Salt and the salt industry E-Book

Albert Frederick Calvert

• Herausgeber: Science & Technology Publishing
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 190

Veröffentlichungsjahr: 2025

Beschreibung

Salt and the Salt Industry is a comprehensive exploration of one of humanity’s most essential and ancient commodities. This detailed volume delves into the history, science, and economic significance of salt, tracing its journey from prehistoric times to its pivotal role in modern industry. The book examines the geological formation of salt deposits, the various methods of extraction—including mining, evaporation, and solution processes—and the technological advancements that have shaped the industry over centuries. Through vivid descriptions and meticulous research, the author highlights the cultural and historical importance of salt, illustrating how it has influenced trade routes, economies, and even the rise and fall of civilizations. The narrative covers the development of salt works in different regions, the evolution of salt laws and monopolies, and the impact of salt taxation on societies. Readers are introduced to the lives of workers in salt mines and salt pans, the challenges they faced, and the innovations that improved their working conditions. The book also addresses the diverse uses of salt beyond the table, from food preservation and animal husbandry to its critical applications in chemical manufacturing and other industries. Detailed illustrations and diagrams enrich the text, providing insight into the machinery, tools, and processes used throughout history. Salt and the Salt Industry is not only a technical treatise but also a social and economic history, offering readers a fascinating look at how this humble mineral has shaped human civilization. Whether you are interested in industrial history, chemistry, or the broader story of human ingenuity, this book provides a thorough and engaging account of salt’s enduring legacy.

Leseprobe

Cover

Transcriber’s Note

Larger versions of most illustrations may be seen by right-clicking them and selecting an option to view them separately, or by double-tapping and/or stretching them.

VIEW OF THE COMMERCIAL SALT COMPANY’S BRINE RESERVOIRS AT RODE HEATH, CHESHIRE,

Showing the Brine being pumped up from a depth of 250 feet

Frontispiece

PITMAN’S COMMON COMMODITIES AND INDUSTRIES

SALTAND THE SALT INDUSTRY

BYALBERT F. CALVERT, F.C.S.AUTHOR OF “SALT IN CHESHIRE”; “THE SALT DEPOSITS OF THE WORLD”; ETC.

LondonSir Isaac Pitman & Sons, Ltd., 1 Amen Corner, E.C.4Bath, Melbourne and New York

Printed by Sir Isaac Pitman & Sons, Ltd., London, Bath, Melbourne and New York

PREFACE

The fact that salt is almost universally distributed over the surface of the globe, and has been worked in a number of countries from time immemorial, will explain the impossibility, in the limited space at my disposal, to consider the mineral and its manufacture comprehensively as the staple of a world-industry. The salt deposits of China, India, Russia, Japan, and Austria would each require a volume of the size of this if the subject was to be even adequately represented. I have, therefore, dared to assume that the public will accept a book practically restricted to one phase of the matter, and allow me to concentrate upon our Cheshire salt district and its industry.

Caesar’s salinators, who found the natives of Cheshire procuring brine from little natural springs in the neighbourhoods of Northwich and Nantwich, taught them to boil the brine and precipitate the salt crystals in open pans set over open fires, and in the following 1,700 years all the salt of Cheshire was manufactured by that process. With the discovery of rock salt in 1670, mining was introduced, and for another 200 years both rock salt and brine salt were produced. But from causes which I have described, the mines collapsed in rapid succession from about the middle of the nineteenth century, and fresh water breaking into the abandoned workings converted them into the brine reservoirs from which the salt-men have since obtained their inexhaustible supplies of brine.

But, although the salt industry is one of the oldest in the country, it has received scant treatment at the hands of authors, and this is accounted for by the fact that the trade has been conducted by a comparatively small group of men who have resisted all attempts of outsiders to participate in either their secrets or their profits. The desire for information has been consistently rebuked, and practical details relating to borings, working expenses, levels of brine, and quantities raised have been jealously concealed. It was my good fortune to be able to prosecute most of my researches on the spot, and to supplement the knowledge gained from books, pamphlets, scientific papers and periodicals, with material contained in private records and documents placed at my disposal, and information obtained by word of mouth.

There is romance in every industry, and a modicum of it enters into the development of the Cheshire salt trade; but for the most part the story is a chronicle of bitter struggles to maintain a monopoly, of money thrown away, of produce sold at ruinous loss, of obsolete methods stubbornly persisted with, and of hardship and injustice callously inflicted—in a word, of the sordid determination of the salt magnates to crush competition and control prices. The methods of the Dark Ages survived both in the manufacture and the marketing of the produce, and the industry has more than once been reduced almost to ruin through the war of extermination in which for so many years the salt-men were engaged. It is not a pretty story, but it is one of unusual interest; and I have endeavoured in the telling of it to retain the interest and preserve the essential facts.

ALBERT F. CALVERT.

Royston,Eton Avenue, N. W.

CONTENTS

CHAP.

PAGE

PREFACE

iii

I.

THE CHEMISTRY AND PROPERTIES OF SALT

1

II.

THE BEGINNINGS OF THE SALT INDUSTRY

8

III.

THE CHESHIRE WICHES

32

IV.

DEVELOPMENT OF BRINE PROCESSES

56

V.

FORMATION AND EXTENT OF THE CHESHIRE DEPOSITS

83

VI.

THE CHESHIRE SUBSIDENCES

97

VII.

LATEST METHODS OF SALT-MAKING

125

VIII.

THE SALT MARKET

142

ILLUSTRATIONS

PAGE

VIEW OF THE COMMERCIAL SALT COMPANY’S BRINE RESERVOIRS AT RODE HEATH, CHESHIRE

Frontispiece

ANCIENT SALT WORKS

13

ANCIENT SALT WORKS

19

WIELIEZKA SALT MINES

21

SLANICU, RUMANIA, INTERIOR OF SALT MINE

25

WIELIEZKA SALT MINES

29

SUBSIDENCE OF LAND, NORTHWICH

41

DUNKIRK SUBSIDENCE, NORTHWICH

49

THE CANAL-BURST AND LANDSLIP NEAR NORTHWICH IN 1907

59

A SALT STORE-SHED

67

WITTON BROOK, SUBMERGENCE OF AGRICULTURAL LAND

75

WORKING IN DANGEROUS GROUND AFTER SUBSIDENCE, DUNKIRK LAKE, NORTHWICH

81

STREET-RAISING IN PROGRESS—HIGH STREET, NORTHWICH

89

THIS ROAD WAS RAISED TWENTY FEET IN TWENTY YEARS. NONE OF THESE BUILDINGS IS NOW STANDING—NORTHWICH

93

INTERIOR PENNY’S LANE MINE, NORTHWICH

99

REMARKABLE SUBSIDENCE IN NORTHWICH

111

A ROW OF OPEN PANS

119

ILLUSTRATION OF FOUR SCOTT PATENT DOUBLE EFFECT SALT EVAPORATORS, WITH AUTOMATIC SALT DISCHARGERS, SALT CONVEYORS, AND HYDRO-EXTRACTORS

131

THE HODGKINSON PATENT SALT-MAKING PLANT

137

SALT AND THE SALT INDUSTRY

CHAPTER ITHE CHEMISTRY AND PROPERTIES OF SALT

“Salt” was the name which was given in the first place to the residue left by the evaporation of sea-water, but the designation was subsequently employed to include the other substances held in solution in the sea, and, at a still later period, the name was still further extended by chemists to cover all the combinations of a base and an acid which are now classed as “salts.” Sodium, or sodic chloride Na Cl, which is now distinguished as “common salt,” is an example of the simplest type of chemical salt, its molecule consisting of one atom of the metal sodium combined with one atom of the gas chlorine, both sodium and chlorine being mono-valent elements, i.e., one atom of each being able to unite with, or displace from a compound, one atom of hydrogen.

Rock-salt is rarely found in an absolutely pure anhydrous state, in which it is colourless and perfectly transparent. In most rock-salt mines such specimens are regarded as curiosities, but in the deposits of Nevada and of Wieliezka, in Hungary (where the salt, containing 100 per cent. NaCl, is the purest in the world), large masses of quite transparent salt are encountered. The white opaque mass which the ordinary person is accustomed to think of as rock-salt, is the purified product of commerce. The colour of sea-water is affected by its percentage of salt, the colour changing from blue to green as the quantity of salt decreases; but sea-salt is generally white, although not transparent owing to the presence of minute particles of water, air, etc., in its intercrystalline spaces. But rock-salt is never more than whitish inclining to grey, and, as a general rule, it is coloured by earth or mineral impurities. The Salt Range in the Panjab yields a substance that varies from pink to red, according to the different quantities of iron present as impurities. That found at Marston, in Cheshire, varies from yellow to red and brownish-red in colour. Small blocks of transparent salt of a deep sapphire blue are occasionally found in the Wieliezka mines. The colour disappears on heating, and when the salt is ground to powder. It is attributed by some chemists to the presence of subchloride of sodium, by others to the presence of thin cavities having parallel surfaces with gas inclusions.

Common salt, which is classed as “sweet” to distinguish it from the bitter-tasting salts of magnesium, has a peculiar saline taste which gains in pungency with refinement, and in its pure state is odourless. In solution, the smallest quantity perceptible to the taste is about 15 grains to the litre, roughly, 68 grains to the gallon.

Common salt is highly soluble in cold water, and rather more so in hot water, but while it dissolves slightly in alcohol, neither ether nor oil has any effect upon it. One hundred parts of distilled water at 60° F. (15·5° C.) will dissolve 35·9 parts of chemically pure NaCl. A saturated solution of common salt, therefore, contains 26·42 per cent. NaCl. The increase of solubility of NaCl in proportion to the rise in temperature, calculated by Gay Lussac and Poggiale, is particularly marked between 100 deg. and 110 deg., when boiling point is passed, the increase amounting to ·74 parts of 10 deg., as compared with an increase of one 1·09 parts between freezing and boiling points. In a double solution of NaCl and some other more soluble salt, as sodium or magnesium sulphate or magnesium chloride, the solubility of sodium chloride is very greatly reduced.

The evaporation of brine is slightly less rapid than that of ordinary pure water, and the boiling point of brine varies with the amount of NaCl present in solution, from 100·21 deg. when only 1 per cent. NaCl is present, to 108·99 deg. when the solution contains 29·4 per cent. of NaCl. A saturated solution of refined table-salt (i.e., a solution containing 26·4 per cent. NaCl) has, at normal temperatures, specific gravity 1·2. Salt crystals have specific gravity 2·167 at a temperature of 17°. The salt which separates at high temperature contains no water of crystallization. But when the thermometer falls much below -15° C. the crystals have the composition NaCl.2H₂O and are prismatic in shape. When heated, these give up their water of crystallization and take the simple composition NaCl.

Pure sodium chloride is not deliquescent (i.e., it does not dissolve and become liquid by absorbing moisture from the air), but, owing to the presence of minute quantities of magnesium chloride (one of the most deliquescent substances known), all except the most refined table-salt appears to be so to a slight extent. Even the finest table-salt is slightly hygroscopic, its crystals absorbing as much as ·6 per cent. moisture from a damp atmosphere. In some of the mines of Cheshire and Austria the very fine saline dust that is diffused through the atmosphere is found by the miners to be extremely irritating to the eyes and lungs, but all the more usual kinds of salt are sufficiently hygroscopic to indicate plainly the condition of the atmosphere.

Sodic chloride melts at a very high temperature, and at a still higher temperature it evaporates, while at white heat it forms thick clouds.

It would be supposed that in the same ocean areas, the proportion of the salt contents, except where marked differences in temperature occur, would be fairly constant, but it has been demonstrated that, even where masses of water of varying densities are superimposed upon each other, no very complete process of diffusion takes place between them, and practical salt-makers are familiar with differences in density which occur in different parts of the same salt pan.

The hardness of a mineral depends upon the degree of cohesion of its particles; but although no unit of hardness has been determined upon, and therefore no accurate method of measuring hardness has been arrived at, minerals have been approximately classed in a comparative table of ten substances, of which talc is placed at one end and diamond at the other. In this table, rock salt appears in the second place, and its hardness is estimated at 2·5. Its cohesion or power of supporting pressure is, therefore, about twice as great as that of bricks, and the practical advantage of this property is fully employed in rock-salt mines, where galleries and roofs are supported upon pillars of salt.

Common salt is a crystalline substance which crystallizes in the Isometric, Monometric, or Tesseral system. That is to say, each crystal has three equal perpendicular planes of symmetry and six equal diagonal planes of symmetry. The crystals generally form cubes having six rectangular and equilateral faces. When these form on the surface of brine the sides often collapse, giving the distinctive “hopper-shaped” forms. More rarely the crystals form in octahedra, having eight equal, equilateral triangular faces, or in long needles under certain modifying conditions.

The hollow quadrangular pyramidal form with an irregular inner surface arranged in steps, which manufactured salt generally takes, is the result of continuous depositions of crystals from a constantly saturated solution of brine during a considerable period, being superimposed layer after layer upon each other.

In his exhaustive explanation of these phenomena, given in his Principles of Chemistry, Mendeléeff says: “If a solution of sodium chloride be slowly heated from above, where the evaporation takes place, the upper layer will become saturated before the lower and cooler layers, and therefore crystallization will begin on the surface, and the crystals first formed will float—having also dried from above—on the surface until they become quite soaked. Being heavier than the solution the crystals are partially immersed in it, and the following crystallization, also proceeding on the surface, will only form crystals by the side of the original crystals. A funnel is formed in this manner. It will be borne on the surface like a boat (if the liquid be quiescent) because it will grow more from the upper edges. We can thus understand this, at first sight, strange funnel-form of crystallized salt. To explain why the crystallization under the above conditions begins at the surface and not at the lower edges, it must be mentioned that the specific gravity of a crystal of sodium chloride is 2·16, and that a solution saturated at 25° contains 26·7 per cent. of salt and has a specific gravity 1·2004 at 25°; at 15° a saturated solution contains 26·5 per cent. of salt and has a specific gravity 1·203 at 15°. Hence, a solution saturated at a higher temperature is specifically lighter, notwithstanding the greater amount of salt it contains. With many substances, surface crystallization cannot take place, because their solubility increases more rapidly with the temperature than their specific gravity decreases. In this case the saturated solution will always be in the lower layers, where also the crystallization will take place.”

The acoustic properties of common salt render it an excellent medium for the transmission of sound, and as it possesses in a high degree the power of staying decomposition in dead organisms, it is, perhaps, the commonest of all preservatives. It is largely owing to its preservative property that common salt is an absolute necessity to the life of man and the higher animals, from a quarter to half an ounce a day being sufficient to prevent the putrefaction of food in the digestive tract in the case of an adult. In agriculture, salt is not only valuable as a destroyer of weeds and insect life, but used sparingly and with knowledge, it forms an excellent manure; while its more strictly chemical value in the manufacture of soda, chlorine, etc., causes it to play an important part in many branches of industry.

Even at the highest temperatures, heat cannot effect the decomposition of common salt. At a red heat, pure sodic chloride melts and becomes liquid, and if cooled again, a solid crystalline mass is formed. Ordinary salt fuses at a lower temperature and volatilizes when heated in an open vessel. But even in a closed vessel the purest salt will volatilize at a white heat. When gases or fluids are present in the crystalline cavities, heat causes decrepitation.

On the subject of the composition of brine, it is only necessary to add that it is so extremely variable that no two districts produce brine springs of the same strength and density, while the composition of ocean brine varies not only from ocean to ocean, but also for different parts and different depths in the same plane of water, and with the different distances from the mouths of large rivers. In the Cheshire district, the Brine test or Salinometer is graduated to show ounces in the gallon; but the gallon is the old Winchester Gallon of 231 cub. in. and not the Imperial Gallon of 277·274 cub. in. These are related to each other in the proportion of 10 to 12, therefore the Imperial Gallon will contain ⅕ more than the old gallon. Fully saturated brine by the Salinometer contains 42 oz. (2 lb. 10 oz.), therefore, in the Imperial Gallon 50·4 oz. As brines vary from 2 lb. 8 oz., or 40 oz. old measure, or 3 lb. or 48 oz. Imperial to 2 lb. 10 oz., or 3 lb. 2 oz. Imperial, so 1,000 gallons, which has been chosen as the measure for assessing brine-pumpers—under the Brine Pumping Compensation for Subsidence Act of 1891—will contain under the old measurement 2,625 lb. and under the Imperial 3,125 lb. of salt.

CHAPTER IITHE BEGINNINGS OF THE SALT INDUSTRY

Salt, being existent in all animal and vegetable life, is coeval with life itself; it was present in the first herbage which gave nourishment to the first beast that, in its turn, became food for the first omnivorous man. In the beginning, man consumed the saline essences that were required to preserve his body in health, in the form of sodium chloride, which he absorbed in the uncooked flesh of animals, birds, and fishes, and in raw green-foods. The herbivorous animals were equally dependent upon salt, and, finding it in only infinitesimal quantities in the grasses upon which they fed, instinct directed them to the sea swamp pasturage and to the outcropping salt deposits. So long as man’s diet consisted of uncooked foods, his fresh meat provided him with a sufficiency of salt, but directly he employed a cook-pot in the preparation of his food, the boiling processes denuded it of 70 per cent. of its natural salt, and it became necessary for him to make up the deficiency. It must have been at this period that his herds directed his attention to the “salt licks” from which they satisfied their own saline wants, and enabled him to secure salt as a distinct and separate condiment.

It is probable that, from the Palaeolithic Age down to the time of the early Roman writers, man was content to season his victuals by the simple process of licking a piece of rock-salt, and we have no record to indicate the period when salt was first employed in the cooking of food. From varieties of grain and fragments of pottery that have been discovered in the dwellings of the cave-men of Belgium, it is supposed that salt was employed in the cooking of wheat and barley some five thousand years ago. Thirteen centuries before Christ, fish preserved in salt was eaten in Ancient Troy, and, according to Herodotus, the Egyptians not only salted ducks, quails, and a species of sardine which inhabited the Nile, but also employed salt or brine as an antiseptic in preparing the bodies of the illustrious dead for the process of embalming.

We cannot determine the period in which salt came to be regarded as a symbol of sanctity or entered into the religious ceremonials of the ancients. We know that in the Levitical Law, promulgated in 1500 B.C., every meat-offering was seasoned with salt, and salt is referred to in the “Verbal Instructions” which were enunciated by the founder of Buddhism, five centuries later. By the time of Pythagoras, about 600 B.C., salt was regarded as the emblem of justice, but who shall say when the Arabs first employed it as a token of friendship, or the Chinese offered their first oblation to Phelo, the salt deity of Celestial worship? We read in Herodotus that caravans brought salt from North Africa, and Schleiden tells us that the priests of Egypt preferred the salt of Hammomen to that evaporated from sea-water; but these references do not help us to fix the date when salt became an article of commerce, or tell us when or where or by whom it was first produced in a manufactured form. It was rock-salt which the Egyptians procured from the salt basin of the Sahara, and rock-salt from the margin of the Red Sea was the variety that is referred to by the compilers of Biblical history. But, although the natural crude product was probably the sole form in which it was known in the Western world by the Ancients, and through the vaunted golden epochs of Babylon, Byzantium, and Greece, the Chinese—who had invented explosives before the Romans had perfected the catapult, and had learnt to navigate by the compass while yet the mariners of the Mediterranean were dependent upon the stars and their wits—had probably been familiar for ages with a salt manufactured by a process, the origin of which they had forgotten, but the practice of which was to remain in operation, almost without revision, for further thousands of years.

The first mention of salt in the Chinese language is found in the annals of the Emperor Yu (2205–2197 B.C.), who ordered the province of Shantung to supply the Court with that commodity. During the Chow dynasty (1122–249 B.C.) the administration of the salt industry was conducted by Court officials, but the Crown monopoly of salt was not instituted until the days of Kuan Chung, who died 645 B.C. Between A.D. 561 and A.D. 583, references to various taxes on salt lead us to the conclusion that salt was produced at that period from sea-water, salt marshes, and salt springs, and at the present day salt is produced in China in three varieties—sea-salt, lake-salt, and well-salt. As the success of the boiling operation (which antedated by unnumbered centuries the comparatively modern industry of extracting salt from sea-water by evaporation in the sun) depends mainly on the condition of the brine and the time allowed in each stage of the process, the details were the subject of many series of experiments in the pursuit of the perfect system, but since about the twelfth century the following method has been consistently followed by the Chinese salt-makers. The whole of the sea-shore in the neighbourhood of the salt works is measured out and divided into a number of small, regular squares; the surface layer in each is dug out; the bottom of each pit thus formed is then strewn with straw, and the earth that has been removed is thrown back upon it. When these brine ovens, as they were called—which are shaped like chests, 9 ft. long, 2 ft. broad, and 3 ft. deep—are prepared, they are soaked with sea-water. The sea-water in the interior of the ovens forms brine, and flows through little ditches into wells which have been dug for its reception. From these wells, which are about 8 ft. deep, the brine is drawn out and carried to the boiling ovens. These brine ovens are furnished with large evaporating pans, three to five of which are attached to each oven. The boiling takes place at once and is continued without interruption, from 11 p.m. until 10.30 on the following morning, and during this period the salt is taken out six times. As soon as the salt begins to harden, pods of the tsao-chio tree are thrown into the pans, in order that the particles of salt may combine more quickly, and as soon as it is precipitated, it is removed and the pans are refilled with fresh brine. On an average, 600 cathés of the best brine yield 140 cathés of pure salt, which is produced in three qualities and colours—white, dark, and yellow. The white is the best, the dark is less esteemed, and the yellow, which is much inferior, has a bitter taste.

Since the fifteenth century, the Chinese have produced salt by solar evaporation of salt water, according to a simple but satisfactory process. Pits are dug on the sea-shore and bamboos are laid crosswise over them. The whole is covered with double mats, and sand is strewn over the top. Every morning and evening the covering of sand is soaked with sea-water by the tide, and the salt liquor finds its way into the pits. As soon as the water has receded, the salt workers appear with flaming bundles of straw, to test the saline character of the moisture, which is not regarded as fully impregnated unless the salt vapour arising from the pits extinguishes the fire. The brine thus produced is drawn off and run into secondary or crystallizing ponds, the level of which is set a foot or so below the first series of pits. The secondary ponds, which are smaller and of less depth, are provided with carefully-rolled, hard clay bottoms. When a sufficiently thick crystalline deposit has been formed at the bottom of the secondary ponds, workmen, starting at the centre, scrape the bottoms, working outward spirally and finishing at the corner of the pond, where the coarse crystalline product is collected and allowed to drain. When drained and dried, the salt is ready for transfer to the market.