Bauxite (a mineral containing 80 per 
 cent, of alumina) is sometimes mixed with the cryolite to 
 increase the yield of alumina. 
 
 The following equations, although they may not re- 
 present exactly what occurs in the two forms of the pro- 
 cess described, nevertheless do so fairly : 
 
 1st. Dry Process 
 
 2(3NaF,AlF 3 ) + 6CaO=2Na 3 A10 3 + 6CaF 2 . 
 
 Any caustic soda present in the product would seem 
 to result only from the presence of water in the lime 
 used, thus 
 
 2 (Na 3 A10 3 ) + 3CaH 2 2 =61SraHO + 3CaO + A1 2 3 . 
 2nd. Wet Process 
 2(3NaF,AlF 3 ) + 6CaH 2 2 =6NaHO + 6CaF 2 + A1 2 3 3H 2 0. 
 
 The various products manufactured from cryolite 
 have a market value of more than $1,500,000 in gold. 
 
 Allied to the processes just described are others in 
 which salt is decomposed by silica and steam. Blanc 
 and Blazille (1840) used a mixture of 280 parts of salt 
 and 200 of sand, which was enclosed in red-hot iron 
 cylinders, and exposed to a current of steam. In this 
 
 1 It is not easy to see why four or five such cylinders should not be 
 worked in a series, like as vats are worked in Lancashire. In this way the 
 liquor from the first operation would be used in the second, and so on, and 
 thus stronger liquors would be obtained. 
 
154 THE ALKALI TKADE. 
 
 way hydrochloric acid is evolved, and neutral sodic sili- 
 cate produced. This latter was then fluxed with sodic 
 carbonate, and the product dissolved in water, then 
 treated with carbonic anhydride, thus obtaining the 
 whole of the alkali as carbonate, and the silica in a 
 finely-divided precipitated state, fit for use over again, or 
 for glass-making. The evil of the process consists in the 
 difficulty experienced in obtaining anything like a perfect 
 decomposition of the salt, and the gelatinous nature of 
 the precipitated silica, 
 
 Tilghmann (1847) and Fritzsche (1858) obtained 
 neutral silicate of sodium in the same way, but treated it 
 by lixiviation with water, and decomposition of the solu- 
 tion by caustic lime ; but the silicate of lime so produced 
 was so bulky, and had such a retentive nature for the 
 caustic fluid, that the process did not succeed in practice. 
 Tilghmann also attempted to decompose sulphate of so- 
 dium in the presence of alumina by hot steam, thus form- 
 ing sulphuric acid, which was carried away by the steam, 
 and aluminate of sodium, which was decomposed in 
 water by carbonic acid, giving sodic carbonate, and re- 
 generating the alumina. But the form of process with 
 which the name of Tilghmann is most intimately asso- 
 ciated employs common salt, alumina, and steam, in which 
 case the following equations represent the reactions on 
 which the process is based : 
 
 (1) Al 2 3 + 6NaCl + 3H 2 0=2Na 3 A10 3 + 6HCl. 
 
 (2) 2Na 3 A10 3 + 3C0 2 =3Na 2 C0 3 + Al 2 3 . 
 
 This beautiful process excited much attention some 
 years since, but, in many experiments conducted at 
 Glasgow, alkali of low strength only could be produced. 
 
 An interesting process was patented in Prussia, in 
 
LUNGE'S SODA PROCESS. 155 
 
 1867, for obtaining caustic soda and nitric acid from 
 Chili saltpetre (NaN0 3 ). Equivalent quantities of this 
 substance and chalk are heated in iron vessels, and the 
 evolved gases conducted into water, giving, it is said, 
 eleven- twelfths of the original nitric acid. The mass left 
 in the retorts consists of lime and sodic carbonate ; and 
 this, on treatment with water, gives caustic soda, and 
 regenerates the carbonate of calcium. This process might, 
 perhaps, be worked with advantage in Chili and Peru, 
 where soda nitre abounds ; but here, the nitre is far too 
 costly (for reasons previously given) to admit of the use 
 of such a process. As regards the process itself, there 
 appears to be a rapid destructive action on the iron pots ; 
 but it is not at all improbable that muffle furnaces could 
 be used instead. 
 
 Sheridan, in 1837, proposed to decompose salt direct 
 by highly heated steam ; and in 1862, E. W. Swinbourne 
 proposed to use superheated steam and fused salt. This 
 is a very favourite idea with chemists ; but to those who 
 have repeated these observations it is well known that it is 
 impracticable to get a perfect decomposition, and, more- 
 over, the salt is volatile at a strong red heat. What 
 reaction takes place, occurs but slowly, and very dilute 
 hydrochloric acid is therefore obtained. 
 
 Patents for the decomposition of salt by means of 
 electricity have also been secured by Cook in 1851, Watts 
 in 1851, and Stanley in 1853. 
 
 We will now pass on to regard a new process pro- 
 posed by Dr. Lunge, and described before the Newcastle- 
 on-Tyne Chemical Society as follows : ' Carbonic acid, 
 made as rich and as pure as possible, is forced through a 
 series of closed vessels, the first few, or " converters," 
 
156 THE ALKALI TRADE. 
 
 containing a solution of sodium sulphate and barium 
 carbonate ; the next, which I will call " precipitators," 
 standing at a higher elevation, and containing solution of 
 barium sulphide, the escaping impure sulphuretted hy- 
 drogen being dealt with in any of the manners previously 
 defined. The operation produces in the " converters " 
 a precipitate of barium sulphate (which is afterwards 
 reduced to sulphide and charged into the " precipitators ") 
 and a solution of sodium bicarbonate (which is boiled 
 down and dried, yielding solid alkali and gaseous car- 
 bonic acid). The same operation produces in the pre- 
 cipitators, by the action of the residual carbonic acid, the 
 conversion of barium sulphide into carbonate, which is 
 run in the state of mud into the converters, and serves 
 for a fresh operation there/ etc. 
 
 This process is based on the fact, discovered by Wag- 
 ner, that bicarbonate of barium acts far more effectually 
 in decomposing sulphate of sodium than the normal car- 
 bonate. M. Kuhlmann, however, found the operation 
 impracticable on a large scale, but obtained better results 
 by working under a pressure of four or five atmospheres. 
 But such a pressure is awkward and costly to secure. 
 The advantage thus presented, however, is due to the 
 increased solubility of barium bicarbonate. 
 
 One advantage presented by Dr. Lunge's process 
 is that pure carbonate of soda is obtained, and the 
 theoretical quantity of artificially-prepared barium car- 
 bonate suffices; but if native witherite be used, four 
 times this quantity is required. On a scale of several 
 hundredweights, Dr. Lunge always found he could obtain 
 a perfect conversion of the sulphate in three or four 
 hours, even at ordinary atmospheric pressure ; but in 
 
LUNGE'S SODA PEOCESS. 157 
 
 working on a manufacturing scale by his apparatus, 
 there would be a pressure of 15 Ib. to the square inch 
 in the first converter. As much as 99.=> per cent, of the 
 calculated sodium carbonate obtainable was realised in 
 Dr. Lunge's experiments, and if this could be realised on 
 a large scale, it would certainly compare very favourably 
 with Leblarfc's process, in which there is a loss of 12 to 
 15 per cent, on the theoretical quantity. 
 
 Ozouf s plan of obtaining pure carbonic acid would 
 be useful here, if practicable. It consists in passing any 
 impure carbonic acid through a solution of sodium car- 
 bonate, which retains the carbonic acid whilst foreign 
 gases escape. The carbonic acid so absorbed is again 
 expelled by heat. But Dr. Lunge considers the carbonic 
 acid obtained by burning coke in a lime-kiln to be quite 
 good enough, if it be cooled and washed. The greatest 
 difficulty experienced in the process would be in dealing 
 with the sulphuretted hydrogen. 
 
 The first start would be made with native heavy 
 spar, and Dr. Lunge has convinced himself that 90 per 
 cent, of the barium sulphate can be reduced by coal-dust 
 in a good reverberatory furnace, contact with air being 
 as much as possible avoided. On an average he obtained 
 a reduction of 80 per cent., and that which escapes re- 
 duction is again obtained on lixiviation. In fact, the 
 reduction of barium sulphate is effectually performed at 
 one or two works on the Continent on a large scale. 
 
 Dr. Lunge concludes his paper in these words : ' I 
 would not like to say that my process allows a given 
 quantity of sulphate to be worked up as cheaply as 
 Leblanc's process, for the reduction of barium sulphate 
 will cost about as much labour and coals as the " ball- 
 
158 THE ALKALI TRADE. 
 
 ing " process.' There is also the cost of producing car- 
 bonic acid, and, in the present state of affairs, the loss of 
 sulphur; but against this, the process does not present 
 a loss of 12 to 15 per cent, alkali, and the product is 
 free from sulphate, sulphite, and hyposulphite. 
 
 We have dwelt somewhat at length with these notes 
 from Dr. Lunge's paper, because they contain* many valu- 
 able hints, even if the process should never have an 
 existence on an extended scale. 
 
 We might extend our considerations upon suggested 
 processes for making soda yet very much ; but as our 
 object is not to exhaust the subject, but only to indicate 
 the most reasonable ones, or those which are, or have 
 been, actually in work, we shall only pause to notice 
 two others. 
 
 The first of these is known as Bachet's process for 
 making caustic soda, and may be said to constitute an 
 improved form of the process originally employed by 
 Lord Dundonald and Mr. Losh, at the end of the last 
 century (1790-1799). This consisted in the decomposi- 
 tion of salt by means of litharge ; but, as the process was 
 then worked, less than 6 per cent, of the salt used was 
 decomposed, and great loss of lead was experienced. 
 Nevertheless, at that date caustic soda was thus made at 
 a profit ; and this need not surprise us, for Mr. E. Cal- 
 vert Clapham has calculated that this product was then 
 worth from Sbl. to 90/. per ton of 70 per cent. In 
 M, Bachet's process hydrate of lime is used in addition 
 to salt and litharge, and with such a mixture many ex- 
 periments were made at Walker (1869 and 1870), and 
 have been described by Mr. Clapham. 
 
 The best results were obtained, using a mixture of 
 
BACKET'S CAUSTIC SODA PROCESS. 159 
 
 100 parts litharge, 70 parts salt, and 50 of lime. This 
 mixture is ground on a mill with some water, so as to 
 form a paste, and the reaction takes place at this stage, 
 19 or 20 per cent, of the salt being decomposed, forming 
 chloride of lead, and giving caustic soda. Preferably, 
 this liquor, which is obtained from the pulpy mass by 
 pressure in a mill worked at a pressure of 145 Ib. to the 
 square inch, is used over again for treatment of fresh 
 quantities of the original mixture, and so in this way 47 
 or 50 per cent, of the salt admits of decomposition. 
 
 Now this solution contains lead which has to be 
 removed, and this is best done by filtration through 
 hydrate of lime which can afterwards be used in the 
 process. From the liquors thus freed from lead, caustic 
 soda of 70 per cent, can be obtained in the ordinary way, 
 if care be taken to fish out the common salt deposited on 
 concentration. The cakes left in the press are dried at 
 a temperature of 350 Fahr., by which operation the 
 hydrate of lead is converted into yellow oxide, but higher 
 oxides appear to form also, and these suffice, as is sug- 
 gested by Mr. Clapham, to explain why this material 
 does not act so well after it has been regenerated several 
 times. The mass so dried, is thrown into boiling lime- 
 water to decompose the chloride of lead, after which, 
 and draining, it is ready for use over again in decom- 
 posing fresh quantities of salt. Although many difficul- 
 ties were experienced in working this process, yet Mr. 
 Clapham held out hopes that it would prove to make 
 caustic at a cheaper rate than the one in almost universal 
 use. Unfortunately, since the date of his paper, but little 
 has been heard of the further history of the undertaking. 
 
 More than 20,000 tons of caustic soda are made 
 
160 THE ALKALI TRADE. 
 
 annually in England, of the value of 350,000/., and, 
 therefore, any question regarding an improvement in such 
 a trade deserves the most careful study. 
 
 The only remaining plan of making soda that calls for 
 study here, is technically known as the ' ammonia pro- 
 cess,' and it is the only one which, as a rival to Leblanc's, 
 has met with any measure of success. The following list 
 of patents having reference to it, shows how great is the 
 interest taken in it : Dyer and Hemming (its inventors), 
 in 1838 ; Schlcesing, in 1854 ; Gossage, in 1854 ; Belford, 
 in 1855 ; Schlcesing and Eolland, in 1858 ; Solvay, in 
 1863 ; Solvay in 1867 ; Young, in 1871 and 1872 ; 
 Solvay, in 1872 ; Weldon, in 1872 and 1873. 
 
 The process itself consists in treating a solution of salt 
 with bicarbonate of ammonium, practically with carbonic 
 acid gas and ammonia at the same time, to saturation. 
 Bicarbonate of sodium is thus produced, and a solution of 
 ammonic chloride results, from which the ammonia is 
 regenerated. The process may be said to depend upon 
 the relative solubility of chloride of ammonium and 
 sodium bicarbonate, and therefore it is necessary to work 
 with very strong solutions. Gossage prepared his bicar- 
 bonate of ammonium by exposing currents of carbonic 
 anhydride and ammoniacal gas to a shower of water in a 
 tower, and decomposed common salt either with the dry 
 product, or direct by ammonia and carbonic anhydride. 
 From the sodic bicarbonate so produced, the second mole- 
 cule of carbonic anhydride was recovered by heating the 
 substance in iron retorts. But he found the great dif- 
 ficulty of the process to exist in the loss of ammonia. 
 
 It has been stated that the following reaction cannot 
 be realised in practice : 
 
 NaCl + NH 3 + C0 2 + H 2 0=NaHC0 8 
 
THE 'AMMONIA PROCESS.' 161 
 
 for with equivalent quantities of ammonia and salt, even 
 when excess of carbonic anhydride is used, only two- 
 thirds of the soda are obtained as bicarbonate, and thus 
 a large amount of bicarbonate of ammonium is wasted. 
 If two equivalents of salt be taken to one of ammonia, 
 four-fifths of the ammonia are utilised, but much salt 
 remains undecornposed. Moreover, carbonic anhydride 
 must be employed in a pure state and under considerable 
 pressure in order to insure perfect absorption. 
 
 These, however, constituted the objections (among 
 others) to the process many years ago, while, as a matter 
 of fact, many improvements have really been introduced, 
 and, indeed, the process is in work at Couillet, Aix-la- 
 Chapelle, Kasan, Northwich, and other places. The par- 
 ticular improvements effected by Honigmann, of Aachen, 
 and Gerstenhofer, of Freiberg, are kept secret, as are also 
 some of the most important (according to statement) of 
 Solvay's improvements. It is certain that some time ago 
 25,000 to 50,000 Ib. of sodium carbonate were being 
 made daily at Couillet, but there is much difficulty in 
 ascertaining, even- now, whether at that place, or any- 
 where else, it is fulfilling the expectations anticipated of 
 the process. 
 
 According to one account, the process is conducted 
 as follows : A saturated solution of salt is made in 
 vessels arranged on the same principles as lixiviating vats, 
 and the solution of 23 or 24 is transferred to a vessel 
 provided with a false bottom pierced with holes, wherein 
 it is saturated with ammonia. Great heat is evolved, and 
 the volume of liquid is sensibly augmented, so that it 
 registers only 16 after this treatment. The solution is 
 then cooled down by means of a worm of cold water, and 
 
 M 
 
162 
 
 THE ALKALI TEADE. 
 
 is then ready for treatment with carbonic anhydride. This 
 is obtained either by roasting limestone, or treating it with 
 acid, and passes, after washing in water, into the aforesaid 
 solution which is contained in cylindrical vessels, or ab- 
 sorbers, 30 to 40 feet high, and with nearly a like diameter. 
 The gas enters from below, under a pressure of 1*5 to 2 
 atmospheres, and by having to rise through the liquid, the 
 temperature is kept within the desired limits. The liquid, 
 saturated with carbonic anhydride, is drawn off every half 
 hour, and the resulting bicarbonate of sodium is collected 
 on a filter, washed with a little water, and is made then 
 to pass down a tower, in which it meets hot gas or ascend- 
 ing steam. Passing alternately by a spiral arrangement 
 from the centre to the circumference, and vice versa, it 
 reaches the bottom as ordinary carbonate, ready for sale. 
 The carbonic anhydride evolved in this last operation is 
 conveyed to the absorbers. 
 
 According to Honigmann, in order to produce 
 10,000 Ib. of carbonate of sodium, there are required 
 
 Substances consumed 
 
 1. 90 per cent. 
 
 2. 95 per cent. 
 
 3. 98 per cent. 
 
 
 Ib. 
 
 Ib. 
 
 Ib. 
 
 Common salt 
 
 20,000 
 
 19,000 
 
 17,500 
 
 Coal 
 
 20,000 
 
 15,600 
 
 15,000 
 
 Limestone .... 
 
 15,000 
 
 18,000 
 
 13,000 
 
 Sulphuric acid (50 B.) 
 
 1,000 
 
 800 
 
 600 
 
 Ammonic chloride 
 
 500 
 
 400 
 
 300 
 
 The chloride of ammonium is employed to make up for 
 losses in the process, while the sulphuric acid is used for 
 absorption of ammonia. 
 
 Honigmann has been chiefly instrumental in intro- 
 ducing the process into Germany, and he works in a 
 somewhat different way to Solvay, under whose patent the 
 
RECOVERY OF THE AMMONIA. 163 
 
 works at North wich are conducted. Honigmann's pro- 
 cess is in work at Vagy and Bocsko, but late advices 
 from Germany are to the effect that the process does not 
 pay so well as was anticipated. 
 
 It is said that the plant required by either form of 
 this process is very delicate and liable to get out of order, 
 while it is also stated that for every ton of alkali pro- 
 duced, 5 per cent, of the ammonia used in the prepara- 
 tion is lost. Glassmakers have urged as an objection to 
 the soda ash so made, that it is bulky ; but at the same 
 time it is very pure, as is shown by the following analysis 
 of a sample by Mr. John Pattinson : 
 
 Carbonate of sodium . . . . 9 8 '72 
 Sulphate of sodium . . . .0-20 
 
 Chloride of sodium . . . . .0.54 
 Carbonate of lime . . . . . O13 
 Carbonate of magnesium . . . . 0*04 
 Peroxide of iron . . . . O'Ol 
 
 Alumina ...... O'Ol 
 
 Silica 0-09 
 
 Moisture 0'32 
 
 100-00 
 Sold by English alkalimetrical test . . 5 8 '50 
 
 In the process we have just described, there is ob- 
 tained a solution of chloride of ammonium, and from 
 this the ammonia has to be re-obtained. Originally lime 
 was employed for this purpose, but recently (1872) Mr. 
 Weldon has patented the use of magnesia for this pur- 
 pose. In this way there is obtained magnesium chloride 
 this may be evaporated down to a low bulk, and then 
 heated in a furnace with steam, whereby hydrochloric 
 acid is generated, and may be absorbed in the ordinary 
 
 x 2 
 
164 THE ALKALI TRADE. 
 
 Gossage towers, while magnesia remains in the furnace, 
 and may be used over and over again. 
 
 In a later patent (1873) Mr. Weldon claims the use 
 of artificial carbonate of magnesium for the same pur- 
 pose, but the method of procedure is somewhat different. 
 In this case the chloride of ammonium liquors are distilled 
 with the carbonate, thus giving a distillate of ammonic 
 carbonate, and leaving behind chloride of magnesium. 
 The magnesia obtained from the latter he converts again 
 into carbonate by suspending it in water, and subjecting 
 the milk to the action of carbonic anhydride from any 
 source. It should be remarked that Mr. James Young 
 had in 1872 patented the use of carbonate of calcium or 
 magnesium for the same purpose, but no method for its 
 constant regeneration as in Weldon's case. 
 
 Finally, we must direct attention to some improvements 
 patented by Mr. James Young in 1871, having reference 
 especially to the plant used in the ammonia process. He 
 employs a series of air-tight vessels, which are so arranged 
 as to admit of revolution, but as this form of plant has 
 not been adopted, so far as we know, we may conclude 
 this notice with a statement of the claims of the inven- 
 tion. These are, the boiling with water of the bicarbonate 
 of soda, mixed with compounds of ammonia, or heating 
 it by steam, so as to reduce it to carbonate of soda, by 
 driving off and recovering a portion of the carbonic acid 
 and the residual compounds of ammonia in the manner 
 described ; and the manufacture of carbonate of soda in the 
 manner described, so that all the ammonia or compounds 
 of ammonia are always kept within air-tight apparatus. 
 
 Whatever success may ultimately attend the ammo- 
 nia process, it is certain that it can only have a limited 
 
DAVIS'S SODA PKOCESS. 165 
 
 application, unless other sources of ammonia are discovered 
 and rendered available. In any case it cannot supersede 
 Leblanc's, for the strength of this process not only 
 consists in its wide existence, but the various bye-pro- 
 ducts have by their utilisation become such important 
 articles of commerce, that if not made in the present way, 
 they must be made in some other way. At the same time 
 the fact remains that there is not only room for improve- 
 ment in this process, but that the desideratum of the day, 
 is a process which shall furnish in one, soda and chlorine, 
 or soda and hydrochloric acid. 
 
 In the meantime we would direct attention to a new 
 process for making soda arid phosphate of soda, patented 
 and worked out by Mr. Gr. E. Davis, of Manchester, which 
 is the more interesting inasmuch as it avoids the nuisance 
 arising from alkali waste. 
 
 It has for one of its objects, the utilisation of the 
 several phosphates of alumina in such a way that both 
 the alumina and the phosphoric acid are gained, caustic 
 soda being produced as a bye-product, or if the caustic 
 soda be made the principal manufacture, the phosphate of 
 lime and the aluminous residue will be the bye-products ; 
 and as the process is one which is likely to receive the 
 attention of manufacturers, manufacturing as it does soda 
 without the production of a noxious waste, we give our 
 readers a description of the process. 
 
 A mixture is made of phosphate of alumina, sand, 
 salt-cake, and slack, all in the state of powder, and the 
 mass heated in an ordinary black ash furnace until the 
 decomposition is complete, which happens in rather less 
 time than with an ordinary black ash ball, as the mixture 
 only requires heating to strong redness, and need not be 
 
 II7SRSITTS 
 
166 THE ALKALI TRADE. 
 
 in any way fluxed ; indeed, it is almost impossible to flux 
 a charge in any ordinary length of time. When the de- 
 composition is complete, the charge is drawn into an iron 
 bogie, and even without cooling is ready for the operation 
 of lixiviation. 
 
 The best form of sand to use for this process is that 
 which comes from the grinding and polishing of plate 
 glass, which, being a waste product, costs the glass-works 
 a large sum of money annually to remove. 
 
 The sulphurous acid arising from the decomposition 
 of the salt-cake escapes from the furnace, and may be 
 utilised for the production of salt-cake by Hargreave's 
 process, or in the manufacture of sulphites, by performing 
 the heating of the charge in what is known as a close 
 roaster; if the gas be not required, the charge may be 
 heated in an ordinary furnace or revolver. Several 
 charges worked on the large scale in an ordinary hand 
 black ash furnace were compounded as follows : 
 
 Phosphate of alumina . . . .1*5 cwt. 
 
 Salt-cake 2-75 
 
 Waste sand 0'75 
 
 Slack 0-75 
 
 Each charge was worked and drawn in less than an hour, 
 and was so thoroughly decomposed that only traces of 
 phosphate of alumina were found in the insoluble 
 portion. 
 
 The chief reaction which takes place, is the formation 
 of a double silicate of alumina and soda, and the soluble 
 tribasic phosphate of soda. The reaction may probably 
 be represented as follows : 
 
 A1P0 4 + 2(Na a S0 4 ) + C a + Si0 2 = 
 (NaAlSi0 4 ) + Na 3 P0 4 + 2(S0 2 ) + 2(00) 
 
MANUFACTUKE OF PHOSPHATE OF SODIUM. 167 
 
 After leaving the furnace, the mass is lixiviated in the 
 ordinary vats used in the alkali manufacture, and a solu- 
 tion of tribasic phosphate of soda is easily obtained. The 
 insoluble residue remaining behind, consisting of the 
 double insoluble silicate of alumina and soda, and con- 
 taining also a little sulphide of iron, free sand and cinders 
 from the slack used, is very easily washed, and is very 
 coarse and open in whatever way it is manipulated. It- 
 has absolutely no smell, and no smell is eliminated in 
 whatever atmosphere it is placed or kept. 
 
 The solution, or as we may term it the vat-liquor, is a 
 solution of tri-sodic phosphate, which may be easily con- 
 verted into the ordinary or rhombic phosphate by the 
 addition of phosphoric acid, thus 
 
 2(Na 3 P0 4 ) 4- H 3 P0 4 =3(Na 2 HP0 4 ) ; 
 
 which may be purified by recrystallisation. Caustic soda 
 is made by acting on the vat-liquor with quicklime, when 
 the following reaction takes place 
 
 2(Na 3 P0 4 ) + 3(CaO) + 3(H 2 0)=(Ca 3 (P0 4 ) 2 ) + 6(NaHO). 
 The causticising of a phosphate liquor can take place at 
 higher densities than in the present process, thereby 
 saving much fuel. The lime-mud in this case is no 
 nuisance ; it is a phosphate of lime of great purity, and 
 only requires partially drying to make it fit for the 
 market, where it will fetch, as an 80 per cent, article, 
 about 6/. per ton. After causticising, the liquor is 
 worked in just the same way as hitherto, that is to say, 
 evaporated, the salts fished out, and the caustic soda 
 carried to cream or fusion. Carbonate of soda is made 
 by acting upon the tribasic phosphate of soda with pow- 
 dered chalk, thus 
 
 2(Na 3 P0 4 ) + 3(CaC0 3 )=Ca 3 P 2 8 + 3(Na 2 C0 3 ). 
 
168 THE ALKALI TRADE. 
 
 The insoluble residue, which has been mentioned be- 
 fore as not being in any way noxious, may be piled in 
 heaps, and the sulphide of iron allowed to oxidise, after 
 which the copperas may be washed out, and the iron-free 
 residue used for alum making, or other applications, such 
 as sewage precipitation, etc. It dissolves easily in all the 
 dilute acids, forming salts of alumina and soda, and gela- 
 tinous silica. 
 
 Thus it will be seen that this process deserves the 
 earnest attention of manufacturers, for not only may it 
 produce soda, at a cheaper rate than hitherto, but there 
 is no noxious waste to deposit, and what waste there is, 
 may be used up profitably. The process may be carried 
 on in any alkali works without any change of plant ; and 
 as far as we know at present, it is the only feasible process 
 for making alkali, which both prevents the formation of a 
 noxious waste and the recovery of nearly the whole of the 
 sulphur. The process, moreover, as one for producing 
 phosphate of soda, contrasts favourably with the method 
 at present in practice. This is as follows : Coprolites 
 are ground to powder and stirred with sulphuric acid of 
 28 Tw.; the sulphate of calcium so formed is allowed to 
 deposit, and the supernatant liquors are drawn off, neu- 
 tralised by the addition of soda ash, and crystallised. 
 The product on recrystallisation gives commercial phos- 
 phate of sodium. 
 
HISTORICAL NOTES OX SOAP. 169 
 
 CHAPTER XT. 
 
 MANUFACTURE % OF SOAP. 
 
 THE history of the soda trade would be imperfectly de- 
 scribed, did we not bestow some attention on the applica- 
 tion of caustic soda to soap making. In this place we 
 shall give only a few historical notes regarding this 
 manufacture, and the salient features of the process, re- 
 ferring our readers for full descriptions to the admirable 
 treatises already existing. 
 
 According to Bod well, soap is first mentioned by 
 Pliny, who declared it to be a Gallic invention, and at 
 that time best prepared in Germany. Pliny seems also 
 to have distinguished between hard and soft soap, and 
 was acquainted with the mode of its preparation from 
 wood ashes (beech tree) and goat's tallow. Bodwell says 
 it was used solely as a kind of pomatum, while for 
 cleansing purposes the Greeks added wood ashes (con- 
 taining carbonate of soda) to the water. This would 
 likewise be inferred from Scripture references, as, for 
 instance, ' Though thou wash thee with nitre and take 
 much soap, yet thine iniquity is marked before me.' 
 (Jeremiah ii. 22). ^Etius, a Christian medical writer, 
 about the end of the fourth century, speaks of a black 
 soap, and Paulus .ZEgineta, a Greek physician in the 
 early part of the seventh century, says he made an ex- 
 temporaneous soap from oil and the burned dregs of 
 
170 THE ALKALI TRADE. 
 
 wine. We have already pointed out that in the ruins of 
 Pompeii, a soap-boiler's shop, containing soap, was dis- 
 covered and excavated. 
 
 In 1795 the Committee of Public Safety in France, 
 engaged Darcet, Lelievre, and Pelletier to investigate the 
 nature of the art of soap-making, and to supplement their 
 studies by devising improved processes founded on che- 
 mical knowledge. In this way many improvements 
 were introduced into the trade, but in those days, as we 
 have seen, the chief sources of soda were kelp and barilla, 
 which were impure forms of sodium carbonate. Before 
 the soap-maker could use these preparations, they had to 
 be dissolved in water and causticised by lime. This 
 was done by the soap-maker himself until caustic soda 
 became a manufactured product, and even nowfln many 
 cases, the soap-maker purchases soda ash and >cauticises 
 it himself. Pearlashes and American potashes are used 
 for making soft soaps, while for the manufacture of hard 
 soap, caustic soda is employed. 
 
 Before proceeding to the description of the manu- 
 facture, it will be well to understand, in the first place, 
 what is meant by the term ' soap.' In chemical language 
 a soap is a salt of a fatty acid, but for a soap to admit 
 of use as a cleansing agent, it must be one which is solu- 
 ble in water, and, to an extent, decomposable by it. Such 
 soaps are those having potassium, sodium, and ammonia as 
 their bases, but the two former are the ones which are 
 made on a large scale. 
 
 Fats and fixed oils constitute the sources from which 
 the fatty acids are derived ; these do not exist in the 
 free state, but in combination with glycerine. To under- 
 stand this clearly, it may be stated that glycerine is a 
 
THE CONSTITUTION OF FATS. 171 
 
 triatomic alcohol, C 3 H g (HO) a , or it may be viewed as a 
 triacid base, and as it exists in fats and fixed oils, the 
 hydroxyls are replaced by the radicals of fatty acids ; 
 thus, with stearic acid we have the compound 
 
 ^0 2 
 
 ^a-H-K J OioMosUf 
 
 352 
 
 Similar compounds, or fats, are formed by glyceryl and 
 the radicals of palmitic, margaric and oleic acids, etc., 
 and the reaction by which they are produced may be 
 exemplified as follows : 
 
 Glycerine + Stearic acid = Tristearine + Water 
 + 3C 18 H 36 2 =C 3 H 5 (C 18 H 35 2 ) 3 +3H 2 0. 
 
 In butter, a fat occurs which may be termed tribu- 
 tyrine C 3 H 5 (C 4 H 7 2 ) 3 ; the fats occurring in the human 
 body and in animal food are tripalmitine C 3 H 5 (C 16 H 31 2 )3, 
 and tristearine C 3 H 5 (C 18 H 35 2 ) 3 . Trioleine, a more fluid 
 fat abounds in the oils extracted from the lower animals 
 and vegetable seeds ; its formula is C 3 H 5 (C 18 H 33 2 ) 3 . The 
 residues from these vegetable matters are known as oil- 
 cakes, and they are largely used for cattle feeding. 
 
 Now when these fats or fixed oils are melted and 
 boiled with caustic alkali, a reaction takes place, which 
 may be represented by the following example : 
 
 Mutton suet + Caustic soda = Glycerine + Stearate of sodium 
 QjSffiS&^Vdi + 3NaHO =C 3 H 5 (HO)" 3 + 3C 18 H 35 Na0 2 
 
 that is to say, the fat is decomposed by the caustic alkali, 
 giving, in the instance we have adduced, glycerine and 
 stearate of sodium. The process itself is called ' saponi- 
 fication,' the product is ' soap/ while the glycerine is a 
 bye-product. This glycerine is for the most part thrown 
 
172 THE ALKALI TRADE. 
 
 away, but a considerable quantity is made pure and used 
 for the manufacture of nitro-glycerine. 
 
 Soaps are known as hard, soft, or silicated. Hard 
 soaps result from the use of soda, while soft soaps are 
 produced by using potash ; of silicated soaps we shall 
 have more to say anon. 
 
 Hard Soaps are manufactured from tallow, palm oil, 
 cocoa-nut oil, resin, etc., by saponification with caustic 
 soda. 
 
 It will be well here to point out that the consistence 
 of a neutral fat depends upon the predominance of olein 
 or stearin, the first of these bodies being liquid and the 
 second solid. 
 
 The pans in which the saponification is effected vary 
 in size, some being 15 feet in diameter and 15 feet deep, 
 capable of yielding 25 to 30 tons of finished soap in one 
 operation. They are constructed of wrought-iron plates, 
 which are riveted together and heated either by a steam 
 pipe immersed in the contents, or by a steam jacket, or 
 by fire. The manufacturer charges his pan with neutral 
 fat or oil, and adds caustic lye of 1-05 specific gravity, 
 boils and stirs. This produces a milky emulsion, to 
 which are added fresh quantities of soda lye, each portion 
 being stronger than the preceding one, until there is free 
 alkali present. These processes are repeated until the pan 
 is filled, but finally the alkali must not be in excess. 
 
 Common salt is now added in the proportion of 10 Ib. 
 to every 100 Ib. of fatty matter used, with the view of 
 salting out (or rendering insoluble) the soap produced, 
 which thereupon floats in granules. 
 
 The spent lye is next drawn off and discharged, while 
 the soapy mass is boiled with fresh weak lyes. This 
 
SOAP MAKING. 173 
 
 operation gives a homogeneous mixture, which is allowed 
 to remain quiescent for a few hours, after which it is 
 solidified in rectangular frames of cast-iron plates, and 
 after four to five days, when hardened, it is cut by wires 
 into slabs or bars. 
 
 Soft Soaps are made chiefly from whale, seal, and 
 linseed oils, tallow and resin, in this country ; while on 
 the Continent, hemp, linseed, and poppy oils (drying oils), 
 rape and train oils are largely employed. 
 
 These are saponified by potash lyes until a streaky 
 appearance is observed, after which the product is clari- 
 fied by stronger lyes, till it presents itself as a transparent 
 slime ; much of the water is evaporated off, and the 
 boiling continued, meanwhile stirring with sticks until it 
 ' talks.' It is then packed in casks as a deliquescent 
 paste. 
 
 Soap from Resin is obtained both as hard and soft, 
 according to the process employed. Eesin itself is a 
 mixture of pinic and sylvic acids, together with colo- 
 phonic acid ; these are highly oxidised products of tur- 
 pentine, and considerable quantities are obtained as a 
 residue in the distillation of turpentine. 
 
 The resin is first purified and decolourised by distilla- 
 tion in a current of steam, after which it may be used 
 alone, or mixed with fats. The production of soap from 
 resin is easily explained, resin soaps being simply the 
 alkaline salts of the acids contained in resin. These acids 
 are capable of decomposing sodic carbonate. In short, a 
 soap may be said to be commercially a body which, on 
 treatment with water, liberates alkali. This is effected 
 with ordinary soaps as follows : The water decomposes 
 the neutral sodic or potassic salt into free alkali and acid 
 
174 THE ALKALI TRADE. 
 
 salt, which latter, being insoluble, is precipitated as ' suds ' 
 while the alkali goes into solution, and by its action upon 
 fatty impurities, effects the cleansing which is desired. 
 This is not at all difficult to comprehend, if it be borne 
 in mind that soap is a polybasic salt, capable of resolu- 
 tion into a less basic or more acid salt, and free base. 
 
 Soap from Yolk of Eggs. Bicharclson and Watts 
 state that in the print-works of Alsace, there are con- 
 sumed annually 125,000 kilogrammes of dry albumen, 
 and one kilogramme requires the whites of 28 eggs. The 
 yolks are now used for soap-making as well as for other 
 purposes. To understand the production of soap from 
 the yolk of eggs, we must look into its chemistry. 
 
 Besides the olein contained in the free state, there is 
 present a body called lecithine, of formula C^H^NPOg. 
 Gobley, Diakonow, Strecker, Thudichum, and Kingzett 
 have studied this substance, and express its chemolysis as 
 follows : 
 
 Glycerophosphoric Oleic Palmitic 
 
 Lecithine. Water. acid. Choline. acid. acid. 
 
 C 42 H 84 NP0 9 - 3H 2 = C 3 H 9 P0 6 + C 5 H J5 N0 2 + C 18 H 34 2 + C 16 H 3 ,0 2 
 
 That is to say, bases have the power, by abstracting 
 water, to split up lecithine into, among other products, 
 oleic and margaric acid ; so that when eggs are used for 
 soap-making, this process actually occurs, the soda or 
 potash employed, being sufficient to effect the necessary 
 decomposition, and the resulting soap being therefore the 
 product from not only the olein, but from the fatty acids 
 so formed. 
 
 Mottled Soaps are produced spontaneously, or by 
 adding to the nearly finished soap, crude soda liquor con- 
 taining sulphide, through a watering spout. On descend- 
 ing through the pasty mass, any iron that may be present, 
 
SILICATED SOAPS. 175 
 
 is seized and precipitated in veins, thus presenting in the 
 soap the appearance of marble. Or, instead of this pro- 
 ceeding, a slight addition of prussian-blue is made to the 
 soap. In France, sulphate of iron is added during the 
 boiling, by which means ferrous oxide is first formed, and 
 this rapidly peroxidises and gives rise to the mottled 
 character in a great degree. Mottling is simply a trade 
 practice, and serves no useful purpose. 
 
 Hard Soaps, when genuine, have the following com- 
 position : In the case of mottled soap, 20 per cent, 
 water ; in white, equal 25 per cent.; and in yellow, 30 
 per cent, together with 8 to 9 per cent, alkaline bases, 
 and 60 to 70 per cent, of fat acids. (Eichardson and 
 Watts.) 
 
 Soft Soap is generally used for ' fulling ' and for 
 cleansing and scouring woollen stuffs. It has a composi- 
 tion which is expressed by the following analyses given 
 bv Eichardson and Watts : 
 
 Analyses of soft soaps 
 
 i 
 
 2 
 
 Fatty acid 
 Potash 
 
 50-0 
 11-5 
 
 40-0 
 9-5 
 
 Water ...... 
 
 38-5 
 
 50-5 
 
 Silicated Soaps. We have remarked that, commer- 
 cially, a soap is not necessarily the alkaline salt of a fatty 
 acid, but a salt of an alkaline base, giving with water 
 free alkali. We may, therefore, in the future, look for- 
 ward to the extension of the soap trade in fresh direc- 
 tions, as chemical laws may dictate. Already the manu- 
 facture of sihcated soap in the hands of Mr. Gossage has 
 assumed a most important magnitude. 
 
 Silicate of soda (or soluble glass) is known, like soap, 
 
176 THE ALKALI TRADE. 
 
 to hold its alkali in but feeble combination, and it pos- 
 sesses considerable detergent power. When mixed with 
 ordinary soap, it forms a mixed soap of greatly reduced 
 price, which is very useful both for domestic and manu- 
 facturing purposes. 
 
 For hard soap, Mr. Gossage melts in a reverberatory 
 furnace nine parts of soda ash containing 50 per cent, 
 caustic soda, with eleven parts of clean sand ; and for 
 soft soap, equal weights of carbonate of potash and sand. 
 These products are dissolved by suitable processes, and 
 mixed mechanically with soap paste, forming the so-called 
 ' silicated soaps.' 
 
 Illustrative of the imperfect knowledge possessed by 
 many manufacturers, we may relate here an appropriate 
 case. A Lancashire soap-maker, aware that Mr. Gossage 
 bought sand for soap-making, also determined to buy 
 some, but when he had purchased it he was at a loss to 
 know how to use it, and in consequence mixed the sand 
 with his soap paste ! 
 
 Thus far we have attempted to indicate the steps 
 in the processes of soap-making, but the chapter is neces- 
 sarily little more than an indication of the various plans 
 and processes now in use. In conclusion, we give here 
 some statistics relative to the soap trade. 
 
 In the year in which the duty on soap was abolished 
 (1852), the total production of soap in Great Britain was 
 equal to 1,600 tons per week, ' less than one-half of 
 which was produced in Lancashire ' (Gossage). In 1860, 
 no less 'than 9,749 tons were exported, but the export 
 trade has fallen off since. In the year 1870 the produc- 
 tion of soap in the Lancashire district alone, amounted to 
 the total production of 1852; therefore, to 1870, it had 
 
SOAP STATISTICS. 
 
 177 
 
 increased 50 per cent. (Gossage). The following figures 
 are taken from McCulloch's Dictionary, and show the 
 quantities of soap produced in England and Scotland : 
 
 YEAR ENDING JANUARY 5, 1872. 
 
 Kind of soap 
 
 England 
 
 Scotland 
 
 Silicated . ... 
 Hard 
 Soft 
 
 1,320,033 
 169,519,201 
 11,874,932 
 
 Ib. 
 
 7,150 
 15,206,064 
 7,150,119 
 
 182,714,166 
 
 22,363,333 
 
178 THE ALKALI TRADE. 
 
 CHAPTEE XII. 
 
 HISTORICAL NOTES ON THE BLEACHING INDUSTRY. 
 
 MR. PARKES, in his ' Chemical Essays/ gives some inter- 
 esting observations on the history of bleaching. He re- 
 cords that Pliny wrote, ' Of late days there were seen in 
 the amphitheatres of the Emperor Nero, fine curtains of 
 blue azure colour like the sky, and the very floor of the 
 ground under men's feet was coloured red. But for all 
 these paintings and rich dyes, yet, when all is done, the 
 white linen held the pre-eminence still, and was highly 
 esteemed above all colours.' Pliny likewise records that 
 the Gauls and Britons of his time were acquainted with a 
 mode of bleaching linen cloth, by pounding the woven 
 yarn in water, and beating it upon a smooth stone 
 with broad-headed cudgels ; he also tells us that ' the 
 Faventine cloth is always far whiter than the Allian, 
 which is ordinarily brown when it is new woven and 
 before it is bleached.' Theophrastus (son of a fuller in 
 the Isle of Lesbos, 300 B.C.) relates that lime was then 
 employed in bleaching ; moreover, there are numerous 
 allusions in Scripture to fine linen white and clean. The 
 ancients employed sulphurous acid for bleaching pur- 
 poses. 
 
 Passing from these very ancient times to modern ones, 
 we find that, in 1803 (according to Mr. Henry Ash- 
 worth), the charge for bleaching a well-known description 
 
THE PROCESS OF BLEACHING. 179 
 
 of cloth was 7s. Qd. for a piece of 28 yards ; such a piece 
 would now cost less than 6d. for bleaching. Half a cen- 
 tury ago, the linen from Holland was the most esteemed, 
 owing to the superior skill there employed in the opera- 
 tions of bleaching. Generally, the process employed at 
 and before that time may be thus described : The goods 
 were steeped in water, or hot dilute alkaline lyes, after 
 which they were boiled in similar solutions, which opera- 
 tion was known as ' bucking.' This done, the goods were 
 exposed to the air on the grass (crofting), and after they 
 had been exposed sufficiently long they were immersed 
 in sour milk (souring), and the whole of the operations 
 repeated as often as was necessary. Sometimes these 
 operations extended over a period of six, seven, or even 
 eighteen months. 
 
 But an improvement was near at hand, and consisted 
 in the employment of sulphuric acid in the place of sour 
 milk. Although the manufacture of sulphuric acid was 
 first successfully introduced by Dr. Eoebuck, as we have 
 already shown, the application of it to bleaching purposes 
 was the proposition of Dr. Home. In this way, the time 
 required for the above operations was reduced to four 
 months or so. In 1774, the Swedish chemist, Scheele, in 
 experimenting on the action of marine (hydrochloric) 
 acid upon native manganese, discovered the green gas 
 chlorine, and he himself afterwards ascertained its power 
 of destroyiog vegetable colours, either when employed 
 as a gas, or in the form of an aqueous solution. Davy, 
 in 1810, proved its elemental character, and changed its 
 name from oxy-muriatic acid to chlorine. Berthollet, in 
 1785, advocated its employment in the art of bleaching, 
 and not only so, but he described experiments illustrative 
 
 2 
 
180 THE ALKALI TRADE. 
 
 of the bleaching character of chlorine on pronounced 
 vegetable colours. 
 
 To understand this bleaching action, it must be stated, 
 that it is dependent on the decomposition of water by 
 the chlorine, which liberates nascent oxygen, and this is 
 what really effects the bleaching. Indigo blue, in the 
 presence of water, is destroyed by chlorine with the for- 
 mation of a soluble orange-red non-tinctorial principle, 
 viz. Isatin, thus 
 
 C1 2 + H 2 + C 8 H 5 NO=2HC1 + C 8 H 5 N0 2 . 
 
 ' Thus bleaching by the action of chlorine, like bleaching 
 by exposure to air, is really an act of oxidation ' 
 (Odling). 
 
 About the end of July, 1787, the first actual applica- 
 tion of chlorine to bleaching was effected by Messrs. 
 Milnes and Messrs. Gordon, Barrow, and Co., ot Aberdeen, 
 on the information given by Professor Copland and the 
 Duke of Gordon, who gained their knowledge on the 
 Continent. Mr. Watt, the engineer, on the invitation of 
 Berthollet, witnessed his experiments about the same 
 time, and he communicated the results to his relative, Mr. 
 MacGregor, of Glasgow, who continued the experiments, 
 and used the process. But, after some experience, it 
 became important to protect the fibre of the material to 
 be bleached, from the corrosive action of chlorine itself 
 and the hydrochloric acid which is produced simultane- 
 ously with the act of bleaching. 
 
 This, and the injurious action of the chlorine upon the 
 workmen, led to the use of ' lye of Javelle,' which was 
 introduced from Javelle, near Paris, where it was origi- 
 nally made in 1792, and which was really hypochlorite 
 
HISTORICAL NOTES ON BLEACHING POWDER. 18] 
 
 of potassium. But this was destined to give way, after 
 some extended use, to Mr. Tennant's patent of 1798, in 
 which a solution of hypochlorite of calcium was used, 
 although Dr. Henry appears to have first used lime. Mr. 
 Tennant shortly afterwards lost the right of patent, but 
 in 1799 he introduced the use of bleaching powder. 
 Bleaching powder is still used in vast quantities, its manu- 
 facture having greatly developed since the introduction 
 of straw, Esparto grass, etc., in addition to rags, for the 
 manufacture of paper. 
 
 The further history of bleaching powder relates to 
 the improvements in the manufacture of chlorine used 
 in its preparation. These will be described in detail in 
 further chapters. Here we shall merely give the rationale 
 of the process of bleaching. 
 
 In the case of calico, the fabric is well washed and 
 boiled successively with lime-water, much dilute sulphuric 
 acid, and weak caustic soda, to remove the weavers' 
 dressing, greasy and resinous matters, etc. It is then well 
 washed and digested in a 2 to 2J> per cent, solution of 
 bleaching powder, after which it undergoes an immersion 
 in very dilute sulphuric acid, which liberates chlorine 
 within the fibres, and thus removes the colour in situ. 
 But even now it is not perfectly white, and is therefore 
 washed and again steeped in an alkaline lye, to remove 
 the colouring matter rendered soluble by the chlorine. 
 It is then again passed through weaker solutions of 
 bleaching powder and dilute acid successively, and finally 
 thoroughly washed in copious streams of water, to 
 effectually remove the sulphuric acid, which would other- 
 wise destroy the fibre. 
 
 Bleaching powder presents a great facility of manage- 
 
182 THE ALKALI TRADE. 
 
 inent and capability of being used in different ways, so 
 much so, that the great development of the manufacture 
 is considerably due to these causes. 
 
 Now let us pause for a time to consider the constitu- 
 tion of bleaching powder, and the probable manufacture 
 in the future of that principle in it in which rests its 
 whole power of bleaching. 
 
 Bleaching powder, then, has, by the researches of Gay- 
 Lussac, Kolb, Kingzett, and others, been proved to be 
 a compound of hypochlorite and chloride of calcium, 
 represented by a formula first assigned to it by Odling, 
 
 Ca ; but the combination is so feeble that, under 
 
 (ULd 
 
 certain conditions, water destroys the compound from a 
 chemical whole into the two salts. Till quite recently, 
 however, the true hypochlorite of calcium was unknown 
 in the solid pure state, but the author has succeeded in 
 the isolation of the hypochlorite from bleaching powder, 
 thus still more clearly establishing the constitution of 
 bleaching powder. 
 
 Bleaching powder as we know it in commerce, is 
 a mixture of the above principle, with a great excess of 
 lime, and contains about 35 to 38 per cent, chlorine. 
 For bleaching purposes, the excess of lime is valueless, 
 so also is any excess of chloride that may be present, 
 and also that amount of chlorine which enters as 
 chloride into the compound molecule. That is to say, 
 the bleaching power may be said to reside in the hy- 
 pochlorite of calcium only ; so that if it were possible 
 to manufacture pure calcic hypochlorite, its use would 
 supersede that of ' bleach,' among other reasons, because 
 (l)it is entirely and easily soluble in water, and (2) it 
 
BLEACH-LIQUOR. 183 
 
 possesses the total bleaching power of the powder in a 
 much less volume. 
 
 In a following chapter we shall point out how, in the 
 future, the manufacture may be possibly conducted in 
 this way. As we have already shown, ' bleach ' must, 
 before being used, be dissolved in water ; but as by the 
 passage of chlorine into milk of lime there is obtained a 
 product richer in chlorine than the powder, bleaching 
 liquor continued to be produced and used for some time 
 after the invention of the powder. The objection to it, 
 lies in its anti-portable nature, and this objection was 
 more serious in those days than now, because even the 
 action of chlorine upon milk of lime (except under limited 
 conditions) was unknown, and if excess of chlorine hap- 
 pened to be used, free hypochlorous acid was produced, 
 and thus a product obtained, which is liable to explode 
 spontaneously ; but if the action of chlorine be limited in 
 the manner to be hereafter described, this danger is 
 avoided. 
 
134 THE ALKALI TRADE. 
 
 CHAPTEE XIII. 
 
 OLD PROCESSES OF MANUFACTURING CHLORINE. 
 
 IN a previous chapter we have described the manufacture 
 of hydrochloric acid as a bye- product obtained in the 
 conversion of salt into sulphate of sodium, together with 
 the means of condensation employed and the working 
 results. 
 
 Let us now consider this hydrochloric acid as a source 
 of chlorine, for the production of bleaching powder and 
 chlorate of potassium. These, however, are not the only 
 manufactures in which hydrochloric acid is found useful. 
 It is used by bleachers for decomposing tbe lime soap 
 formed by boiling greasy fabrics with lime, the fatty 
 acids so liberated being removed by alkali. The dyer 
 also employs it for making chloride of tin, and it is 
 largely used as a solvent for the phosphatic constituents 
 of bone during the manufacture of gelatin, We might 
 easily extend this list of the uses of hydrochloric acid, 
 but we will simply add that in some alkali works, 
 hydrochloric acid is employed to generate carbonic acid 
 from limestone, to make bicarbonate of sodium. 
 
 We shall first describe the manufacture of chlorine 
 as carried out on the largest scale, prior to the introduction 
 of Mr. Weldon's first process, after which we shall describe 
 Dunlop's, Shank's, and other processes which were either 
 actually in work to a greater or smaller extent, or have 
 
MANGANESE ORES. 185 
 
 been only suggested. Ever since the discovery of chlorine 
 by Scheele, by the action of muriatic acid upon peroxide 
 of manganese, that method has been the one in use on 
 the largest scale for the manufacture of chlorine. 
 
 The manganese ores employed, are derived chiefly 
 from Germany, Spain, France, Belgium, and Holland, and 
 small quantities are produced in England and America. 
 ' Pyrolusite ' is the most abundant of these ores, and one 
 of the richest in oxygen, containing from 80 to 87 per 
 cent, red oxide of manganese, and 10 to 14 per cent, 
 oxygen. This is important to bear in mind, because the 
 generation of chlorine depends essentially upon the seizure 
 of the hydrogen of the hydrochloric acid, by the excess 
 of oxygen in the pyrolusite, to the formation of water, 
 with the liberation of the chlorine. The ores used in 
 commerce generally contain from 60 to 75 per cent, in 
 terms of Mn0 2 (peroxide of manganese). 
 
 In the early days of the trade, our chief supplies came 
 from Devonshire, then Germany and Belgium fed the de- 
 mand ; but of late years the best qualities and chief quan- 
 tities have been imported from Spain. Kichardson and 
 Watts, in their work, tell us that the total production of 
 manganese ores in Germany amounted in 1857 to 895,666 
 centner (mostly from Nassau), and that Spain produced 
 annually 500,000 centner. Muspratt, in his Dictionary, 
 states the total consumption in this country to be about 
 25,000 tons annually, of which from 17,000 to 18,000 
 tons were in his days, used in the mauufacture of bleach- 
 ing powder. For 1858, Ure gives our total import of 
 manganese as 24,171 tons. 
 
 The chlorine was originally produced from a mixture 
 of salt, manganese and sulphuric acid, heated in a leaden 
 
186 THE ALKALI TRADE. 
 
 apparatus on a water bath. The proportions used in 
 1800 were as under : Vitriol, 4 ; manganese, 2 ; water, 
 4 ; salt, 44. (Mactear.) 
 
 Up to 1815 an excise duty of 30/. per ton was laid 
 upon the waste products from bleaching powder stills 
 (Clapham), but after that date, the sulphate of sodium 
 contained in the residuum was extracted and used for 
 alkali making. Eventually the use of salt in admixture 
 with the manganese ore was abandoned, and the latter 
 used alone. For the reaction, bitubulated stoneware 
 carboys were used, but these gave way many years ago 
 to perforated stoneware cylinders; then came cast-iron 
 vessels lined with lead, and eventually a more recent kind 
 of still, which was sometimes hewn out of the solid stone. 
 
 The most recent kind of still (as used in the Weldon 
 process) is, therefore, the perfected form of an apparatus 
 which, though very crude originally, has undergone im- 
 provements in construction, partly by Lee and Pattinson 
 (1846), and finally by Weldon. These stills are now 
 constructed of Yorkshire flagstones, being square in 
 build, and of about 5 to 6 feet. The joints are rendered 
 air-tight by means of indiarubber rods supplemented 
 by Chinese clay and tar, and the whole girded strongly 
 together by iron bands. They are provided with a 
 manhole, large enough to admit a man, for cleansing 
 purposes ; and there are also two taps, a smaller one for 
 testing purposes, and a large one near the bottom for 
 drawing off the residual liquors. The stills are further 
 fitted with a false bottom of stone, 5 to 10 inches from the 
 true bottom, on which (in the case of ore) the charge of 
 manganese is laid 400 to 800 Ib. manganese ore. 
 
 The hydrochloric acid, which is usually stored in a 
 
OLD PROCESS OP CHLORINE MANUFACTURE. 187 
 
 cistern above and near the still, is run into the still 
 through an indiarubber pipe, passing into a hole just 
 large enough to admit it. There is also another small 
 hole for gauging the contents, and in one corner of the 
 still, which is partitioned off by stone, enters the steam 
 pipe for heating purposes. 
 
 Originally, these stills were not uncommonly heated 
 by fire, but explosions often occurred, and led to the dis- 
 use of fire ; moreover, in the Weldon process steam 
 answers thoroughly well, the regenerated manganese 
 being so much more soluble than the ore. The chlorine 
 is led away by an earthenware pipe in communication 
 with a cistern of water which serves the purpose of wash- 
 ing the gas, which then passes on through lead pipes for 
 the chamber use. 
 
 The chemical reaction which occurs in the stills is as 
 follows : 
 
 Mn0 2 + 4HCl = MnCl 2 + 2H 2 + Cl 2 . 
 
 That is to say, one half of the total chlorine was ori- 
 ginally lost (for the residual liquors were thrown away) 
 as chloride of manganese. Not only so, it was impossible 
 to entirely neutralise the whole of the hydrochloric acid, 
 in this way. 
 
 These facts led manufacturers to make what use they 
 could of these residual liquors. We have seen that they 
 were used to decompose alkali waste, for instance. Fur- 
 ther attempts were made from time to time to regenerate 
 at least the manganese contained in them, while other 
 efforts were directed to substitute entirely different pro- 
 cesses. From the many proposed methods we shall 
 select a few for description. 
 
 Mr. Elliott attempted the regeneration of the rnanga- 
 
188 THE ALKALI TRADE. 
 
 nese by evaporating the liquors left in the still, to dryness, 
 and roasting the residue in a current of steam. The 
 hydrochloric acid so formed being condensed, the residue 
 consisted of a mixture of protoxide and peroxide of 
 manganese, which was destined for use in the still 
 again : 
 
 MnCl 2 + Ox + H 2 = (MnOx + Ox) + 2HC1. 
 
 Others precipitated the manganese from the liquors as 
 protoxide by means of lime or other bases, and exposed 
 the product to a red heat with access of air, thus produc- 
 ing a more or less highly oxidised manganese ; but all 
 these plans failed commercially on a manufacturing scale, 
 depending as they did in great measure on the rela- 
 tive cost of coal and manganese ores. Moreover, it is 
 impossible to get above a certain state of oxidation under 
 the given circumstances, and, after all, the value of a 
 regenerated manganese depends, like the ore, upon its 
 state of oxidation the greater the amount of oxygen it 
 contains, the more valuable it is. 
 
 Dunlop's process, however, succeeded better than any 
 other, and indeed, Messrs. Tennant have from the time 
 when the process was first introduced, utilised the whole 
 of their residual still liquors by this method. The great 
 drawback to the process lies in the costly apparatus re- 
 quired ; but when once this is erected, Mr. Mactear con- 
 siders it to be even now the best process of the day in so 
 far as cost and yield of bleach are concerned. 
 
 The difficulty we have named, and the high price of 
 coal on the Continent, have militated against its general 
 adoption. 
 
 The process, which is still worked at St. Eollox, is as 
 follows : The liquors are first freed from ferric oxide, 
 
DUNLOP'S MANGANESE REGENERATION PROCESS. 189 
 
 alumina and silica, by the addition of a little milk of 
 lime, after which they are mixed with finely-divided 
 chalk, which reacts on the manganese chloride as fol- 
 lows : 
 
 MnCl 2 + CaC0 3 - MnC0 3 + CaCl 2 . 
 
 This reaction, by the aid of steam under pressure and 
 heat, is completed in about four hours in boilers. The 
 chloride of calcium liquors are then run off, and the 
 precipitated carbonate of manganese is washed and 
 drained. 
 
 The next operation, which is one of the most beau- 
 tiful in the whole range of industrial chemistry, has for 
 its object the expulsion of the carbonic acid and oxida- 
 tion of the manganese. For this purpose the carbonate 
 is drawn through a furnace in small waggons, in much 
 the same way as glass is annealed. Each furnace holds 
 about forty-eight of these waggons, and is worked at an 
 average temperature of 315 C. ; in forty-eight hours all 
 the water and carbonic acid are evolved, leaving a product 
 of about the composition represented by 2Mn0 2 + MnO. 
 
 M. Laurens proposed to obtain chlorine from cupric 
 chloride by mixing it with sand and heating the perfectly 
 dry mixture in retorts or cylinders of iron lined with 
 clay and charcoal, when at a strong heat cuprous chlo- 
 ride forms and chlorine is simultaneously evolved. From 
 the cuprous chloride the cupric salt is again made, by 
 exposure to air and hydrochloric acid, and the resulting 
 solution, after evaporation to dryness, undergoes once 
 more the primary reaction. Thus we have 
 
 (1) CuCl 2 = CuCl + 01 
 
 (2) 2CuGl + HC1 + = H 2 + 2CuCl 2 
 
 Mr. Gatty had previously proposed and examined this 
 
190 THE ALKALI TKADE. 
 
 process in England, and in Germany M. Vogel did the 
 same, while the last-named observer states that the cupric 
 chloride in this way loses only one-third of its total 
 chlorine. Copper is so expensive (some loss is inevitable), 
 and so great is the wear and tear on the plant, that these 
 objections, considering also the danger arising to the 
 workmen from the fine copper dust, have proved in- 
 surmountable. 
 
 Dr. Gerland and Mr. E. Muspratt obtained cobalt 
 and nickel sulphides from manganese liquors, by means 
 of alkali waste liquors, thus utilising in some degree the 
 soluble sulphides of calcium contained therein. 
 
 Mr. Shank devised a chlorine process which was prac- 
 tically worked in St. Helens, and, in fact, at the date of 
 Messrs. Eoscoe, Smith, and Schenck's report the British 
 Association in 1871, was still in operation. In this pro- 
 cess chromate of lime is decomposed in the stills with 
 hydrochloric acid, when the following reaction occurs : 
 
 2CaCr0 4 + 16HC1 = O 2 C1 6 + 2CaCl 2 + 8H 2 + 01 6 j 
 
 giving a steady supply of chlorine, the last portions being 
 expelled by steam-heating. The residual liquors contain- 
 ing chlorides of calcium and chromium, are diluted with 
 hot water, and neutralised with milk of lime ; more milk 
 of lime is now added, first in quantity necessary for the 
 precipitation of the sesquioxide of chromium, and after- 
 wards a further quantity, sufficient for combination with 
 the chromic acid formed in the next operation. The 
 liquors are settled, and the chloride of calcium solution 
 decanted. The sludge is drained, and when stiff, is 
 thrown into a close furnace maintained at low redness, 
 air meanwhile being admitted through apertures, when 
 
DUNLOP'S CHLORINE PROCESS. 191 
 
 the whole mass is transformed into chromate of lime, 
 ready for use over again. One of the greatest objections 
 to this process is the enormous waste of hydrochloric 
 acid involved. 
 
 Another process, known as Dunlop's, has also been 
 in actual use at St. Kollox since it was first proposed. 
 It consists in decomposing a mixture of nitrate (Chilian 
 or soda nitre) and chloride of sodium in cast-iron 
 cylinders by means of sulphuric acid. The gaseous pro- 
 ducts are made to pass through leaden Woulff's bottles 
 containing sulphuric acid to a depth of 24 inches, this 
 great pressure being necessary to moderate the action in 
 the cylinders. Each cylinder takes 12 cwt. of nitre, 
 and sufficient sulphuric acid of 120 Tw. is used to form 
 the bisulphate of soda : 2NaCl + NaN0 3 + 3H 2 S0 4 = 
 3ISraHS0 4 + C1 2 + 3H 2 + N0 3 (nitrous acid), which is 
 run off as a liquid into a furnace containing common 
 salt, thus producing salt-cake and hydrochloric acid. The 
 charges are worked off in thirty-six hours at a tem- 
 perature of 400 to 500 Fahr. The nitrous acid is 
 absorbed by the sulphuric acid in the condensers, and 
 the hydrochloric acid is condensed, while the chlorine 
 goes to the chambers. The nitrous sulphuric acid is 
 employed in the production of chamber acid. 
 
 Mr. Dunlop also suggested the expulsion of the ni- 
 trous compounds by heat, into a chamber where they 
 meet with a current of sulphuretted hydrogen, giving 
 rise to sulphate of ammonium and sulphur 
 
 2H 2 S + N0 4 = NH 4 S0 4 + S. 
 
 There have been proposed several other processes, 
 alike in many respects to this one of Dunlop. They may 
 
THE ALKALI TRADE. 
 
 be expressed as follows : Hydrochloric acid is decom- 
 posed by nitric acid, giving a lower oxidised form of 
 nitrogen and chlorine. The nitrogen compound takes up 
 more oxygen from the air, and the product is again de- 
 composed by hydrochloric acid, and so on indefinitely : 
 
 2HN0 3 + 6HC1 = 2NOC1 2 + 4H 2 + 01 2 
 2NOC1 2 + 2H 2 = 2N0 2 + 2HC1 
 2N0 2 + H 2 + O = 2HNO 3 , etc. 
 
 However, the precise reactions occurring have not been 
 established, and would vary, in all probability, with the 
 circumstances under which they occur. Nitric acid is 
 an expensive oxidant, and it would therefore be neces- 
 sary to thoroughly and cheaply regenerate it. 
 
 We have already, in an earlier chapter, alluded to 
 Longmaid's process, which produces chlorine so diluted 
 with air and nitrogen as to be unfit for making bleaching 
 powder above 20 per cent. The same objection applies 
 to Thilbierge's proposition. Thilbierge passed air over 
 heated ferrous chloride (FeCl 2 ), thus obtaining ferric 
 oxide and chlorine. Eecently (British Association, 1870), 
 Mr. Hargreaves, of Widnes, has revived this idea. He 
 has a process for separating phosphoric acid from iron 
 ores and cinders, and in this process the slag is dissolved 
 in hydrochloric acid, in which operation, apart from the 
 main object of the process, the protochloride of iron is 
 obtained. Mr. Hargreaves proposed to deal with this 
 by evaporating it to dryness, and then by heating the 
 dried substance in air at a temperature about the melt- 
 ing point of zinc, to decompose it into the peroxide of 
 iron and free chlorine which was to serve for the produc- 
 tion of bleaching powder : 
 
 Fe 2 01 6 + 3 = Fe 2 3 + C1 6 . 
 
VARIOUS CHLORINE-MAKING PROCESSES. 193 
 
 Thus it will be seen that, if the process worked, not 
 only would the use of manganese be dispensed with, but 
 a given amount of hydrochloric acid would produce double 
 the amount of chlorine that can be obtained by using 
 manganese. But even should this be so, and the reactions 
 be fully realised, the process would be attended by an 
 insuperable difficulty the treatment of the dilute chlo- 
 rine produced. Moreover, in these days, when the man- 
 ganese is regenerated, the process would, by comparison, 
 depreciate in value. 
 
 Oxland, in 1845, passed one volume of dry hydro- 
 chloric acid gas and two volumes of air through air- 
 tight reverberatory furnaces, packed with pumice stone 
 kept at a red heat ; and in 1846, Jullion, in a similar 
 plan, substituted asbestos and spongy platinum for the 
 pumice stone. But here again, as in Deacon's process 
 to be presently described, chlorine in a dilute state is 
 obtained. 
 
 Maughan, in 1836, first proposed to pass roaster gas 
 (hydrochloric acid) through manganese contained in 
 cylinders heated by steam, the evolved gases being 
 washed in water and the chlorine conveyed to the 
 chambers ; and, in 1842, Seybel proposed the same pro- 
 cess, only he, moreover, passed his products through 
 water containing manganese in suspension, and kept the 
 manganese in motion. 
 
 Tessie de Mothay has a process which is as follows : 
 Into a retort maintained at a red heat, containing per- 
 oxide of manganese, or a mixture of it with lime, a 
 current of hydrochloric acid gas is caused to pass. Chlo- 
 rine and steam are disengaged, and there remains in the 
 retort, a mixture of undecomposed peroxide of manganese 
 
 Of 
 
194 THE ALKALI TRADE. 
 
 with the chlorides of manganese and calcium. Over the 
 mixture remaining in the retorts, still at the same tem- 
 perature, air or oxygen is passed, which in the presence 
 of the peroxide is said to decompose the manganic 
 chloride at once. 
 
 The chlorine produced in this last operation, is led 
 into vats containing a mixture of lime and protoxide of 
 manganese, which bodies have been previously produced 
 by the decomposition of Mn01 2 by lime, the soluble calcic 
 chloride having been run off. In the vats sesquioxide 
 of manganese and calcic hypochlorite result, and these 
 two react, giving peroxide of manganese and calcic 
 chloride. 
 
 The product, with fresh hydrochloric acid, yields 
 more chlorine for use in the chambers ; or he uses, in- 
 stead of lime, magnesia. Thus he proposes to constantly 
 regenerate the manganese, and get all his chlorine for 
 the production of dry hypochlorites in the pure undiluted 
 condition. 
 
 Some time ago Mr. Deacon secured letters patent 
 for a process which consisted in passing sulphuric anhy- 
 dride and air over salt at high temperatures . 
 
 S0 3 + + 2NaCl = Na 2 S0 4 + C1 2 . 
 
 Unfortunately, air having to be employed, necessarily 
 dilutes the chlorine which is produced, with all the nitro- 
 gen contained therein, even if no other objections were 
 encountered in attempting to realise the above reac- 
 tion. If air be omitted, the following reaction would 
 occur : 
 
 2S0 3 + 2NaCl = Na 2 S0 4 + S0 2 + C1 2 ; 
 
 and directly these resulting gases came in contact with 
 
SUGGESTED CHLORINE PROCESSES. 195 
 
 water, there would be formed sulphuric and hydrochloric 
 acids : 
 
 S0 2 + C1 2 + 2H 2 O = H 2 S0 4 +2HC1. 
 
 F. de Lalande and M. Prud'homme profess to have 
 generalised this reaction of Deacon's, employing in the 
 place of sulphuric anhydride, silicic, boric, stannic, .and 
 phosphoric acids, also alumina. Taking silica, they say 
 that silicate of sodium is formed, together with chlorine, 
 thus : 
 
 Si0 2 + 2NaCl + = Na 2 Si0 3 + C1 2 ; 
 
 and by passing hydrochloric acid over the residue, they 
 obtain re-formed chloride and free silica, for use again : 
 Na 2 Si0 3 + 2H01 = 2NaCl + H 2 + SiO 2 , 
 
 thus obtaining a continuous supply of chlorine. The 
 steam in this last reaction gives rise to two secondary 
 reactions, both of which occur, however, to a very limited 
 extent : 
 
 (1) Clj + H 2 = 2HC1 + 
 
 (2) 2NaCl + H 2 = Na 2 + 2HC1. 
 
 But these methods, so far, are possessed of scientific 
 interest only. In our next chapter we propose to study 
 the process which bears Mr. Weldon's name, and which 
 has proved the most successful industrial process of the 
 day. 
 
196 THE ALKALI TRADE. 
 
 CHAPTEE XIV. 
 
 WELDON'S CHLORINE PROCESS (a). 
 
 TILL quite recently, the numerous attempts made from 
 time to time to regenerate manganese from the acid 
 liquors of chlorine stills were, as we have seen, mostly 
 unsuccessful, the best of them having achieved a very 
 limited adoption. It remained for Mr. Walter Weldon 
 to successfully revive the spent manganese by effecting 
 its aerial oxidation. The importance of this process is 
 borne out by the fact that, taking the total bleach-make 
 of Great Britain during 1874 at 90,000 tons, more 
 than 50,000 were made by Weldon's process. We are 
 informed that in 1874, twenty-two plants were working 
 this process, and that nearly forty others were in course 
 of erection. It is, moreover, largely at work in Ger- 
 many, and is employed at the largest works in France 
 and in Belgium. Eegarding the capability of the plant, 
 it may be said to be limited only by its size. As 
 much as 230 tons of bleach are made per week at one 
 work. 
 
 Incidentally, the process has the advantage of abolish- 
 ing the discharge of corrosive, acid, manganese liquors into 
 water streams, whereby great damage was often effected. 
 The liquors as they come from the still consist of chloride 
 of manganese, containing small quantities of the sesqui- 
 
WELDON'S CHLORINE PROCESS. 197 
 
 chlorides of iron and aluminium, chloride of calcium, and 
 the excess of unneutralised hydrochloric acid. They are 
 run into a well about 7 feet deep, and 20 feet in diameter, 
 provided with an agitator, where they are neutralised by 
 chalk or other forms of carbonate of calcium, thus pre- 
 cipitating the iron and aluminium as oxides, and are 
 afterwards pumped up into the ' settlers.' These settlers 
 are oblong iron tanks, wherein the gypsum and oxides of 
 iron and aluminium deposit, and a clear, pink liquor 
 results ; this is drawn off by means of an iron pipe, 
 provided with a piece of gauze at the extremity, to keep 
 back any solid lumps, and which is allowed to dip just 
 beneath the surface of the liquor. As regards this deposit, 
 it may be said that it causes the only unavoidable loss of 
 manganese in the process, for although the deposit is 
 submitted to washing, yet as thrown away, it contains 
 some manganese. 
 
 A vessel known as an ' oxidiser ' receives the liquors 
 from the settlers. This cylindrical vessel, when of large 
 size, is about 8 to 12 feet in diameter, and 22 to 35 feet 
 deep, constructed of wrought-iron plates, and furnished 
 with two pipes, which go down nearly to the bottom a 
 large one for conveying a blast of air from a blowing 
 engine, and a smaller one for the injection of steam. The 
 oxidiser is also fitted with an agitator. 
 
 The oxidiser, having received a charge of liquor, is 
 heated by steam to somewhere between 150 and 170 
 Fahr. Sometimes the liquors reach the oxidiser at nearly 
 that temperature. Immediately above the oxidiser is a 
 reservoir containing milk of lime (15 to 20 Ib. of the hy- 
 drate to the cubic foot), which is run into the hot liquor as 
 rapidly as possible, air being blown in meanwhile. The 
 
198 THE ALKALI TRADE. 
 
 addition of the milk of lime is continued until the filtrate, 
 from a sample drawn off at a tap placed near the bottom 
 of the oxidiser, ceases to give a manganese reaction with 
 solution of bleaching powder, that is, a purple colour, due 
 to the formation of permanganate of calcium. A certain 
 further quantity of milk of lime is then added, and the 
 blowing continued till peroxidation ceases, which point is 
 usually attained when from 80 to 85 per cent, of the 
 manganese has become converted into peroxide, an opera- 
 tion lasting two to four hours. 
 
 The contents of the oxidiser are now a thin black 
 mud, consisting of chloride of calcium solution, containing 
 in suspension about 2 Ib. of peroxide of manganese per 
 cubic foot, being combined with varying quantities of pro- 
 toxide of manganese and lime. This protoxide of manga- 
 nese and lime are together known as ' base/ and amounts 
 generally to from l to f per cent. The mud is now run 
 into a series of ' mud settlers,' or iron settling tanks, where 
 it subsides to about one-half, so that the top clear liquor is 
 drawn off and discharged, while the mud, now containing 
 about 4 Ib. of peroxide of manganese to the cubic foot, is 
 ready to be charged into the stills, for a fresh operation. 
 For this purpose, the stills are about half filled with the 
 acid, and the manganese mud run in to the extent of 
 about 500 cubic feet to a charge, at the same time that 
 heating by steam is applied. It takes from two to four 
 hours to work off a still. The reactions representing the 
 various operations may be stated generally as follows: 
 
 (1) Mn0 2 + 4HC1 = MnClj + 2H 2 O + C1 2 
 
 (2) MnCl 2 + CaO = CaCl 2 + MnO 
 
 (3) MnO + O = Mii0 2 
 
 We are enabled, through the personal kindness of 
 
THE WELDOISr PLANT. 
 
 199 
 
 Mr. Walter Weldon, to give here a drawing of his chlo 
 rine plant (figs. 21, 22, and 23). 
 
200 
 
 THE ALKALI TRADE. 
 
c c 
 
 X'S MANCiAXESU Ji 
 

 iNEKATlON PLANT (PLAN). 
 
THE OXIDATION PROCESS. 201 
 
 The quantity of lime which it is necessary to employ 
 in the oxidiser varies considerably, because lime dissolves 
 in chloride of calcium, and further, because all parts of the 
 lime do not act equally well the coarser particles act 
 less rapidly and perfectly. Usually, however, 1*15 to 
 1-45 equivalents are added before the precipitation of all 
 the manganese is effected, and the further quantity which 
 is added such that the foregoing figures become 1*5 or 
 1'6 equivalents. 
 
 Now, for one moment, let us consider the use of this 
 additional quantity of lime. The precipitation of pro- 
 toxide of manganese by lime, has for very many years been 
 a well-known fact ; in short, it is the excess of lime 
 employed, which constitutes the very secret of Weldon's 
 process, for without that excess, it would be impossible 
 to carry the peroxidation of the manganese to any great 
 extent. 
 
 In the presence of an excess of lime, there is not 
 obtained peroxide of manganese but, as Weldon suggests 
 and claims to have demonstrated, various compounds of 
 the peroxide with lime, viz., manganites and sesquiman- 
 ganites, etc. Thus CaOMn0 2 and Ca02Mn0 2 are ob- 
 tained, a small portion of the CaO being usually replaced 
 by an equivalent amount of MnO. 
 
 The quantity of air required to be blown in, varies 
 with the conditions, chiefly depending upon the depth of 
 the oxidiser the greater the depth the more rapid the 
 oxidation proceeds. In one instance 175,000 cubic feet 
 of air were blown in, during five hours, and of the oxygen 
 contained in this, 14'8 per cent, (equal to rather more 
 than 4 cwt.) was absorbed in the production of 22 cwt. 
 of peroxide of manganese. (Weldon.) The mechanical 
 
202 THE ALKALI TRADE, 
 
 power generally expended in blowing, averages about 
 between seven and eight horse-power for one hour, per 
 lOOlb. of Mn0 2 made. 
 
 Theoretically, 1,020 Ib. of Mn0 2 should yield the 
 amount of chlorine contained in 1 ton of bleaching 
 powder per 37 per cent, chlorine, and in practice, 1,100 Ib. 
 of Mn0 2 are necessary for this production, or rather that 
 amount of mud containing 1,100 Ib. Mn0 2 . The lime 
 used, is generally prepared like that used for making 
 bleaching powder (see chapter xvii.), and its consump- 
 tion averages 14 cwt. per ton of bleach. By this process 
 1 ton of bleach is made, using 2,832 Ib. of hydrochloric 
 acid (HC1), generated by the decomposition of 47*5 cwt. 
 of salt, viz., a quantity which theoretically yields 3,3341b. 
 HC1. There is, therefore, a loss of acid of 15 per cent. 
 The loss of manganese varies from 4 to 10 per cent. 
 The whole of the lime is lost, and two-thirds of the total 
 chlorine (in combination with calcium) contained in the 
 acid used. 
 
 The following table is employed in works where 
 Weldon's process is in use, for the estimation of the 
 ' base/ that is the CaO and MnO in the mud. 
 
 ' As the number of grains of ferrous sulphate (FeS0 4 
 7H 2 0) peroxidised by the Mn0 2 in a given volume of 
 manganite mud, is to the number of grains of oxalic acid 
 (C 2 H 2 4 2H 2 0) decomposed and neutralised by the same 
 volume of the mud ; so is 100 to a figure in column A 
 against which in column B is the per cent, of bases : 
 
DETERMINATION OF 'BASE* IN MANGANESE MUD. 203 
 
 A 
 
 B 
 
 69-00 
 
 65-75 
 
 62-50 
 
 59-25 
 
 1-044 
 
 901 
 
 758 
 
 615 
 
 68-75 
 
 65-50 
 
 62-25 
 
 59-00 
 
 1-033 
 
 890 
 
 747 
 
 604 
 
 68-50 
 
 65-25 
 
 62-00 
 
 58-75 
 
 1-022 
 
 879 
 
 736 
 
 593 
 
 68-25 
 
 65-00 
 
 61-75 
 
 58-50 
 
 1-011 
 
 868 
 
 725 
 
 582 
 
 68-00 
 
 64-75 
 
 61-50 
 
 58-25 
 
 1-000 
 
 857 
 
 714 
 
 571 
 
 67-75 
 
 64-50 
 
 61-25 
 
 58-00 
 
 989 
 
 846 
 
 703 
 
 560 
 
 67-50 
 
 64-25 
 
 61-00 
 
 57-75 
 
 978 
 
 835 
 
 692 
 
 549 
 
 67-25 
 
 64-00 
 
 60-75 
 
 57-50 
 
 '967 
 
 824 
 
 681 
 
 538 
 
 67-00 
 
 63-75 
 
 60-50 
 
 57-25 
 
 956 
 
 813 
 
 670 
 
 527 
 
 66-75 . 
 
 63-50 
 
 60-25 
 
 57-00 
 
 945 
 
 802 
 
 659 
 
 516 
 
 66-50 
 
 63-25 
 
 60-00 
 
 56-75 
 
 934 
 
 791 
 
 648 
 
 505 
 
 66-25 
 
 63-00 
 
 59-75 
 
 56.50 
 
 923 
 
 780 
 
 637 
 
 494 
 
 66-00 
 
 62-75 
 
 59-50 
 
 56-25 
 
 912 
 
 769 
 
 626 
 
 483 
 
 It is of extreme importance to keep down the amount 
 of base in the mud as low as possible, because lime and 
 protoxide of manganese have, of course, no power to gene- 
 rate chlorine from hydrochloric acid, but simply dissolve 
 in it, thus 
 
 CaO or MnO + 2HCl=H 2 + CaCl 2 or MnCl 2 . 
 
 To effect this desideratum it is essential that no more 
 lime should be used in the oxidiser than is absolutely 
 required, because a great excess of lime causes the 
 formation of compounds which do not admit readily of 
 peroxidation. In fact, in many works, a little chloride 
 of manganese solution is now added after the full comple- 
 ment of lime has been charged into the oxidiser. 
 
 In relation to Weldon's process, a provisional speci- 
 fication was taken out by Mr. Valentin, of the School of 
 Science. He discovered that ferricyanide of potassium 
 acts as a carrier of oxygen to protoxide of manganese, 
 and he proposed to apply this discovery in industry. For 
 this purpose the still liquors, after neutralisation with 
 lime, are precipitated by a chemical equivalent of lime, 
 
204 THE ALKALI TRADE. 
 
 and instead of adding more lime, as is done in Weldon's 
 process, a solution of potassic ferricyanide is added, and 
 air blown through, whereby the protoxide becomes 
 peroxide of manganese, and in much less time than in 
 Weldon's process. 
 
 It is probable that the influence of the ferricyanide 
 consists in yielding up its oxygen to the mud, being at 
 the same time reduced to ferrocyanide, and this being re- 
 converted into ferricyanide, these reactions are continually 
 repeated until the whole of the manganese is peroxidised. 
 To effect this, it was found that about 10 Ib. of the ferro- 
 cyanide were requisite per ton of manganese mud, and 
 Mr. Valentin calculated that this form of process would 
 yield ' bleach ' at about 105. per ton cheaper than Wel- 
 don's process. Unfortunately, a difficulty was encoun- 
 tered. It was necessary that the ferrocyanide should be 
 recovered for two reasons, viz., on account of its cost, and 
 to prevent cyanogen compounds entering the chamber 
 with the chlorine ; and to recover the ferricyanide it was 
 found necessary to filter the mud, an operation which 
 on so large a scale proved to be impracticable. 
 
 This process of Mr. Weldon's is fraught with interest 
 apart from its industrial value. We have seen that its 
 inventor claims to have proved the formation of mauga- 
 nites that is, bodies which may be viewed as salts in 
 which the base is calcium or manganese protoxide, and 
 the acid radical manganic peroxide ; thus, CaOMn0 2 and 
 MnOMn0 2 ; and possibly also (CaO, MnO) (Mn0 2 ) 2 . 
 
 The great interest of the process attaches to the high 
 state of oxidation attained by the manganese. If air, or 
 even oxygen, be blown through protoxide of manganese 
 suspended in solution, only the sesquioxide is formed 
 
VALENTIN'S IMPROVEMENTS. 205 
 
 (Mn 2 3 ) ; but, as before said, if this oxidation be effected 
 in the presence of ferri cyanide of potassium, peroxide of 
 manganese (Mn0 2 ) is produced. Mr. Valentin explains 
 this as a process in which the ferricyanide acts as a carrier 
 of oxygen, and it is instructive to compare this reaction 
 with other similar ones known to chemical science. 
 
 Suboxide of copper, or cuprous oxide Cu 2 0, is a red 
 body, and tolerably stable in the pure state at normal 
 temperatures. When dry, it passes into a higher state 
 of oxidation if heated to a temperature considerably 
 above 100 C. If placed in water and submitted to a 
 current of air or oxygen, it is unaffected, as the author 
 has shown ; but the presence of a small quantity of a 
 caustic alkali under these conditions induces a peroxi- 
 dation even in the cold, and more rapidly in the hot ; 
 and in this way the red lower oxide is transformed into 
 the black oxide, CuO. Here, therefore, the alkali acts as 
 a carrier of oxygen, and this hypothesis derives consider- 
 able support from Harcourt's discovery of higher oxides 
 of potassium and sodium than those which form the base 
 of ordinary caustic alkaline solutions. It is, therefore, to 
 be supposed that in the above reaction the oxide of 
 sodium or potassium is, for the time being, continually 
 peroxidised and reduced, yielding the oxygen thus carried 
 to the oxide of copper. 
 
 There are many such ' continuous actions,' as they 
 are called, in chemistry. As we have seen in a previous 
 chapter, sulphuric acid is manufactured by a process in 
 which an oxide of nitrogen acts as a carrier of oxygen to 
 sulphurous anhydride, and there is practically attempted, 
 and partially realised, what theoretically takes place, viz., 
 the transformation of an infinitely large amount of sul- 
 
206 THE ALKALI TRADE. 
 
 phurous anhydride into sulphuric acid, by means of an 
 indefinitely small quantity of nitric acid. 
 
 The process by which ordinary ether is made, is 
 another similar and striking instance of this class of 
 reactions, and may be expressed as the conversion of an 
 infinitely large amount of alcohol into ether, by means 
 of an indefinitely small quantity of sulphuric acid. Thus 
 the process is supposed to take place in two distinct phases, 
 and that this truly represents what actually occurs, has 
 become almost matter of certainty, through some ela- 
 borate researches of Williamson. 
 
 (1) H 2 S0 4 + C 2 H 5 HO=C 2 H 5 HS0 4 
 
 (2) C 2 H 5 HS0 4 + C 2 H 5 HO=(C 2 H 6 ) 2 + H 2 S0 4 . 
 
 In the next chapter we shall consider an improved 
 form of Mr. Weldon's process as here described. 
 
WELDON'S MAGNESIA CHLORINE PROCESS. 207 
 
 CHAPTEK XV. 
 WELDON'S MAGNESIA CHLORINE PROCESS (b). 
 
 THE success attending Weldon's process for the manu- 
 facture of chlorine gave an impetus to researches in 
 chemical industry, and one result was the perfection of 
 another method for making chlorine devised by Mr. 
 Deacon of Widnes. This process we shall describe in the 
 next chapter. 
 
 Here we shall record those efforts made by Mr. Wei- 
 don to perfect his own process by the substitution of 
 magnesia (to be recovered) in the place of lime. 
 
 These experiments must be regarded as highly suc- 
 cessful, and showed that the process admitted of many 
 modifications, none of which, however, have been adopted 
 by manufacturers for one reason, viz., because they were 
 satisfied with the results obtainable with the old form of 
 the process. 
 
 Should an increased demand for bleaching powder 
 arise, it is not unlikely that the process now to be described 
 will come into use. 
 
 The process commences by neutralising the acid 
 liquor from the stills, formed by the action of hydro- 
 chloric acid on native manganese, with Greek stone or 
 very nearly pure magnesite (carbonate of magnesium). 
 Or, if it be desirable, the Greek stone may be first cal- 
 cined and the light, easily- dissolved magnesia powder, so 
 
208 THE ALKALI TRADE. 
 
 made, used in its stead. This operation is performed in 
 a well of cast-iron, or the liquor may be neutralised 
 in the stills. 
 
 The mixed chlorides of manganese and magnesium 
 liquor, obtained as described, is pumped into the settlers, 
 where any peroxide of iron, alumina and gypsum depo- 
 sit. This gypsum is derived from the sulphuric acid 
 contained in commercial hydrochloric acid. From the 
 settlers-the* liquor is run into an iron .pot, or pan, where it- 
 is evaporated until it attains a state of concentration, re- 
 gistering a temperature of about 320 Fahr. At this 
 stage the evolution of hydrochloric acid gas commences, 
 from the decomposition of the magnesic chloride by water. 
 By opening a screw plug (of metal) it is now run into a 
 muffle furnace, consisting of two divisions, which commu- 
 nicate with each other by means of an iron door worked 
 by a pulley from without. 
 
 In one of these compartments the evaporation to dry- 
 ness is completed, and is accompanied by the evolution of 
 much hydrochloric acid, plus a little chlorine. The re- 
 sidue, which, by stirring constantly at this stage, is broken 
 up into thin cakes, is then transferred by means of a rake 
 into the second compartment, where it is heated with 
 access of air. 
 
 Here the heat requires careful regulation, for if the 
 temperature rises too high, fusion ensues, and thus the 
 porosity of the mass is lost and oxidation impeded. The 
 best heat is one designated ' blood-red,' and if this be 
 attained and kept, the oxidation proceeds very regularly 
 till the end. This tendency to fuse on the part of the 
 mixture is due to the magnesic chloride, and therefore it 
 is greater in the first place than afterwards, when it is 
 
MANGANITE OF MAGNESIUM PROCESS. 209 
 
 partially decomposed, as magnesia exhibits no such dis- 
 position. In other words, the furnace may be brightly 
 red hot in the first compartment, because the temperature 
 is greatly reduced by the evaporation which there takes 
 place. As the mixture passes into the second compart- 
 ment of the furnace, it consists of manganese chloride, 
 together with magnesic chloride and magnesia, hence it 
 is at this stage, that the temperature must be carefully 
 watched ; but as the decomposition proceeds, the magnesic 
 chloride becomes less and less in quantity, and therefore 
 the temperature may be allowed to increase to some 
 extent with the decomposition. At the same time that 
 the magnesium chloride undergoes decomposition, so also 
 does the manganic chloride, and there is thus obtained 
 protoxide of manganese, which absorbs oxygen from the 
 air which is admitted, and becomes peroxide. This latter 
 body appears to combine with the magnesia under these 
 circumstances, and forms what Mr. Weldon has termed 
 manganite of magnesium (MgMn0 3 ), which when properly 
 made, is a dense, black, finely divided powder. It should 
 be understood, however, that all the manganese is not 
 peroxidised, in short, that there remains a certain portion 
 as protoxide, and this, with the magnesia, constitutes 
 what is termed the ' base/ that is, it furnishes with hydro- 
 chloric acid no free chlorine. It is only the manganese 
 which exists as peroxide, that is capable of liberating 
 chlorine in the stills. Now, so long as water is present 
 in the furnace, hydrochloric acid is evolved, and as the 
 main evaporation takes place in the first division of the 
 furnace, it is chiefly hydrochloric acid which is there 
 generated. In the second division it is chiefly chlorine 
 
210 THE ALKALI TRADE. 
 
 which is evolved, but it is of course mixed with some 
 hydrochloric acid. 
 
 <MgCl 2 + H 2 0=MgO + 2HC1 
 < MnCl 2 + H 2 0=MnO + 2HC1 
 
 2MnO -MMgO + Q=MgMnO 3 . 
 
 These equations probably represent the reactions in the 
 order in which they occur in the furnace. It is, indeed, 
 doubtful whether much manganese chloride is decomposed 
 by the water, so long as there remains any chloride of 
 magnesium, as this latter body is far more readily decom- 
 \ posable. Any water which may be left, would then 
 attack the chloride of manganese, and finally, the mix- 
 ture of oxide of manganese and magnesia absorbs oxygen 
 to form the compound manganite of magnesium. Of 
 course, to a certain extent, all these reactions take place 
 at the same time, but not in the same measure. 
 
 Portions of the charge may be withdrawn from the 
 furnace from time to time, and tested for the amount of 
 manganic peroxide, and when this amount ceases to in- 
 crease, the operation is concluded./ The charge is now 
 withdrawn, and is placed in the stills when cold, there 
 to decompose a renewed quantity of hydrochloric acid, 
 giving undiluted chlorine ; the liquor so obtained is 
 perfectly neutral, or may be made so by addition of a 
 little magnesia, and is then ready to pass once more 
 through the cycle of operations already sketched : so 
 the process is repeated ad infinitum, without being at- 
 tended with any waste product whatever. 
 
 The manganite of magnesium may be charged into 
 the stills in one of two or three ways, namely, either in 
 the state in which it conies from the furnace, or in the 
 form of a sludge made by grinding it in a mill with 
 
TREATMENT OF DILUTE CHLOEINE GAS. 2-11 
 
 water, or it may be added gradually through a valve so 
 constructed that while it admits the charge, it does not 
 allow of the escape of the chlorine. In any case it is 
 always charged in slight excess, so that there results a 
 practically neutral still liquor. This liquor is allowed to 
 settle somewhat before drawing off, so that any excess of 
 the furnace-product left undecomposed is not lost, but 
 remains in the still for a subsequent operation. 
 
 Now, we have seen that of all the chlorine formed in 
 this process, that generated in the still alone is undiluted, 
 whilst that evolved in the furnace is mixed with much 
 hydrochloric acid and nitrogen from the air, together 
 with that excess of air that may have been used in the 
 process of fire oxidation (or pyr 'oxidation). The mixed 
 gases are drawn by chimney draught, through the ' coke 
 scrubbers ' in the ordinary way (see Salt-cake chapter), 
 by which means the hydrochloric acid is washed out, 
 thus giving a product strong enough to serve the purpose 
 of reacting upon fresh manganese in the still. Evidently, 
 several courses now present themselves for dealing with 
 the dilute chlorine. In the first case, the strong chlorine 
 can be used at once in the old chambers, or it can be 
 mixed with the dilute gas, producing a gas of sufficient 
 strength to form ' bleach.' On the other hand, the weak 
 chlorine admits of a process which effectually removes 
 the air and the nitrogen. .This was carried out on a 
 manufacturing scale in St. Helens, by introducing the 
 gases into leaden towers from below, where they, in their 
 ascent, meet with a shower of milk of lime, which unites 
 with the chlorine, forming at first ordinary ' bleach 
 liquor,' but which, on the absorption of a further amount 
 
 p 2 
 
212 THE ALKALI TRADE. 
 
 of chlorine, produces a liquor containing only chloride of 
 calcium and free hypochlorous acid, thus : 
 
 CaCl 2 + CaCl 2 2 + 2H <2 + 2Cl 2 =2Ca01 2 + 4HC10. 
 
 Assuming that such a liquor could be constantly ob- 
 tained of this composition, it could be utilised in two or 
 three ways. First, it admits of being pumped direct into 
 the ' octagons/ where it is treated hot with chloride of 
 potassium, to make chlorate of potassium ; or it may be 
 placed in the still and treated with hydrochloric acid, 
 when the following reaction occurs : 
 
 4HC10 + 4HC1=4H 2 + 4C1 2 . 
 
 That is to say, the hypochlorous and hydrochloric acids 
 mutually react, giving rise to free chlorine and water. 
 The chloride of calcium takes no part in the reaction, 
 and is lost. But here is the danger of the process. It is 
 a difficult thing to keep down the temperature in the 
 towers where the chlorine is absorbed by lime milk, and 
 when the temperature rises above a certain height, chlo- 
 rate of calcium is formed, and the presence of this body 
 in the liquor might, if used in the stills, give rise to very 
 serious accidents on account of the explosive nature of 
 the oxides of chlorine there liberated in such a case. 
 Moreover, the action of hydrochloric acid upon hypo- 
 chlorous acid is terribly violent, and attended with 
 danger. This danger is obviated, however, in great mea- 
 sure, by running the hypochlorous acid solution in a thin 
 stream into the hydrochloric acid contained in the still. 
 We have in chapter xiii. referred to the isolation of 
 calcic hypochlorite, and shown that, in the future, manu- 
 facturers may possibly seek to make this body instead of 
 bleaching-powder. This could only be done, so far as 
 
PURE CALCIC HYPOCHLORITE. 213 
 
 we know, in one way, and that at present a difficult one. 
 If it could be successfully accomplished, it would at once 
 employ the liquors of which we have been treating above. 
 Thus, in the towers, where the milk of lime is exposed to 
 the chlorine, we should have to stop at that stage where 
 bleach liquor results, and avoid the formation of hy- 
 pochlorous acid. The reaction in that case would be as 
 follows : 
 
 2CaH 2 O 2 + 2Cl 2 =CaCl 2 + GaCl 2 O 2 + 2H 2 0. 
 
 This liquor, as the author of this work has shown, gives, 
 on evaporation in vacuo over sulphuric acid, a crystalli- 
 sation of pure hypochlorite of calcium, leaving the very 
 soluble chloride of calcium in solution. Now, if such an 
 evaporation could be conducted on a manufacturing scale, 
 so, surely, might this process assume the extent of a trade. 
 Unfortunately, heat cannot be employed to concentrate 
 the liquor, for in that case, as we have seen, calcic chlo- 
 rate results. 
 
 Leaving this part of our subject, Mr. Weldon claims 
 to be able to produce, by the manganite of magnesium 
 chlorine process above sketched, 1 ton of bleach per 
 16 cwt. of salt used (to generate the hydrochloric acid). 
 ' This is about four times the average yield,' says Mr. 
 Weldon, in a manifesto of February 6, 1872, 'obtained 
 at present.' 
 
 Further, by varying the proportions of the chlorides of 
 manganese and of magnesium, it can be so arranged that 
 ' the proportion of the strong chlorine generated in the 
 still, to that of the weak chlorine produced in the furnace, 
 maybe anything between one to one and one to. four, 
 at will.' 
 
 JHI7SRSITY; 
 
214 THE ALKALI TRADE. 
 
 The process is continuous, and requires, from its 
 simple character, but little skilled labour. No machinery 
 (excepting liquor pumps) is involved ; the plant required 
 is comparatively low in cost, compared either with the 
 Weldon process in general use, or Deacon's process, and 
 Mr. Weldon claims for it the production of ' bleach ' at a 
 less cost per ton than by any other process, even throw- 
 ing the whole cost on the strong chlorine only. These, 
 however, are matters which, in event of the process being 
 adopted, would require a more extended experience to 
 decide with certainty. 
 
 One word more may conveniently be said here re- 
 garding the furnace product. Its composition, of course, 
 varies with the nature of the liquors which furnish it, 
 that is to say, it depends upon the relation existing be- 
 tween the chlorides of manganese and magnesium em- 
 ployed ; and as the magnesia does not serve to generate 
 chlorine, but only to neutralise the ' still ' liquors, and to 
 assist by its presence, in the oxidation of the manganese 
 protoxide, it becomes desirable to use the minimum 
 amount allowable. 
 
 Theoretically, the best proportions are those of one 
 to one, because, in the compound manganite, this is the 
 relation in which the magnesium stands to the manga- 
 nese (MgMn0 3 ). Had the furnace-product this exact 
 constitution, it would have the value, in terms of oxygen, 
 of a native ore containing 68 -3 per cent. Mn0 2 ; but pro- 
 bably, owing to the excess of magnesia, and manganese 
 existing as protoxide, the percentage of manganic dioxide 
 in the product would practically be about 40 to 50 per 
 cent. Finally, it should be stated that Mr. Weldon has 
 proposed the plans of dealing with the dilute chlorine, 
 
COMPARISON OP CHLORINE PROCESSES. 215 
 
 not only in regard to his own process, but as equally 
 applicable to chlorine furnished in a dilute state by any 
 other process, such as Deacon's, to be hereafter studied. 
 
 As a matter of history, it should be remarked that 
 several plants were erected in Lancashire for working 
 this improved form of Weldon's process, but they were 
 ultimately abandoned. At the time, bleaching powder 
 had undergone a depreciation in value, and, in fact, the 
 production was in excess of the demand. Meanwhile 
 Deacon's process was being condemned by many manufac- 
 turers as much less successful than Weldon's old process. 
 In the face of these facts, producers did not feel justified 
 in adopting the new form of a process which in its ori- 
 ginal modification gives such excellent results. 
 
 We have described, however, the improvements some- 
 what fully, from the conviction of their possible impor- 
 tance in the future. This conviction is strengthened by 
 the writer's personal acquaintance with the process and 
 its working results. Its great importance rests upon the 
 fact that the loss of lime experienced in Weldon's process 
 now in general use, is obviated by these improvements, 
 while if magnesia be substituted in the towers for 
 absorbing the dilute chlorine, there is virtually no loss 
 of hydrochloric acid experienced, for side by side with 
 hypochlorous acid, magnesic chloride is produced, and 
 from this the hydrochloric acid is regenerated by simple 
 evaporation and ignition. 
 
 At the same time, the element of cost enters largely 
 into all these matters, and an extended experience could 
 alone decide their feasibility in practice. 
 
216 THE ALKALI TRADE. 
 
 CHAPTER XVI. 
 DEACON'S AND OTHER CHLORINE PROCESSES. 
 
 THE process bearing Mr. Deacon's name was first brought 
 before the public, at the British Association meeting of 
 1870. It excited at that time much attention, and indeed, 
 for some period it was doubtful whether it would not 
 rival or even displace the Weldon process. Further 
 experience, however, discovered difficulties in the practi- 
 cal working of this beautiful method, which exercise a 
 deteriorating influence on its value, and lessen its applica- 
 bility. Although several plants have been erected in 
 connection with this mode of manufacturing chlorine, 
 most of them have been since abandoned, and at the 
 present time, as we have seen, most of the chlorine is 
 manufactured according to the process of Mr. Weldon. 
 
 Mr. Deacon laboured hard to perfect his method, even 
 up to the time of his lamented death, and during his 
 investigation many important facts were discovered. 
 These he communicated in the form of a lecture to the 
 Chemical Society of London, on June 20, 1872. The 
 process itself consists in passing ' roaster ' or hydrochloric 
 acid gas along with air, over sulphate of copper super- 
 ficially dried upon some refractory substance, such as 
 brick. For the time being, the sulphate of copper 
 appears to be transformed into chloride of copper ; and, 
 in fact, it would seem that the process may be viewed as 
 
DEACON'S CHLORINE PROCESS. 217 
 
 a combination of two reactions, which occur simulta- 
 neously : 
 
 CuO + 2HCl=CuCl 2 =H 2 O. 
 
 These equations may at least be considered to re- 
 present the extreme result attainable. It has long been 
 known that chlorine is formed when hydrochloric acid 
 and air are heated strongly together, and in a previous 
 chapter we have observed that the reactions represented 
 by the above two equations were also known to chemists. 
 
 Mr. Deacon's process combines these two, and he 
 further employs sulphate of copper, which allows the 
 formation of chlorine to take place at much lower tem- 
 perature than otherwise. Theoretically, the action itself 
 should generate enough heat for the purpose, but practi- 
 cally, owing to losses by radiation, etc., a considerable 
 amount of fuel is required to aid the process. 
 
 Originally, common red brick was employed for the 
 purpose of exposing a surface of the sulphate of copper to 
 the mixed gases, and at the present time, at one place, 
 to our knowledge, firebrick broken up into pieces of the 
 size of a walnut is employed. But Mr. Deacon preferred, 
 we believe, to employ clay balls or marbles, and recently, 
 we are informed, he had used a mixed solution of 
 the sulphates of copper and of sodium. The sulphate of 
 sodium appeared not only to increase the activity, but, 
 moreover, increased the resistance offered to permanent 
 decomposition of the cupric sulphate. Mr. Deacon has 
 shown that the action is essentially a surface one, and ' it 
 would appear that there is a certain comparatively small 
 range of temperature, between the critical limits of which, 
 the percentage of hydrochloric acid decomposed, varies 
 
218 THE ALKALI TRADE. 
 
 greatly, and that this is not the same for the^chloride as 
 for the sulphate (of copper), being higher for sulphate.' 
 
 He has further concluded that, 'other conditions 
 remaining the same, the percentage of hydrochloric acid 
 decomposed varies with the square root of the propor- 
 tionate volume of oxygen to hydrochloric acid,' and ' that 
 the chloride of copper formed bears no definite proportion 
 to the amount of chlorine produced.' In the absence of 
 clay, and below a certain temperature, chlorine is freely 
 formed, without conversion of the sulphate ; but in the 
 presence of clay the sulphate becomes transformed into 
 chloride, and in any case, above a certain temperature 
 (about 800 Fahr.), chloride is permanently formed, and 
 volatilises. The bricks or marbles are dipped in sulphate 
 of copper, dried, and placed in the decomposer, which is 
 constructed of iron and encased in brickwork. Under 
 these circumstances they are maintained at a temperature 
 of 700 to 750 Fahr. (below 400 Fahr. the reaction does 
 not occur). 
 
 Taking the hydrochloric acid gas as it is furnished in 
 the salt-cake apparatus, described in a preceding chapter, 
 it is found to contain enough air to insure the decom- 
 position of the hydrochloric acid gas, although it is in the 
 power of the manufacturer to vary the proportions within 
 limits, at will. The mixed gases are drawn over the 
 marbles by mechanical suction, or chimney draught. 
 
 Latterly, Mr. Deacon had improved his decomposer, 
 because . it was found that, after a few months' working, 
 the brick would become inactive. In this improved form 
 of apparatus, he seeks to remedy this defect, by making 
 arrangements through which the inactive, worked-out 
 firebrick can be withdrawn through a trap, and a fresh 
 
THE NATURE OF DEACON'S PROCESS. 219 
 
 supply added once a week from the top, from which it 
 descends by its own gravity to the copper-soaked marbles. 
 All this can be done without stopping work, and better 
 results are expected from it than are secured with the 
 ordinary form of decomposer. 
 
 Previous to this improvement, difficulties had been 
 encountered in this direction. It had been observed that 
 after a certain period of regular working, the catalytic 
 agent lost its power in some degree, and this appeared 
 to be at least partly due to the volatilisation of some 
 chloride of copper, and to its consequent localisation in 
 specific places, or the sulphate of copper gradually worked 
 itself into the interior of the brick, leaving the surfaces 
 deprived of part of its activity. To remedy these evils, 
 Mr. Deacon would allow the decomposer to cool down 
 from time to time to about 220 Fahr. and then pass 
 in steam. This dissolved the copper sulphate, and the 
 solution thus formed was in this way once more gradually 
 distributed over the surface of the brick or other matter. 
 It is difficult to speak in a precise manner about these 
 obstacles and their remedies, for the real chemical re- 
 actions occurring are still, in great measure, matters of 
 speculation. Mr. Deacon appeared to believe that the 
 process, when properly conducted, did not depend upon 
 the transformation of the sulphate into chloride of copper, 
 but viewed the production of the chlorine as resulting from 
 a mere decomposition -of hydrochloric acid by oxygen, 
 brought about by contact or collision of the gaseous mole- 
 cules with the sulphate of copper. Thus he regarded it in 
 some way to be a mechanical action only ; but this is 
 scarcely warrantable, when it is considered that contact 
 with some sorts of substances is not so effectual as is the 
 
220 THE ALKALI TRADE. 
 
 case with other sorts. The fact that there is a difference 
 of power at all in what is called the catalytic substance, 
 implies a difference of process. 
 
 Thus chromic oxide has the same kind of power as 
 the sulphate of copper in transforming hydrochloric acid 
 and oxygen into chlorine and water, and, indeed, its use 
 was patented by a Belgian as an improvement on the 
 latter substance. But while it has the advantage of non- 
 volatility, its use is open to the same objection that is true 
 of any form of the process, viz., the production of dilute 
 chlorine. 
 
 Before passing on to this subject, however, we may 
 add that among other substances which act like sulphate 
 of copper and chromic oxide, are platinum black or 
 spongy platinum, manganese compounds, etc. Platinum 
 is best used by soaking brick, or asbestos in a solution 
 of its chloride ; if then the substance be subjected to a 
 red heat, the platinic compound is decomposed, leaving 
 a film of the metal over the surface. Any porous sub- 
 stance has the catalytic power, only in a less degree than 
 when supplemented by some such agent as sulphate of 
 copper. 
 
 To return to the study of the chlorine produced by 
 this process. It is associated with all the nitrogen of the 
 air, and any excess of air that may have been used, and 
 for a long time it was thought that such dilute chlorine 
 could not be used for making strong bleaching powder, 
 that is, it would present difficulty in its absorption by 
 lime. Nevertheless, by careful regulation of the amount 
 of air used, a gas can be obtained which will produce 
 4 bleach ' of full strength, under conditions to be hereafter 
 described. 
 
SPECIAL BLEACHING-POWDER CHAMBERS. 221 
 
 A perfect decomposition of the hydrochloric acid is 
 never effected, and hence it becomes necessary to wash 
 out the hydrochloric acid attached to the chlorine en 
 route for the chambers. Hence, in any case, Weldon's 
 or some other process would have to be employed to 
 work up this condensed hydrochloric acid. Of course 
 it could be used by boiling it to generate fresh gas for 
 the ' decomposer ' ; but this would entail a large consump- 
 tion of fuel. After freeing the chlorine from hydrochloric 
 acid, it has to be dried by passing through a tower, 
 wherein it is exposed to sulphuric acid of specific gravity 
 1-6, and in some works it then passes on to another tower 
 packed with fused chloride of calcium. Here the drying 
 is completed, and the gas is then ready for chamber con- 
 sumption. But for this purpose the ordinary form of 
 chamber, the consideration of which matter we reserve 
 for our next chapter, cannot be employed. In this place 
 we shall briefly describe the form of chamber used in the 
 Deacon process only. 
 
 The stronger and purer the chlorine, the more readily 
 is it absorbed by lime, and vice versa. When dealing, 
 therefore, with such dilute gas as is obtained in the pro- 
 cess under description, there must be presented to it a 
 larger surface of absorbing material, and this is done by 
 spreading upon a series of shelves made of slate, lime 
 to the depth only of about f of an inch. The lime is 
 charged into the chambers from the top through a hopper, 
 and is then spread upon the shelves by means of a rake 
 having a gauge off of an inch. These shelves are 6 inches 
 one below the other, and are so constructed that the fresh 
 chlorine first passes over that powder, which is already 
 most nearly saturated, and thenre to the less chlorinated 
 
222 THE ALKALI TEADE. 
 
 lime. In this way good bleach containing 37 or 38 per 
 cent, chlorine may be readily prepared. 
 
 Altogether, the Deacon process, so far, cannot be said 
 to have worked so well as was expected, and no plant yet 
 constructed, has been able to produce that amount of 
 bleaching powder which it was calculated and destined 
 to give. 
 
 The various difficulties encountered in the process of 
 working may be thus enumerated : 
 
 1. The roaster gas is liable to contain carbonic acid 
 gas, which presents an obstacle in the production of good 
 bleach, forming as it does carbonate. 
 
 2. The plant being largely constructed of iron and 
 exposed to high and inevitably varying temperatures, the 
 joints are liable to give way, and admit the products of 
 combustion from the furnace outside. 
 
 3. The copper is apt to volatilise as chloride, which 
 condenses in the cooler part of the decomposer, impeding 
 the draught, and involving stoppage for cleaning ; while 
 the marble, under such circumstances, requires periodi- 
 cally redressing. 
 
 We have endeavoured to sketch this process fairly 
 and truthfully, and if we appear to have laid special stress 
 upon the difficulties inherent in it, we feel justified by the 
 importance of the subject. Nevertheless, the circum- 
 stances and conditions under which this process can 
 attain commercial success, may yet be discovered, and 
 thus reward the indefatigable exertions already made to 
 perfect it, by Mr. Deacon and his chemist, Dr. Hurter. 
 
 Illustrative of these difficulties, it may be stated that 
 a new anemometer, for measuring the speeds of the gases 
 to the decomposer, had to be invented, and also new 
 
A NEW CHLORINE PROCESS. 223 
 
 forms of pyrometers for indicating their temperatures. 
 Further, when it is considered that a manufacturer, 
 making 40 tons of sulphate of sodium daily, in order to 
 use ah 1 his hydrochloric acid as generated, would have to 
 deal with about 1,100,000 cubic feet of gases, the means 
 whereby they have been enabled to partly accomplish 
 this, reflect exceedingly well on those who have devised 
 them. 
 
 In passing from this study, there yet remains one 
 other process to be described before we proceed to some 
 further considerations regarding the production of bleach- 
 ing powder. The process we refer to, is the subject of 
 a patent by Messrs. James Hargreaves and Thomas 
 Eobinson, and has been proposed in reference to the 
 manufacture of hydrochloric acid and chlorine. 
 
 One part of potassic or sodic chloride is mixed with 
 two to three parts of oxide of chromium, and with or 
 without magnesium or manganese as oxide, or in the 
 form of a salt, to assist in the production of chromic 
 acid. The mixture is moulded into bricks with water, 
 and then dried. These are then exposed to a current of 
 air, at a temperature which may be expressed as ' red 
 heat,' but below fusion, in a series of furnaces or other 
 chambers. In this way chlorine is generated, and the 
 sodium or potassium converted into chromate. If hydro- 
 chloric acid be the desired product, along with the 
 current of air, is used one of steam also. In both in- 
 stances, if desirable, the air may first be made red hot 
 by use of the air-heating apparatus of the Messrs. Siemens. 
 The equations illustrating the decompositions may be thus 
 expressed : 
 
 (1) 2 
 
 (2) 2NaCl + Cr 2 O 3 + H,0 + 4 = 2NaCiO 4 + 2HC1. 
 
224 THE ALKALI TRADE. 
 
 CHAPTEE XVII. 
 
 MANUFACTURE OF BLEACHING POWDER, BLEACHING LIQUOR, 
 CHLORATE OF POTASSIUM, AND EPSOM SALTS. 
 
 BLEACHING POWDER is produced commercially by the 
 action of chlorine prepared by any of the afore-described 
 processes upon slaked lime. 
 
 The chlorine gas is first dried by passage through 
 small leaden or other purifiers, packed with coke or 
 flints, kept well supplied with strong sulphuric acid. In 
 many works the chlorine is washed by passing it through 
 water before drying. This is done in order to prevent 
 the occurrence of traces of manganese in the bleaching 
 powder for it is asserted that peroxide of manganese, 
 even when present in very minute amounts, greatly 
 facilitates the spontaneous decomposition of the product, 
 with the evolution of oxygen. This is a matter, how- 
 ever, yet requiring investigation. The choice of the 
 lime used is of much importance, many kinds containing 
 traces of ferric or manganic oxide ; and such substances 
 give to the ' bleach ' the induced liability to decom- 
 position already referred to. Such lime is to be identified 
 by its yellow colour. Irish and French limestones furnish, 
 by a process of calcination, most of the lime used in this 
 country, as they give a ' heavy ' lime, which is the best 
 sort to employ. Large quantities of limestone are also 
 obtained from Buxton. 
 
BLEACHING POWDER CHAMBERS. 225 
 
 Having obtained the lime in a well-burnt state, it has 
 next to be carefully slaked ; if too much water be em- 
 ployed in the operation, the product agglomerates ; and 
 if too little water be used, the product absorbs chlorine 
 imperfectly. After slaking, it is sifted from the ' yelks ' 
 that is, unburned carbonate, pebbles and impurities 
 and should then contain about 24 per cent, water, in 
 addition to that amount necessary to form hydrate of 
 liine. The vessels, in which the absorption of chlorine by 
 the lime takes place are called ' chambers,' and, as origi- 
 nally constructed, were virtually leaden receivers, in 
 which the lime was stirred from time to time. 
 
 When bleaching powder was first made on the Tyne 
 viz., in 1830, by Losh, Wilson, and Bell wooden 
 chambers covered with pitch were used. Then came 
 chambers of brick, which gave way eventually to others 
 constructed of stone (Yorkshire flagstone), or lead, or 
 both ; some, however, are constructed of iron. Usually, 
 these chambers are built upon the ground, but sometimes 
 they are supported upon a wooden framework. It was 
 usual, moreover, in the past, to place the lime upon a 
 series of shelves to a depth of 5 to 8 centim. (2 to 3 
 inches); these shelves were situated about 6 inches one 
 above the other, and three or four in number were used. 
 Except where chlorine generated by Deacon's process is 
 used, shelves are no longer employed ; and instead thereof, 
 the lime is placed upon the floor to a depth of about six 
 inches. 
 
 Chambers, as now usually constructed, are from 50 
 to 60 feet long, 25 to 80 feet wide, and from 5 to 6 feet 
 high. Most of them are built of lead, in which case they 
 
 Q 
 
226 THE ALKALI TRADE. 
 
 are tarred inside. In any case the bleaching powder is 
 kept from contact with the metal, by having the sides (to 
 the depth of the lime) built of flagstones, on which the 
 leaden or iron body rests. The chambers are provided 
 with doors which are luted on, after the charge of lime 
 has been introduced, and there are also small windows 
 through which may be seen the colour of the gas, a cri- 
 terion, to an experienced workman, of the progress of the 
 absorption. 
 
 The charge of lime varies according to the size of the 
 chamber, 72 cwt. sometimes being employed, and some- 
 times 144 cwt. This having been introduced and the 
 chambers closed, the gas is allowed to enter slowly ; if 
 the operation proceeds too quickly, the temperature rises 
 owing to the combination, and the hypochlorite of calcium 
 which is formed, decomposes into chlorate and chloride. 
 The temperature generally observed is 62 Fahr., although 
 Scheurer-Kestner is of opinion that a temperature of 
 130 Fahr. is not injurious so long as the chlorine does not 
 enter too rapidly. 12 cwt. of good lime yield about 20 
 cwt. of bleaching powder, testing 37 per cent, chlorine ; 
 or, expressed generally, 100 parts of lime should absorb 
 from 64 to 66 parts of chlorine, giving a product testing 
 from 35 to 37 per cent, chlorine. 
 
 Under ordinary conditions, 36 to 48 hours are re- 
 quired to saturate the lime with chlorine ; when com- 
 pleted, the residual chlorine is drawn off by chimney 
 draft or otherwise, into a freshly charged chamber, leav- 
 ing the contents ready for packing. The doors are now 
 unluted, and the ' bleach ' is drawn by wooden rakes 
 towards them, by workmen who protect themselves from 
 the chlorine by holding in their mouths wet rags or 
 
COMPOSITION OF BLEACHING POWDER. 
 
 227 
 
 flannel. The powder is packed firmly in dry wooden 
 casks, and in this state is supplied to the market. 
 
 The following analyses of bleaching powder are by 
 Mr. G. E. Davis, and may be taken as fairly representa- 
 tive : 
 
 ANALYSES OF GOOD SAMPLES. 
 
 Form of Chlorine. 
 
 i 
 
 2 
 
 3 
 
 4 
 
 5 
 
 Total chlorine . 
 Active chlorine . 
 
 36-40 
 35-12 
 
 35-54 
 35-00 
 
 38-62 
 35-50 
 
 37-76 
 35-87 
 
 39-52 
 36-11 
 
 ANALYSES OF BAD SAMPLES. 
 
 Form of Chlorine. 
 
 i 
 
 2 
 
 3 
 
 4 
 
 5 
 
 Total chlorine . 
 Active chlorine. 
 
 33-86 
 30-25 
 
 37-24 
 31-33 
 
 30-52 
 29-46 
 
 30-90 
 
 27-87 
 
 37-51 
 32-30 
 
 The actual value of the powder depends upon its 
 percentage of active chlorine, and the difference be- 
 tween the percentages of total and active chlorine, is that 
 amount in combination as chloride of calcium, which is 
 of course useless for bleaching purposes. The commer- 
 cial bleaching powder has therefore a composition which 
 may be represented by 
 
 Pi 
 
 and contains on the average, 35 to 39 per cent, chlorine, 
 43 to 44 per cent, lime, and 15 to 16 per cent, water, 
 with traces of foreign matters. 
 
 Bleaching powder slowly undergoes spontaneous de- 
 composition, and Mr. J. Pattinson finds that during a 
 summer month the loss of available chlorine may rise as 
 high as 0*86 per cent, on the average ; in a winter month, 
 it loses about 0*26 per cent, on the average. 
 
 Q 2 
 
228 THE ALKALI TRADE. 
 
 In a factory where 350 tons of salt were decomposed 
 weekly, and the strong hydrochloric acid employed in 
 making ' bleach,' the following were the working results, 
 reduced to a standard of 20 cwt. of salt : Common salt, 
 2,240 parts; hydrochloric acid at 28 Tw., 2,753 parts ; 
 manganese at 60 per cent. = 448 parts; producing 416 
 parts of bleach at 39 per cent. (Richardson and Watts). 
 These figures relate to the industry prior to the revolution 
 brought about by the introduction of the Weldon process; 
 so also do the following figures, taken from the same 
 source : Eight large stills in Lancashire supplied five 
 chambers, each still being charged with 7 or 8 cwt. of 
 manganese, and 90 cubic feet of acid at 28 Tw. Each 
 chamber was charged with 43 cwt. lime, taking a week 
 for complete saturation, and giving a production of 64 
 cwt. of 'bleach ' at 35 per cent, strength. 
 
 Using Weldon's process for the generation of the chlo- 
 rine, a ton of ' bleach ' is produced from about 50 to 55 
 cwt. of salt, decomposed. In the Lancashire district, 
 during 1866, it is calculated that 20,000 tons of bleaching 
 powder were produced by twenty manufacturers, while 
 in 1867 the Tyne district yielded 27,000 tons. In 1871, 
 the estimated production of Great Britain and Ireland 
 was 75,000 tons, selling at Wl. per ton, giving, therefore, 
 a total value of three-quarters of a million sterling. At 
 the present time the annual production is about 100,000 
 tons, and over 90 per cent, of this is made, using Wel- 
 don's form of chlorine process ; but this latter calculation 
 does not include about 10,000 tons made by Dunlop's 
 process in Glasgow. In 1799, bleaching powder had a 
 value of 168/. per ton ; its present value is 5/. per ton. 
 Of late years, certain attempts have been made to intro- 
 
SUGGESTED NEW FORMS OF CHAMBERS. 229 
 
 duce an improved form of apparatus or chamber in which 
 the lime absorbs chlorine. We have seen that where 
 Deacon's process is used, it is so contrived that the partly- 
 saturated lime is exposed first to the action of the stronger 
 gas, etc. This idea, we believe, originated with Mr. 
 Gamble, but it is the same idea that pervades the use of 
 the various pieces of apparatus recently devised. That is 
 to say, in all of them it is attempted to bring the gas into 
 more intimate contact with the lime, thus effecting the 
 absorption in a less time than otherwise. This is a result 
 especially desirable to obtain, when a dilute gas is em- 
 ployed, such a gas, in fact, as that furnished in Deacon's 
 process. 
 
 Thus, in some places, revolving cylinders have been 
 employed, and were first adopted by Oberkampf and 
 Widmer in Germany (1816). At home, these cylinders 
 were of sheet iron, 5 feet in diameter, 14 feet long, and 
 coated with cement internally. Each cylinder was charged 
 with 14 cwt. of lime, and made about twelve to fifteen 
 revolutions per hour. The casks in which the powder 
 was packed, were placed beneath the cylinders, and re- 
 ceived their charges after passing through a tammy (sieve). 
 It is conceivable that, using the form of chamber now 
 generally adopted, a simple piece of machinery might be 
 devised, which should act as a haymaking machine, by 
 constantly exposing fresh surfaces of lime to the action of 
 the chlorine. In such case, lime might be used to the 
 depth of several feet. 
 
 Mr. Bramwell, of St. Helens, has patented the use of 
 an apparatus, which consists essentially of an iron cylin- 
 der, provided with pipes for working the gases, and a 
 door for discharging the finished powder. , The cylinder 
 
230 THE ALKALI TRADE. 
 
 is provided with a rod passing through its centre (hori- 
 zontally), and from this rod project a number of arms in 
 various directions. When the cylinder is charged with 
 lime, gas is admitted, and the apparatus within, is caused 
 to work up and down, thus making minute spaces in the 
 lime, into which the gas is supposed to enter, and thus 
 effect the object of the invention. So far as we can learn, 
 however, it has not been tried at all, although if it worked 
 it would have the decided advantage of economising space 
 no mean consideration. 
 
 In another tower-form of chamber, patented by Mr. 
 Leather, of St. Helens, the lime falls in the form of pow- 
 der from a hopper, and is kept in agitation as it falls, the 
 chlorine meeting it from below. We are informed that 
 the experiments made a short time since with this tower- 
 method of making bleach, gave results not at all satis- 
 factory. 
 
 In a third apparatus of Mr. Hargreaves, the lime is 
 placed at the top of a spiral shelf, and is moved gradually 
 downwards by means of a scraper, which, in its action, 
 thus continually exposes fresh surfaces of lime to the 
 chlorine, which enters below and meets the lime in its 
 descent. By the time the lime reaches the bottom, it is 
 supposed to be literally converted into ' bleach,' but, so 
 far as we can learn, no experiments have yet been made 
 with this apparatus. 
 
 In further reference to the manufacture of bleaching 
 powder, the following notes by E. C. Clapham, relative to 
 the trade, as practised in France, are not without interest. 
 The Weldon process is now pretty largely used, but at 
 the time of which we are writing (1874), it had not come 
 into operation. 
 
BLEACH LIQUOR AND POTASSIC CHLORATE. 231 
 
 Instead of using stills, such as we have described in 
 preceding chapters, the French used retorts, made of fire- 
 clay, and not unlike Wolff's bottles in form. A charge 
 consisted of 50 Ib. of ground manganese, with sufficient 
 hydrochloric acid of 30 to 32, and was worked off either 
 by the heat derived from a flue, or by steam. In this 
 way a very complete decomposition of the manganese 
 was effected, the chlorine being conveyed in glass pipes to 
 the chambers. The latter were constructed of stone flags, 
 containing a number of shelves, upon which the lime was 
 spread, and the absorption was not allowed to extend 
 above 32, which is the usual French standard. Many 
 persons claim for a ' bleach ' of this strength more sta- 
 bility than for stronger ones. 
 
 Bleach liquor is still a manufactured product in Great 
 Britain, and, indeed, in 1866, no less than 5,871 tons 
 were produced in the Lancashire district alone. It is 
 made by submitting milk of lime to the action of chlorine, 
 either in towers, as described under ' Weldon's Magnesia 
 Process,' or in a cylinder, enclosed in a wooden box. 
 Mr. Deacon proposed to substitute the carbonate of lime 
 for the hydrate ordinarily employed. In such case a 
 tower is used, packed with chalk or limestone, over which 
 water slowly trickles, as the chlorine ascends from below ; 
 or the carbonate may be ground and made into a milk 
 with water, and the product submitted to the action of 
 the gas in the same kind of apparatus. 
 
 Chlorate of Potassium is also largely made from 
 chlorine, in the manner we shall now proceed to describe. 
 In the form of process generally employed, milk of lime 
 is submitted to the action of chlorine in the hot, and is 
 
232 THE ALKALI TRADE. 
 
 thereby resolved into calcic-chlorate and chloride, 
 thus : 
 
 6CaH 2 2 + 601 a =Ca(C10 8 ) a + 5CaCl 2 + 6H 2 0. 
 
 To the concentrated solution of the mixed salts, potassium 
 chloride is then added, in the proportion of 74*5 parts to 
 each 168 of caustic lime originally used, when the follow- 
 ing reaction takes place : 
 
 Ca(C10 3 ) 2 + 2KC1 = 2KC10 3 + CaCl 2 . 
 
 In practice, however, the milk of lime is submitted to the 
 action of the chlorine in presence of the potassic chloride, 
 until the liquor shows a pink colour, or till free chlorine 
 escapes unabsorbed. The liquors are then allowed to 
 settle in the same vessel, run off, and allowed to 
 crystallise in iron pots or pans. The rough crystals of 
 potassic chlorate, which take about six or seven days to 
 form properly, are powdered and redissolved by hot water 
 in this way. The crystals are placed in bags, and the 
 water is allowed to permeate the contents at such a rate 
 that as the solution drops through the bag into the crys- 
 tallising settlers beneath, it is in a concentrated form. 
 The crystals formed in the settlers are separated from the 
 dust by the motion of an eccentric apparatus, while the 
 mother-liquor is used for re dissolving fresh crops of 
 crystals. Ultimately, the calcic chloride solution is 
 thrown away. 
 
 Owing to the dangerous nature of chlorate of potas- 
 sium, a carbonic acid apparatus is generally kept near at 
 hand, to extinguish any fire that may possibly occur. 
 The ' agitators ' or ' octagons ' in which the chlorate is 
 made, are, as their name implies, eight-sided vessels at 
 times, though generally they are cylindrical in form 
 
MANUFACTURE OF EPSOM SALTS. 233 
 
 The substance is used not only in match-making, but 
 also as an oxidising agent for steam colours on calico, etc. 
 We believe that from 12 to 20 tons are made weekly in 
 St. Helens alone, while in 1871 the total make amounted 
 to 750 tons, having a value of 105/. per ton, or an aggre- 
 gate value of nearly 80,000/. The only improvement we 
 have to indicate in reference to this manufacture, is one 
 which was proposed by Mr. Walter Weldon after having 
 performed a great number of experiments, showing the 
 feasibility of the proposition, although it has not yet been 
 adopted, so far as we can learn. It consists in the use of 
 magnesia instead of lime, thus obtaining a residue of 
 magnesic chloride instead of calcic chloride, and from 
 which the magnesia is constantly regenerated with the 
 production of hydrochloric acid, by simple evaporation 
 to dryness in a current of steam and continued roasting. 
 Mg01 2 + H 2 0=MgO + 2HC1. 
 
 The hydrochloric acid can be condensed in the ordinary 
 way for further use. 
 
 Magnesia may be readily obtained, as stated elsewhere, 
 by simple roasting of the native carbonate which occurs 
 in a nearly pure form as Greek stone or magnesite. En 
 passant, it may be remarked that Epsom salts (Mg S0 4 ) 
 are made from this magnesite by the action of sulphuric 
 acid. No less than 590 tons are made annually in the 
 Tyne district (1867), and have an aggregate value of 
 4,720. Epsom salts are also made by Mr. Gamble, at 
 St. Helens. 
 
234 THE ALKALI TRADE. 
 
 CHAPTEE XVIII. 
 
 GENERAL CONSIDERATIONS REGARDING THE ALKALI TRADE ; 
 CHEMICAL CLIMATOLOGY, ETC. 
 
 IN the foregoing chapters we have studied the growth of 
 the alkali trade from its beginnings, and at all stages it 
 is evident that the improvements which have been from 
 time to time effected in this large industry, have been 
 chiefly directed to the utilisation of once waste products. 
 In fact, its history, like that of the English nation, is one 
 of slow progression, in which advancement has been 
 made chiefly by a process of evolution rather than by 
 one of revolution. 
 
 The question before the manufacturer takes the form 
 of highest possible profits from the smallest possible out- 
 lay ; and in England, where labour is high-priced and 
 competition so powerful, the quantity of ' turn out ' has 
 been the main object in view. Here and there, owing 
 to this system, and to the gigantic scale on which the 
 various manufactures we have described, are practised, 
 excellence of production has at times been to some extent 
 forgotten. On the whole, however, owing to the inti- 
 mate acquaintance of our manufacturers with the prac- 
 tical working of the various processes, this country is far 
 in advance of all others in chemical industry. At the 
 same time it must be confessed, to our shame, perhaps, 
 that while this is so, the attention of manufacturers is 
 
CONDENSATION OF ACID VAPOURS. 235 
 
 more readily commanded by the voice which proclaims a 
 reduction in the cost of producing rather than by one 
 setting forth the merits of an entirely new process. 
 In other words, they are far more 'practical' than 
 scientific. The element of competition, however, atones 
 in some measure for this evil, and if one producer, by 
 the utilisation of a waste product, or by the adoption 
 of an innovation, can enter the market and sell with 
 greater advantage than his compeers, they are generally 
 not slow to follow. 
 
 It is therefore the object of manufacturers, for the 
 sake of their own purse with them the strongest argu- 
 ment to make the most out of a certain outlay, and this 
 can best be done by working with care, and keeping 
 down waste as low as possible. Such waste proves a 
 nuisance as well as an expense. 
 
 We have seen that in years gone by, most of the 
 hydrochloric acid resulting from the decomposition of 
 salt was allowed to escape into the atmosphere. This 
 caused residential habitation in certain districts to be quite 
 impossible, while the noxious vapour rendered the sur- 
 rounding country desolate, as if stricken with some dire 
 disease. The grass perished, the trees died, crops were 
 ruined, and the birds and insects departed or became 
 extinct, until owners of property brought numerous 
 actions for damages against the proprietors of the works 
 from which the evil gases were generated. The evil 
 became so serious in 1863, that the Legislature interfered, 
 on the suggestion of the late Earl of Derby, and passed 
 an Act which compelled manufacturers of alkali to con- 
 dense no less than 95 per cent, of the total muriatic acid 
 evolved in the salt-cake furnaces. The means of effecting 
 
236 THE ALKALI TKADE. 
 
 sucli absorption were ready to hand, and had, indeed, 
 been devised by Mr. Gossage long before their use was 
 rendered imperative. Almost simultaneously there came 
 an increased demand for bleaching powder, owing to the 
 causes we have previously sketched, and it is from that 
 once wasted hydrochloric acid that the demand for 
 ' bleach ' is now fed, by the manufacture of chlorine 
 therefrom. 
 
 As time went on, there arose the copper extraction 
 industry (by the wet method), but it brought with it 
 another evil, for in the process of roasting the burnt 
 pyrites with salt, much hydrochloric acid and some 
 sulphurous anhydride is evolved. In the meantime, the 
 Act of 1863 only applied to soda works, and the ex- 
 tractors of copper for a time went free. In 1874, how- 
 ever, the Act was amended, and copper and sulphuric 
 acid works were placed under similar restrictions to those 
 above set forth. The result is that, as regards hydro- 
 chloric acid, not only is 95 per cent, of the total quantity 
 evolved, condensed, but in many works even 99 per cent, 
 is saved, while cases rarely occur in which the quantity 
 of hydrochloric acid contained in the chimney-gas ex- 
 ceeds one-fifth of a grain per cubic foot. Considerable 
 evil is nevertheless exerted by the escape of muriatic 
 gas in the immediate vicinity of alkali works. This 
 escape results from the method of raking the finished 
 salt-cake out upon the open ground, when all the residual 
 acid gas enclosed between the solid parts of the charge 
 is liberated, and exerts a most deleterious influence upon 
 the workmen, who generally stand at their work with 
 wet rags in their mouth. Should the salt cake be im- 
 perfectly roasted, the evil is of course much greater. 
 
NUISANCES CAUSED BY ESCAPE OF VAPOURS. 237 
 
 These matters are, however, carefully watched by the 
 inspectors appointed under the above Act of Parliament, 
 while those furnaces and methods which have been more 
 recently devised for manufacturing salt-cake, avoid, in 
 great measure, even this residual evil, either by causing 
 the charge when finished to cool in closed receptacles, 
 or by effecting a more complete decomposition of the 
 salt. 
 
 Another nuisance is created by the escape of sul- 
 phurous anhydride and nitrous vapours into the atmo- 
 sphere, an evil which was of course incomparably greater 
 in past days, when the chamber gases were passed direct 
 into the chimney shaft, than now, when Gay-Lussac's and 
 Glover's towers are so widely used. In badly managed 
 works, the quantity of sulphur in every form contained 
 in the residual chamber gas often amounts to 16 grains 
 per cubic foot (Eoscoe), while it should certainly not 
 exceed, when proper care is taken, 1 grain per cubic 
 foot. The gas issuing from the chimney shaft should not 
 contain more than ^ grain of sulphur per cubic foot, half 
 of which, however, is derived from the furnaces wherein 
 coal or coke is burnt. 
 
 In well-conducted works there is but little escape of 
 chlorine ; when it is the case, from carelessness or other- 
 wise, it proves one of the most painful of noxious influ- 
 ences. The workmen are necessarily exposed to it in 
 some measure, when withdrawing the finished bleach from 
 the chambers ; but in addition to this, and an occasional 
 leakage from the stills, or pipes which convey the gas, 
 little evil results owing to the escape of chlorine. 
 
 During the process of ' salting down ' the caustic pots, 
 a considerable nuisance is often caused by the escape of 
 
238 THE ALKALI TRADE. 
 
 hot particles of salt into the atmosphere. When the salt 
 is thrown into the red-hot caustic, it decrepitates and 
 throws up a fine cloud of hot spray, which is very painful 
 to persons in the neighbourhood. The nuisance may be, 
 and is, avoided in great part by keeping the pots duly 
 covered during the proceeding. 
 
 Passing from waste gases to liquids, we find far less 
 cause for complaint than in years gone by, when nearly 
 all the waste liquors of acid, chloride of manganese were 
 discharged into the water streams. Such a waste, beyond 
 the loss of manganese, exerted most deleterious influ- 
 ences, by ruining the potability of the water thus con- 
 taminated, and by destroying the fish living in the 
 streams. Not only so, but the acid thus so readily 
 spread over the surrounding neighbourhood constantly 
 came in contact with vat waste, and thereby liberated 
 volumes of sulphuretted hydrogen and sulphurous anhy- 
 dride into the atmosphere, to the distress and injury of 
 resident people. Now, however, since the introduction 
 of Weldon's process, this evil is greatly obviated, yet not 
 entirely, for although chloride of calcium is of far less 
 value to the manufacturer, who can therefore afford the 
 better to throw it away in preference to mixed hydro- 
 chloric acid and chloride of manganese, its presence by 
 no means improves the quality of water. This waste 
 product, therefore, is an evil which must be swept away 
 sooner or later ; and in previous chapters we have in- 
 dicated the means proposed by Mr. Weldon to effect 
 this step, viz., the substitution of magnesia for lime 
 in his process, and the utilisation, by regeneration, of 
 it and the chlorine with which it is in combination as 
 chloride. 
 
ALKALI WASTE AND COAL SMOKE. 239 
 
 The greatest evil in the alkali trade, soda waste, we 
 have already adverted to greatest, because of the valu- 
 able ingredients it contains though a waste product, and 
 on account of a constant evolution of sulphuretted hydro- 
 gen from it, by the action of water and carbonic acid upon 
 the sulphides it contains. While, as we have seen, some 
 sulphur is regenerated from it by Mond's process, and yet 
 more by Mactear's, most of the enormous quantity of alkali 
 waste produced in this country finds no better use than 
 to fill up pits from which clay has been taken. Mean- 
 while, there are ranges of hills of it in various places, 
 whose presence proclaim the imperfection of chemical 
 knowledge and practical skill, although both are so 
 boasted in the present day. 
 
 There is, moreover, another nuisance in connection 
 with the alkali as well as other trades, which is, perhaps, 
 of as much or greater import than ' vat waste ' or ' blue- 
 billy,' as it is called, namely, coal-smoke. Manufacturers 
 may build their chimney-shafts ever so high, aye, even to 
 top Egypt's proudest pyramid, but the smoke still rolls 
 out its black stream ruthlessly, and, although it is dif- 
 fused, it is not destroyed. Besides the mischief it creates, 
 both on the bodily health and the mental peace of man- 
 kind, it speaks of wasted fuel and dissipated energy. 
 Even in this direction, however, there is some hope of 
 improvement, and of late, many attempts have been made 
 to construct furnaces and stoking machines, which may 
 prove serviceable in saving fuel, while at the same time 
 the escaping smoke is lessened. These stoking machines 
 aim at feeding into the furnace a continuous supply of 
 fuel at the rate required, while providing a proper pro- 
 portion of air to combine with the carbon and combus- 
 
240 THE ALKALI TRADE. 
 
 tible gases ; to effect the perfect mixing of the air and 
 gases ; and, lastly, to prevent the resulting mixture from 
 reduction in temperature below that of ignition, before 
 the combustion is complete. These are difficult problems 
 to solve, and the foremost chemical engineers of the clay 
 have but begun the attempt at solution. It is satisfac- 
 tory, however, to know there is a beginning, and we may 
 therefore hope for better things eventually. 
 
 In closing this chapter, we cannot refrain from a 
 mention of the able services rendered in connection with 
 the science of chemical climatology as related to the 
 alkali trade, by Dr. Angus Smith, Mr. Fletcher, and Mr. 
 James Mactear. For great difficulties are experienced 
 in determining the rate at which gases issue from chim- 
 neys, seeing that the whole volume contained in a shaft 
 does not move at one uniform rate. Beyond the suc- 
 cessful removal of these obstacles, these gentlemen have 
 also constructed most accurate anemometers, and have, 
 indeed, laid the foundation of a science in this direction. 
 
 Manufacturers would do well to appreciate more fully 
 than they do at present, that science is slow to progress, 
 and on that progress all improvement in industrial appli- 
 cations depends. Let them, therefore, encourage its 
 development by employing competent chemists ; and not 
 only so, but rather aid research than war against it, as 
 they have too often done in the past. They cannot 
 hinder the current of knowledge in its advance, but they 
 can help to increase its rate of movement. In another 
 direction they can also benefit humanity, by creating the 
 means whereby their workmen may elevate themselves 
 and train their children, in a better way than is to be 
 witnessed now. Men have other relations one to the 
 
THE DUTIES OF MANUFACTURERS. 241 
 
 other than those included in the commercial world of 
 capital and labour, and this better side of life cannot be 
 hidden even by the shadow of the Stock Exchange and 
 the marts. Indeed, life may be compared to a spectrum 
 with its bright and dark lines. 
 
242 THE ALKALI TRADE. 
 
 CHAPTEE XIX. 
 
 STATISTICS OF THE ALKALI TRADE. 
 
 THE alkali trade, as it has been described in the fore- 
 going chapters, may be said to be exclusively the growth 
 of this century. The articles manufactured constitute, in 
 many instances, the raw materials for other trades and 
 industries, so that the alkali trade is in some measure 
 dependent on the general state of trade in this and other 
 countries. Consequently, great fluctuations in price and 
 profit are experienced from time to time, a state of things 
 often intensified by too rapid extension of plant beyond 
 even the demand for the various manufactured products. 
 We have already given many statistics relating to the 
 articles consumed and manufactured in the alkali trade, 
 under the headings of individual substances ; here, there- 
 fore, we shall only give some figures regarding this in- 
 dustry, as it was fifteen years ago, and, more particularly, 
 as it exists now. It should be remarked that it is a most 
 difficult matter to make an accurate computation of the 
 whole state of the trade, and, indeed, the only approxi- 
 mate one that has been constructed refers to the year 
 1866.. Originally, as we have seen, in the days of the 
 beginning of the trade, comparatively small amounts of 
 products were manufactured, and these were sold at 
 prices which, viewed against those now obtaining, seem 
 ridiculously high. Thus, in 1805, bleaching powder was 
 
STATISTICS OF THE ALKALI TRADE. 243 
 
 worth 120/. per ton; in 1868, its price was 10/. 125. per 
 ton, while to-day it has a value of 4/. or 5/. per ton. 
 Again, in 1801, alkali sold at about 49/. 5s. per ton, and 
 in 1806, soda crystals sold at about 60/. per ton ; to-day 
 it is 41. 15s. per ton. In 1736 sulphuric acid cost 2s. 
 per lb., or 128/. per ton, while in 1866 it cost 6/. per ton; 
 to-day it has a value of 5/. per ton. Bicarbonate of soda 
 now sells at 17 per ton ; caustic soda of 60 per cent, at 
 13/. per ton, and chlorate of potassium at d. per lb. 
 
 Between the years 1852 and 1862, the total alkali 
 trade more than doubled, while in the latter year the 
 annual value of finished products amounted to 2,500,000/. 
 At that date, the raw materials consumed per annum were 
 as follow : Salt, 254,000 tons ; coal, 961,000 ; limestone 
 and chalk, 280,500 ; pyrites, 264,000 ; nitrate of soda, 
 8,300 ; manganese, 33,000 ; timber (for casks), 33,000 
 total, 1,833,800 tons. There was a total capital em- 
 ployed of 2,0 10,00(M. 
 
 It has been calculated that in 1861 there were about 
 fifty soda works in Great Britain, with about the following 
 quantities of ' turn out ' : 
 
 Articles Manufactured 
 
 Per week 
 
 Annually 
 
 
 Tons 
 
 Tona 
 
 Soda ash .... 
 
 3,000 
 
 156,000 
 
 Soda crystals .... 
 
 2,000 
 
 104,000 
 
 Soda bicarbonate . 
 
 250 
 
 13,000 
 
 Bleaching powder . 
 
 400 
 
 20,800 
 
 Employing about 10,000 persons, exclusive of mining 
 operations and transportations, etc. Multiplying the 
 above quantities in the first column by 52, to get the an- 
 nual products, we obtain those in the second column. 
 Now, according to Messrs. Schunck, Smith, and 
 
 B 2 
 
244 
 
 THE ALKALI TRADE. 
 
 Eoscoe, the Lancashire district alone, produced in 1861 
 the following quantities : 
 
 Name of Article 
 
 Per week 
 
 Annually 
 
 
 Tons 
 
 Tons 
 
 Common salt decomposed . 
 
 2,600 
 
 135,000 
 
 Sulphuric acid (1-6) used . 
 
 3,110 
 
 161,720 
 
 Hydrochloric acid (1.5) produced 
 
 3,800 
 
 176,800 
 
 Soda ash .... sold 
 
 1,800 
 
 93,600 
 
 Salt-cake . . 
 
 180 
 
 9,360 
 
 Soda crystals (N"a 2 C0 3 10H 2 0),, 
 
 170 
 
 8,840 
 
 Bicarbonate . . . 
 
 225 
 
 11,700 
 
 Caustic soda . . 
 
 90 
 
 4,680 
 
 These quantities were calculated from the returns 
 made by twenty-five works, so that, in comparison with 
 the above figures relating to the whole of Great Britain, 
 a very good idea is obtained of the distribution, so to 
 speak, of the trade at that time. 
 
 Advancing to 1866, and acting on very good returns 
 from twenty manufacturers in the Lancashire district, 
 with the estimated production of six, it is found that 
 194,000 tons of salt were decomposed, with the produc- 
 tion of the following quantities : 
 
 Quantity returned 
 
 
 Price per ton 
 
 Total amount 
 
 Soda crystals 
 Soda ash and refined alkali 
 Caustic soda 
 Bicarbonate of soda 
 Sulphate of soda. 
 Bleaching powder. 
 Bleach liquor 
 
 Tons 
 24,978 
 87,314 
 11,213 
 6,457 
 32,137 
 20,006 
 5,871 
 
 s. d. 
 600 
 11 
 20 
 18 
 450 
 14 
 300 
 
 & s. d. 
 149,868 
 960,454 
 224,260 
 116,226 
 136,582 5 
 280,084 
 17,613 
 
 Tons .... 
 
 Oil of vitriol for sale 
 Muriatic acid 
 
 187,976 
 
 18,592 
 13,819 
 
 Total . 
 
 600 
 15 
 
 1,885,087 5 
 
 111,552 
 10,364 5 
 
 Total tons . 
 
 220,387 
 
 Total value 
 
 2,007,003 10 
 
STATISTICS OF THE ALKALI TRADE. 
 
 245 
 
 In the Tyne district during the same year about 
 157,000 tons of salt were decomposed, and the following 
 amounts of various products turned out : 
 
 Quantity returned 
 
 Trice per ton 
 
 Total amount 
 
 
 Tons. 
 
 *. d. 
 
 s. d. 
 
 Soda crystals . 
 Soda ash or alkali 
 Caustic soda, 70 pei cent 
 Bicarbonate of soda 
 Sulphate of soda 
 Bleaching powder 
 Epsom salts 
 Glauber salts . 
 Sulphate of copper 
 Hyposulphite of soda 
 Chloride of manganese 
 Oil of vitriol for sale 
 Muriatic acid . 
 
 86,000 
 
 74,000 
 3,720 
 11,000 
 2,400 
 27,000 
 590 
 20 
 200 
 400 
 1,300 
 9,000 
 700 
 
 5 10 
 11 
 
 26 
 18 
 450 
 14 
 800 
 6 15 
 26 
 18 
 3 10 
 400 
 300 
 
 473,000 
 814,000 
 96,720 
 198,000 
 10,200 
 278,000 
 4,720 
 135 
 5,200 
 7,200 
 4,550 
 36,000 
 2,100 
 
 Total tons 
 
 216,330 
 
 Total value 1,929,825 
 
 Thus it will be seen that the exten^jrf the alkali trade in 
 the two great districts of Lancashire and the Tyne was 
 nearly equal in terms of production and value. In regard 
 to the Tyne district (1867), the raw materials consumed 
 for producing the above quantities consisted of pyrites, 
 salt, chalk, timber, coal, and manganese, and amounted 
 to 1,070,000 tons, with an aggregate value of 830,925J. 
 
 6 The number of workmen employed in the soda 
 works on the Tyne is estimated to be 8,000 ; and the 
 number of vessels which discharged cargoes of raw mate- 
 rials at soda works in 1867 was 5,000. The floating and 
 fixed capital employed in soda works on the Tyne is 
 2,000,000/. to 2,500,000/.' (R. Calvert Clapham.) 
 
 Taking the raw materials consumed in Lancashire to 
 have had a total value of about 869,600J. in 1866-67, 
 we get the following computation for the whole of Eng- 
 land in that year : Eaw materials, 1,700,525. ; manufac- 
 tured ditto, 3,936,829/. ; capital, 5,000,000/. 
 
246 THE ALKALI TEADE. 
 
 Since the year of which we have been writing, no 
 very reliable statistics are forthcoming for the collective 
 trade ; but we know that the production of particular 
 articles has undergone a large increase notably, caustic 
 soda and bleaching powder. Indeed, the production of 
 the latter article has more than doubled ; while sulphur 
 regenerated from the alkali waste and certain other re- 
 generated substances, have to be added to the list of 
 manufactured articles. The manufacture of the speciali- 
 ties of the Tyne district sulphate of copper and hypo- 
 sulphite of soda has diminished. 
 
 Apart from exact statistics, it has been calculated that 
 the decomposition of salt in the Tyne district during 
 1874, exceed 202,000 tons, and as it has also undergone 
 an increase in the Lancashire district, perhaps it may be 
 said that about 500,000 tons of salt are now annually 
 consumed in Great Britain. It must not be forgotten 
 that the Glasgow chemical industry is very large, and 
 further on, we shall again allude to it. 
 
 The following figures show the state of the Tyne 
 alkali trade in 1874, and in connection with this matter 
 it should be remembered that it gives rise to a large 
 shipping trade in addition. 
 
 Inwards to the extent of ... 622,000 tons 
 Coals (only a small part by shipping) . 800,000 
 
 1,422,000 
 Outwards, including packages . . 382,000 
 
 Totals . . 1,804,000 
 
 Value of raw materials . . . 1,600,000 
 Computed value of manufactured goods 2,630,000 
 Weight in tons of manufactured goods 382,000 
 Weight carried in all by sea and rail . 2,126,000 tons 
 
 These weights and values do not include the mate- 
 rials u?ed in buildings, plants, and repairs, which, from 
 
THE GLASGOW CHEMICAL INDUSTRY. 
 
 247 
 
 the changes in. the processes of manufacture introduced 
 from time to time, and the nature of the work which has 
 to be done, require constant renewal, etc. The number 
 of hands employed in the Tyne district are about 10,000, 
 and the wages for a year exceed 700,000/. 
 
 We have referred above, to the chemical industry of 
 Glasgow and the Clyde Valley. The share taken by 
 Scotland in the alkali trade has from its commencement 
 been very considerable, and at the present time, besides 
 the large works at St. Eollox, there are four or five others. 
 The St. Eollox works cover fifty acres, and 1,200 men 
 are employed, while the total raw products consumed, 
 amount to more than 80,000 tons, excluding coal. 
 
 In conclusion, we give a table, calculated by Mr. 
 James Mactear, of St. Eollox, showing the raw mate- 
 rials, products, and bye-products of an alkali works, based 
 on 100 tons pyrites : 
 
 100 pyrites 
 
 I 
 
 1-88 nitrate of soda 
 I 
 
 70 burnt ore 
 
 Sold to Copper Extracting Co. 
 
 163-35 salt 
 I 
 
 136-3 sulphuric acid 
 
 176-38 sulphate of soda 
 
 I 
 
 274-4 hydrochloric acid 
 at 1-16 sp. gr. 
 
 47'45 manganese 
 
 1 
 
 36-81 lime 
 1 
 
 65-45 bleaching powder 
 
 67-02 coal 123-46 limestone 
 
 I I 
 
 42-75 recovered manganese 
 17-63 lime 
 
 134-05 soda ash at 48 per cent, alkali 
 or 91-63 caustic soda at 60 per cent, alkali 
 or 242-8 soda crystals 
 
 111-12 waste 
 
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 **- Where not otherwise stated, all of the Books in this Catalogue are bound 
 in muslin. 
 
 AMATEUR MECHANICS' WORKSHOP: 
 
 A treatise containing plain and concise directions for the manipula- 
 tion of Wood and Metals, including Casting, Forging, Brazing, 
 Soldering and Carpentry. By the author of the " Lathe and It* 
 Uses." Seventh edition. Illustrated. 8vo. . . . $2.50 
 
 ANDRES. A Practical Treatise on the Fabrication of Volatile 
 and Fat Varnishes, Lacquers, Siccatives and Sealing- 
 Waxes. 
 
 From the German of ERWIN ANDRES, Manufacturer of Varnishet 
 and Lacquers. With additions on the Manufacture and Application 
 of Varnishes, Stains for Wood, Horn, Ivory, Bone and Leather. 
 From the German of DR. EMIL W'INCKLER and Louis E. ANDES, 
 The whole translated and edited by WILLIAM T. BRANNT. With n 
 illustrations. I2mo. . $2.50 
 
 ARLOT. A Complete Guide for Coach Painters : 
 
 Translated from the French of M. ARLOT, Coach Painter, for 
 eleven years Foreman of Painting to M. Eherler, Coach Maker, 
 Paris. By A. A. FESQUET, Chemist and Engineer. To whicb is 
 added an Appendix, containing Information respecting the Materiak 
 and the Practice of Coach and Car Painting and Varnishing in th 
 United States and Great Britain. I2mo. . . . 1.25 
 
HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
 ARMENGAUD, AMOROUX, AND JOHNSON. The Practi- 
 cal Draughtsman's Book of Industrial Design, and Ma* 
 chinist's and Engineer's Drawing Companion : 
 
 Forming a Complete Course of Mechanical Engineering and Archi- 
 tectural Drawing. From the French of M. Armengaud the elder, 
 Prof, of Design in the Conservatoire of Arts and Industry, Paris, and 
 MM. Armengaud the younger, and Amoroux, Civil Engineers. Re- 
 written and arranged with additional matter and plates, selections from 
 and examples of the most useful and generally employed mechanism 
 of the day. By WILLIAM JOHNSON, Assoc. Inst. C. E. Illustrated 
 by fifty folio steel plates, and fifty wood-cuts. A new edition, 4to,, 
 
 half morocco $10.00 
 
 ARMSTRONG. The Construction and Management of Steam 
 
 Boilers : 
 
 By R. ARMSTRONG, C. E. With an Appendix by ROBERT MALLET, 
 C. E., F. R. S. Seventh Edition. Illustrated, i vol. I2mo. 75 
 
 ARROWSMITH. Paper-Hanger's Companion : 
 
 A Treatise in which the Practical Operations of the Trade are 
 Systematically laid down : with Copious Directions Preparatory to 
 Papering; Preventives against the Effect of Damp on Walls; the 
 various Cements and Pastes Adapted to the Several Purposes 01 
 the Trade ; Observations and Directions for the Panelling and 
 Ornamenting of Rooms, etc. By JAMES ARROWSMITH. J2mo., 
 cloth $1.25 
 
 ASHTON. The Theory and Practice of the Art of Designing 
 
 Fancy Cotton and Woollen Cloths from Sample : 
 Giving full instructions for reducing drafts, as well as the methods of 
 spooling and making out harness for cross drafts and finding any re- 
 quired reed; with calculations and tables of yarn. By FREDERIC T. 
 ASHTON, Designer, West Pittsfield, Mass. With fifty -two illustrations. 
 One vol. folio $6.co 
 
 ASKINSON. Perfumes and their Preparation : 
 
 A Comprehensive Treatise on Perfumery, containing Complete 
 Directions for Making Handkerchief Perfumes, Smelling-Salts. 
 Sachets, Fumigating Pastils ; Preparations for the Care of the Skin, 
 the Mouth, the Hair; Cosmetics, Hair Dyes, and other Toilet 
 Articles. By G.W. ASKINSON. Translated from the German by ISIDOR 
 FURST. Revised by CHARLES RICE. 32 Illustrations. 8vo. $3.00 
 
 BAIRD. Miscellaneous Papers on Economic Questions. 
 By Henry Carey Baird. {In preparation.} 
 
 BAIRD. The American Cotton Spinner, anc Manager's and 
 
 Carder's Guide: 
 
 A Practical Treatise on Cotton Spinning ; giving the Dimensions and 
 Speed of Machinery, Draught and Twist Calculations, -tr.. ; with 
 notices of recent Improvements: together with Rules and Examples 
 ror making changes in the sizes and numbers of Roving and Yarn. 
 Compiled from the papers of the late ROBERT H. BAIRD. I2mo. 
 
HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
 BAIRD. Standard Wages Computing Tables : 
 
 An Improvement in all former Methods of Computation, so arranged 
 that wages for days, hours, or fractions of hours, at a specified rate 
 per day or hour, may be ascertained at a glance. By T. SPANGLER 
 BAIRD. Oblong folio ....... $5.00 
 
 BAKER. Long-Span Railway Bridges : 
 
 Comprising Investigations of the Comparative Theoretical and 
 Practical Advantages of the various Adopted or Proposed Type 
 Systems of Construction ; with numerous Formulae and Tables. By 
 B. BAKER. I2mo. $1.50 
 
 BAKER. The Mathematical Theory of the Steam-Engine : 
 With Rules at length, and Examples worked out for the use of 
 Practical Men. By T. BAKER, C. E., with numerous Diagrams. 
 Sixth Edition, Revised by Prof. J. R. YOUNG. I2mo. . 75 
 
 BARLOW. The History and Principles of Weaving, by 
 
 Hand and by Power : 
 
 Reprinted, with Considerable Additions, from " Engineering," with 
 a chapter on Lace-making Machinery, reprinted from the Journal df 
 the "Society of Arts." By ALFRED BARLOW. With several hundred 
 illustrations. 8vo., 443 pages . . * . . . $10.00 
 
 BARR. A Practical Treatise on the Combustion of Coal: 
 Including descriptions of various mechanical devices for the Eco- 
 nomic Generation of Heat by the Combustion of Fuel, whether solid, 
 liquid or gaseous. 8vo . $2.50 
 
 BARR. A Practical Treatise on High Pressure Steam Boilers: 
 Including Results of Recent Experimental Tests of Boiler Materials, 
 together with a Description of Approved Safety Apparatus, Steam 
 Pumps, Injectors and Economizers in actual use. By WM. M. BARR. 
 204 Illustrations. 8vo $3- 
 
 BAUERMAN. A Treatise on the Metallurgy of Iron : 
 
 Containing Outlines of the History of Iron Manufacture, Methods of 
 Assay, and Analysis of Iron Ores, Processes of Manufacture of Iron 
 and Steel, etc., etc. By H. BAUERMAN, F. G. S., Associate of the 
 Royal School of Mines. Fifth Edition, Revised and Enlarged. 
 Illustrated with numerous Wood Engravings from Drawings by J. B. 
 JORDAN. 1 2mo Jjte.oc 
 
 BAYLES. House Drainage and Water Service : 
 
 In Cities, Villages and Rural Neighborhoods. With Incidental Con. 
 sideration of Certain Causes Affecting the Healthfulness of Dwell- 
 ings. By JAMES C. BAYLES, Editor of " The Iron Age " and " The 
 Metal Worker." With numerous illustrations. 8vo. cloth, 
 
 BEANS. A Treatise on Railway Curves and Location of 
 
 Railroads : 
 By E. W. BEANS, C. E. Illustrated. I2mo. Tucks . $1.50 
 
 BECKETT. A Rudimentary Treatise on Clocks, and Watches 
 
 and Bells : 
 
 By Sir EDMUND BECKETT, Bart., LL. D., Q. C. F. R. A. S. With 
 numerous illustrations. Seventh Edition, Revised and Enlarged. 
 lamo $2.25 
 
HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
 BELL. Carpentry Made Easy: 
 
 Or, The Science and Art of Framing on a New and Improved 
 System. With Specific Instructions for Building Balloon Frames, Barn 
 Frames, Mill Frames, Warehouses, Church Spires, etc. Comprising 
 also a System of Bridge Building, with Bills, Estimates of Cost, and 
 valuable Tables. Illustrated by forty-four plates, comprising .nearly 
 200 figures. By WILLIAM E. BELL, Architect and Practical Builder. 
 8vo. .......... $5.00 
 
 BEMROSE. Fret-Cutting and Perforated Carving: 
 
 With fifty-three practical illustrations. By W. BEMROSE, JR. I vol. 
 quarto .......... $2.50 
 
 BEMROSE. Manual of Buhl-work and Marquetry: 
 
 With Practical Instructions for Learners, and ninety colored designs 
 By W. BEMROSE, JR. i vol. quarto .... $3.00 
 
 BEMROSE. Manual of Wood Carving: 
 
 With Practical Illustrations for Learners of the Art, and Original and 
 Selected Designs. By WILLIAM BEMROSE, JR. With an Intro- 
 duction by LLEWELLYN JEWITT, F. S. A., etc. With 128 illustra- 
 tions, 4to. $2.50 
 
 BILLINGS. Tobacco : 
 
 Its History, Variety, Culture, Manufacture, Commerce, and Various 
 Modes of Use. By E. R. BILLINGS. Illustrated by nearly 200 
 engravings. 8vo. ........ $3.O 
 
 BIRD. The American Practical Dyers' Companion: 
 
 Comprising a Description of the Principal Dye-Stuffs and Chemicals 
 used in Dyeing, their Natures and Uses ; Mordants, and How Made ; 
 with the best American, English, French and German processes for 
 Bleaching and Dyeing Silk, Wool, Cotton, Linen, Flannel, Felt, 
 Dress Goods, Mixed and Hosiery Yarns, Feathers, Grass, Felt, Fur, 
 Wool, and Straw Hats, Jute Yarn, Vegetable Ivory, Mats, Skins, 
 Furs, Leather, etc., etc. By Wood, Aniline, and other Processes, 
 together with Remarks on Finishing Agents, and Instructions in the 
 Finishing of Fabrics, Substitutes for Indigo, Water- Proofing of 
 Materials, Tests and Purification of Water, Manufacture of Aniline 
 and other New Dye Wares, Harmonizing Colors, etc., etc. ; embrac- 
 ing in all over 800 Receipts for Colors and Shades, accompanied by 
 170 Dyed Samples of Raw Materials and Fabrics. By F. J. BIRD. 
 Practical Dyer, Author of " The Dyers' Hand-Book. " 8vo. $10.00 
 
 BLINN. A Practical Workshop Companion for Tin, Sheet- 
 Iron, and Copper-plate Workers : 
 
 Containing Rules for describing various kinds of Patterns used by 
 Tin, Sheet-Iron and Copper-plate Workers; Practical Geometry -, 
 Mensuration of Surfaces and Solids ; Tables of the Weights of 
 Metals, Lead-pipe, etc.; Tables of Areas and Circumference* 
 of Circles ; Japan, Varnishes, Lackers, Cements, Compositions, etc., 
 etc. By LEROY J. BLINN, Master Mechanic. With One Hundred 
 and Seventy Illustrations. I2mo. . . . . . #2.50 
 
HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
 BOOTH. Marble Worker's Manual: 
 
 Containing Practical Information respecting Marbles in general, theif 
 Cutting, Working and Polishing ; Veneering of Marble ; Mosaics ; 
 Composition and Use of Artificial Marble, Stuccos, Cements, Receipts, 
 Secrets, etc., etc. Translated from the French by M. L. BOOTH. 
 With an Appendix concerning American Marbles. I2mo., cloth $1.50 
 BDOTH and MORFIT. The Encyclopaedia of Chemistry, 
 
 Practical and Theoretical : 
 
 Embracing its application to the Arts, Metallurgy, Mineralogy, 
 Geology, Medicine and Pharmacy. By JAMES C. BOOTH, Melter 
 and Refiner in the United States Mint, Professor of Applied Chem- 
 istry in the Franklin Institute, etc., assisted by CAMPBELL MORFIT, 
 author of " Chemical Manipulations," etc. Seventh Edition. Com- 
 plete in one volume, royal 8vo., 978 pages, with numerous wood-cuts 
 and other illustrations ....... $3-5 
 
 BRAM WELL. The Wool Carder's Vade-Mecum* 
 
 A Complete Manual of the Art of Carding Textile Fabrics. By W 
 C. BRAMWELL. Third Edition, revised and enlarged. Illustrated. 
 Pp. 400. I2mo ....... . . $2.50 
 
 BRANNT. A Practical Treatise on Animal and Vegetable 
 
 Fats and Oils : 
 
 Comprising both Fixed and Volatile Oils, their Physical and Chemi- 
 cal Properties and Uses, the Manner of Extracting and Refining 
 them, and Practical Rules for Testing them ; as well as the Manu- 
 facture of Artificial Butter, Lubricants, including Mineral Lubricating 
 Oils, etc., and on Ozokerite. Edited chiefly from the German of 
 DRS. KARL SCHAEDLER, G. W. ASKINSON, and RICHARD BRUNNER, 
 with Additions and Lists of American Patents relating to the Extrac- 
 tion, Rendering, Refining, Decomposing, and Bleaching of Fats and 
 Oils. By WILLIAM T. BRANNT. Illustrated by 244 engravings. 
 739 pages. 8vo ......... $7.50 
 
 BRANNT. A Practical Treatise on the Manufacture of Soap 
 
 and Candles : 
 
 Based upon the most Recent Experiences in the Practice and Science ; 
 comprising the Chemistry, Raw Materials, Machinery, and Utensils 
 and Various Processes of Manufacture, including a great variety of 
 formulas. Edited chiefly from the German of Dr. C. Deite, A. 
 Engelhardt, Dr. C. Schaedler and others; with additions and lists 
 of American Patents relating to these subjects. By WM. T. BRANNT. 
 Illustrated by 163 engravings. 677 pages. 8vo. . . $7-S 
 
 . A Practical Treatise on the Raw Materials and the 
 Distillation and Rectification of Alcohol, and the Prepara- 
 tion of Alcoholic Liquors, Liqueurs, Cordials, Bitters, etc. : 
 Edited chiefly from the German of Dr. K. Stammer, l)r. F. Eisner, 
 and E. Schubert. By WM. T. BRANNT. Illustrated by thirty-one 
 engravings. I2mo. ....... $2.50 
 
HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
 BRANNT WAHL. The Techno- Chemical Receipt Book: 
 
 Containing several thousand Receipts covering the latest, most < 
 portant, and most useful discoveries in Chemical Technology, an<? 
 their Practical Application in the Arts and the Industries. Editec 
 chiefly from the German of Drs. Winckler, Eisner, Heintze, Mier 
 zinski, Jacobsen, Roller, and Heinzerling, with additions by WM. ']. 
 BRANNT and WM. H. WAHL, PH. D. Illustrated by 78 engraving-* 
 israo. 495 pages ..... $2 oa 
 
 BROWN. Five Hundred and Seven Mechanical Movements . 
 Embracing all those which are most important in Dynamics, Hv- 
 draulics, Hydrostatics, Pneumatics, Steam-Engines, Mill and other 
 Gearing, Presses, Horology and Miscellaneous Machinery; and in- 
 cluding many movements never before published, and several c.f 
 which have only recently come into use. By HENRY T. BROWN 
 I2mo. .......... $i.oc 
 
 BUCKM ASTER. The Elements of Mechanical Physics: 
 By J. C. BUCKMASTER. Illustrated with numerous engravings. 
 I2mo $1.00 
 
 BULLOCK. The American Cottage Builder : 
 A Series of Designs, Plans and Specifications, from $200 to $20,000, 
 for Homes for the People; together with Warming, Ventilation, 
 Drainage, Painting and Landscape Gardening. By JOHN BULLOCK, 
 Architect and Editor of "The Rudiments of Architecture and 
 Building," etc., etc. Illustrated by 75 engravings. 8vo. $3-5 
 
 BULLOCK. The Rudiments of Architecture and Building: 
 For the use of Architects, Builders, Draughtsmen, Machinists, En- 
 gineers and Mechanics. Edited by JOHN BULLOCK, author of " The 
 American Cottage Builder." Illustrated by 250 Engravings. 8vo. $3.50 
 
 BURGH. Practical Rules for the Proportions of Modern 
 
 Engines and Boilers for Land and Marine Purposes. 
 By N. P. BURGH, Engineer. I2mo. .... $1.50 
 
 BYLES. Sophisms of Free Trade and Popular Political 
 
 Economy Examined. 
 
 By a BARRISTER (SiR JOHN BARNARD BYLES, Judge of Common 
 Pleas). From the Ninth English Edition, as published by the 
 Manchester Reciprocity Association. I2mo. . . . $1.25 
 
 BOWMAN. The Structure of the Wool Fibre in its Relation 
 
 to the Use of Wool for Technical Purposes : 
 Being the substance, with additions, of Five LectureSj delivered at 
 the request of the Council, to the members of the BradTord Technical 
 College, and the Society of Dyers and Coloiists. By F. II. BOW- 
 MAN, D. Sc., F. R. S. E., F. L. S. Illustrated by 32 engravings. 
 8vo $6.50 
 
 BYRNE. Hand-Book for the Artisan, Mechanic, and Engi- 
 neer: 
 
 Comprising the Grinding and Sharpening of Cutting Tools, Abva-.ve 
 Processes, Lapidary Work, Gem and Glass Engraving, Varnishing 
 and Lackering, Apparatus, Materials and Processes for Grinding and 
 
HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
 Polishing, etc. By OLIVER BYRNE. Illustrated by 185 wood en- 
 gravings. 8vo. 5.00 
 
 BYRNE. Pocket-Book for Railroad and Civil Engineers: 
 
 Containing New, Exact and Concise Methods for Laying out Railroad 
 Curves, Switches, Frog Angles and Crossings ; the Staking out of 
 work ; Levelling ; the Calculation of Cuttings ; Embankments ; Earth- 
 work, etc. By OLIVER BYRNE. i8mo., full bound, pocket-book 
 form $1-75 
 
 BYRNE. The Practical Metal- Worker's Assistant : 
 Comprising Metallurgic Chemistry; the Arts of Working all Metal* 
 and Alloys; Forging of Iron and Steel; Hardening and Tempering; 
 Melting and Mixing; Casting and Founding; Works in Sheet Metal; 
 the Processes Dependent on the Ductility of the Metals; Soldering; 
 and the most Improved Processes and Tools employed by Metal- 
 workers. With the Application of the Art of Electro-Metallurgy to 
 Manufacturing Processes ; collected from Original Sources, and from 
 the works of Holtzapffel, Bergeron, Leupold, Plumier, Napier, 
 Scoffern, Clay, Fairbairn and others. By OLIVER BYRNE. A new, 
 revised and improved edition, to which is added an Appendix, con- 
 taining The Manufacture of Russian Sheet-Iron. By JOHN PERCY, 
 M. D., F. R. S. The Manufacture of Malleable Iron Castings, and 
 Improvements in Bessemer Steel. By A. A. FESQUET, Chemist and 
 Engineer. With over Six Hundred Engravings, Illustrating every 
 Branch of the Subject. 8vo. - $5.00 
 
 BYRNE. The Practical Model Calculator: 
 
 For the Engineer, Mechanic, Manufacturer of Engine Work, Naval 
 Architect, Miner and Millwright. By OLIVER BYRNE. 8vo., nearly 
 600 pages $4-50 
 
 CABINET MAKER'S ALBUM OF FURNITURE: 
 Comprising a Collection of Designs for various Styles of Furniture. 
 Illustrated by Forty-eight Large and Beautifully Engraved Plates. 
 Oblong, 8vo #2.00 
 
 CALLINGHAM. Sign Writing and Glass Embossing: 
 
 A Complete Practical Illustrated Manual of the Art. By JAMES 
 CALLINGHAM. i2mo $1.50 
 
 CAMPIN. A Practical Treatise on Mechanical Engineering: 
 Comprising Metallurgy, Moulding, Casting, Forging, Tools, Work, 
 shop Machinery, Mechanical Manipulation, Manufacture of Steam* 
 Engines, etc. With an Appendix on the Analysis of Iron and Iron 
 Ores. By FPANCIS CAMPIN, C. E. To which are added, Observations 
 on the Construction of Steam Boilers, and Remarks upon Furnaces 
 used for Smoke Prevention ; with a Chapter on Explosions. By R. 
 ARMSTRONG, C. E., and JOHN BOURNE. Rules for Calculating th 
 Change Wheels for Screws on a Turning Lathe, and for a Wheel 
 cutting Machine. By J. LA NICCA. Management of Steel, Includ- 
 ing Forging, Hardening, Tempering, Annealing, Shrinking and 
 Expansion; and the Case-hardening of Iron. By G. EDE. 8vo. 
 Illustrated with twenty-nine plates and 100 wood engravings $$.QQ 
 
HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
 CAREY. A Memoir of Henry C. Carey. 
 
 By DR. WM. ELDER. With a portrait. 8vo., cloth . . 75 
 
 CAREY. The Works of Henry C. Carey : 
 
 Harmony of Interests : Agricultural, Manufacturing and Commer 
 
 cial. 8vo. $1.25 
 
 Manual of Social Science. Condensed from Carey's " Principles 
 of Social Science." By KATE McKEAN. I vol. I2mo. . $2.25 
 Miscellaneous Works. With a Portrait. 2 vols. 8vo. $10.00 
 
 Past, Present and Future. 8vo $2.50 
 
 Principles of Social Science. 3 volumes, 8vo. . . $7.50 
 The Slave-Trade, Domestic and Foreign; Why it Exists, and 
 How it may be Extinguished (1853). 8vo. . . , $2.00 
 The Unity of Law : As Exhibited in the Relations of Physical, 
 Social, Mental and Moral Science (1872). 8vo. . . $2.50 
 
 CLARK. Tramways, their Construction and Working : 
 
 Embracing a Comprehensive History of the System. With an ex' 
 haustive analysis of the various modes of traction, including horse- 
 power, steam, heated water and compressed air; a description of the 
 varieties of Rolling stock, and ample details of cost and working ex- 
 penses. By D. KINNEAR CLARK. Illustrated by over 200 wood 
 engravings, and thirteen folding plates. 2 vols. 8vo. . $12.50 
 
 COLBURN. The Locomotive Engine : 
 
 Including a Description of its Structure, Rules for Estimating its 
 Capabilities, and Practical Observations on its Construction and Man- 
 agement. By ZERAH COLBURN. Illustrated. I2mo. . $1.00 
 
 COLLENS. The Eden of Labor ; or, the Christian Utopia. 
 By T. WHARTON COLLENS, author of " Humanics," " The History 
 of Charity," etc. I2mo. Paper cover, $ I. oo; Cloth . $f.2j 
 
 COOLEY. A Complete Practical Treatise on Perfumery : 
 Being a Hand-book of Perfumes, Cosmetics and other Toilet Articles, 
 With a Comprehensive Collection of Formulae. By ARNOLD J 
 COOLEY. i2mo. . . . . . . . $1.50 
 
 COOPER. A Treatise on the use of Belting for tfie Trans 
 
 mission of Power. 
 
 With numerous illustrations of approved and actual methods of ar- 
 ranging Main Driving and Quarter Twist Belts, and of Belt Fasten 
 ings. Examples and Rules in great number for exhibiting and cal- 
 culating the size and driving power of Belts. Plain, Particular and 
 Practical Directions for the Treatment, Care and Management o' 
 Belts. Descriptions of many varieties of Beltings, together witn 
 chapters on the Transmission of Power by Ropes ; by Iron and 
 Wood Frictional Gearing; on the Strength of Belting Leather; and 
 on the Experimental Investigations of Morin, Briggs, and others. Bj 
 JOHN H. COOPER, M. E. 8vo $3.50 
 
 CRAIK. The Practical American Millwright and M'Uer. 
 
 By DAVID CRAIK, Millwright. Illustrated by numerous wood eiv 
 gravings and two folding plates. 8vo. . . . $3. 50 
 
HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
 CREW. A Practical Treatise on Petroleum : 
 
 Comprising its Origin, Geology, Geographical Distribution, History, 
 Chemistry, Mining, Technology, Uses and Transportation. Together 
 with a Description of Gas Wells, the Application of Gas as Fuel, etc. 
 By BENJAMIN J. CREW. With an Appendix on the Product and 
 Exhaustion of the Oil Regions, and the Geology of Natural Gas in 
 Pennsylvania and New York. By CHARLES A. ASHBURNER, M. S., 
 Geologist in Charge Pennsylvania Survey, Philadelphia Illustrated 
 by 70 engravings. 8vo. 508 pages . . . . $<J.oo 
 
 CROSS. The Cotton Yarn Spinner: 
 
 Showing how the Preparation should be arranged for Different 
 Counts of Yarns by a System more uniform than has hitherto been 
 practiced; by having a Standard Schedule from which we make all 
 our Changes. By RICHARD CROSS. 122 pp. I2mo. . 75 
 
 CRISTIANI. A Technical Treatise on Soap and Candles: 
 With a Glance at the Industry of Fats and Oils. By R. S. CRIS 
 TIANI, Chemist. Author of " Perfumery and Kindred Arts." Illus- 
 trated by 176 engravings. 581 pages, 8vo. . . . $15.00 
 
 CRISTIANI. Perfumery and Kindred Arts: 
 
 A Comprehensive Treatise on Perfumery, containing a History of 
 Perfumes from the remotest ages to the present time. A complete 
 detailed description of the various Materials and Apparatus used in 
 the Perfumer's Art, with thorough Praciical Instruction and carefui 
 Formulae, and advice for the fabrication of all known preparations of 
 the day, including Essences, Tinctures, Extracts, Spirits, Waters, 
 Vinegars, Pomades, Powders, Paints, Oils, Emulsions, Cosmetics, 
 Infusions, Pastilles, Tooth Powders and Washes, Cachous, Hair Dyes, 
 Sachets, Essential Oils, Flavoring Extracts, etc.: ar 'd full details for 
 making and manipulating Fancy Toilet Soaps, Shaving Creams, etc., 
 by new and improved methods. With an Appendix giving hints and 
 advice for making and fermenting Domestic Wines, Cordials, Liquors, 
 Candies, Jellies, Syrups, Colors, etc., and for Perfuming and Flavor- 
 ing Segars, Snuff and Tobacco, and Miscellaneous Receipts fot 
 various useful Analogous Articles. By R. S. CRISTIANI, Con- 
 sulting Chemist and Perfumer, Philadelphia. 8vo. . . $10.00 
 
 DAVIDSON. A Practical Manual of House Painting, Grain- 
 ing, Marbling, and Sign- Writing: 
 
 Containing full information on the processes of House Painting in 
 Oil and Distemper, the Formation of Letters and Practice of Sign- 
 Writing, the Principles of Decorative Art, a Course of Elementary 
 Drawing for House Painters, Writers, etc., and a Collection of Useful 
 Receipts. With nine colored illustrations of Wouds and Marbles, 
 and numerous wood engravings. By ELLIS A. DAVIDSON. I2mo. 
 
 #3-00 
 
 DAVIES. A Treatise on Earthy and Other Minerals and 
 
 Mining : 
 
 By D. C. DAVIES, F. G. S., Mining Engineer, etc.. Iliustrated b) 
 76 Engravings. I2mo $S- 
 
HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
 DAVIES. A Treatise on Metalliferous Minerals and Mining: 
 By D. C. DAVIES, F. G. S.. Mining Engineer, Examiner of Mines, 
 Quarries and Collieries. Illustrated by 148 engravings of Geological 
 Formations, Mining Operations and Machinery, drawn from tht 
 practice of all parts of the world. 2d Edition, I2mo., 450 pages $5.00 
 
 DAVIES. A Treatise on Slate and Slate Quarrying: 
 
 Scientific, Practical and Commercial. By D. C. DAVIES, F. G. S., 
 Mining Engineer, etc. With numerous illustrations and foldin 
 plates. 
 
 DAVIS. A Treatise on Steam-Boiler Incrustation and Meth- 
 
 ods for Preventing Corrosion and the Formation of Scale . 
 By CHARLES T. DAVIS. Illustrated by 65 engravings. 8vo. $1.50 
 DAVIS. The Manufacture of Paper: 
 
 Being a Description of the various Processes for the Fabrication, 
 Coloring and Finishing of every kind of Paper, Including the Dif- 
 ferent Raw Materials and the Methods for Determining their Values, 
 the Tools, Machines and Practical Details connected with an intelli- 
 gent and a profitable prosecution of the art, with special reference to 
 the best American Practice. To which are added a History of Pa- 
 per, complete Lists of Paper-Making Materials, List of American 
 Machines, Tools and Processes used in treating the Raw Materials, 
 and in Making, Coloring and Finishing Paper. By CHARLES T. 
 DAVIS. Illustrated by 156 engravings. 608 pages, 8vo. $6.00 
 
 DAVIS. The Manufacture of Leather: 
 
 Being a description of all of the Processes for the Tanning, Tawing, 
 
 Currying, Finishing and Dyeing of every kind of Leather ; including 
 
 the various Raw Materials and the Methods for Determining their 
 
 Values; the Tools, Machines, and all Details of Importance con- 
 
 nected with an Intelligent an-d Profitable Prosecution of the Art, with 
 
 Special Reference to the Best American Practice. To which are 
 
 added Complete Lists of all American Patents for Materials, Pro- 
 
 cesses, Tools, and Machines for Tanning, Currying, etc. By CHARLES 
 
 THOMAS DAVIS. Illustrated by 302 engravings and 12 Samples of 
 
 Dyed Leathers. One vol., 8vo., 824 pages . . , , $10.00 
 
 DAWIDOWSKY BRANNT. A Practical Treatise on the 
 
 Raw Materials and Fabrication of Glue, Gelatine, Gelatine 
 
 Veneers and Foils, Isinglass, Cements, Pastes, Mucilages, 
 
 etc. : 
 
 Eased upon Actual Experience. By F. DAWIDOWSKY, Technical 
 Chemist. Translated from the German, with extensive additions, 
 including a description of the most Recent American Processes, by 
 WILLIAM T. BRANNT, Graduate of the Royal Agricultural College 
 of Eldena, Prussia. 35 Engravings. I2mo. . . . $2.50 
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HENRY CAREY BA.IRD & CO.'S CATALOGUE. ti 
 
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12 HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
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J4 HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
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 GRISWOLD. Railroad Engineer's Pocket Companion for ths 
 
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 GRUNER. Studies of Blast Furnace Phenomena: 
 
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HENRY CAREY BAIRD & CO.'S CATALOGUE. 15 
 
 HAUPT RHAWN. A Move for Better Roads : 
 
 Essays on Road-making and Maintenance and Road Laws, for 
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16 HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
 *. 
 
 KENTISH. A Treatise on a Box of Instruments, 
 
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 KICK. Flour Manufacture . 
 
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 imperial German Polytechnic Institute, Prague. Translated from 
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 KINGZETT. The History, Products, and Processes of the 
 
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 Including the most Recent Improvements. By CHARLES THOMAS 
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 LANGBEIN. A Complete Treatise on the Electro-Deposition 
 
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 LARDNER. The Steam-Engine : 
 
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HENRY CARE\ BAIRD & CO.'S CATALOGUE. 17 
 
 LARKIN. The Practical Brass and Iron Founder's Guide: 
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 their Alloys, etc.; to which are added Recent Improvements in tht 
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 JAMES LARKIN, late Conductor of the Brass Foundry Department U 
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 LEROUX. A Practical Treatise on the Manufacture of 
 
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 LEFFEL. The Construction of Mill-Dams : 
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 LESLIE. Complete Cookery: 
 
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 Lockwood's Dictionary of Terms : 
 
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i8 HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
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 MAIN and BROWN. Questions on Subjects Connected with 
 
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 and THOMAS BROWN, Chief Engineer, R. N. I2mo., cloth . $1,00 
 
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HENRY CAREY BAIRD & CO/S CATALOGUE. 19 
 
 MOORE. The Universal Assistant and the Complete Me- 
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 Containing over one million Industrial Facts, Calculations, Receipts, 
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 MORRIS. Easy Rules for the Measurement of Earthworks; 
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 MORTON. The System of Calculating Diameter, Circumfer- 
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 Together with Interest and Miscellaneous Tables, and other informa- 
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 NAPIER. Manual of Electro- Metallurgy : 
 
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 By JAMES NAPIER. Fourth American, from the Fourth London 
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 NAPIER. A System of Chemistry Applied to Dyeing. 
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 NEVILLE. Hydraulic Tables, Coefficients, and Formulae, foi 
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 Third Edition, with Additions, consisting of New Formulae for the 
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20 HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
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 NICHOLSON. A Manual of the Art of Bookbinding : 
 
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HENRY CAREY BAIRD & CO.'S CATALOGUE. 21 
 
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22 HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
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HENRY CAREY BAIRD & CO.'S CATALOGUE. 23 
 
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24 HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
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26 HENRY CAREY BAIRu & CO.'S CATALOGUE. 
 
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