PART ONE: MATERIALS 222 Progress) patented the making of sulphuric acid by burning sulphur and saltpetre in the necks of large glass globes containing a little water. That was converted to sulphuric acid, concentrated by distilling it. The price fell from £2 to 2s a pound, but the fragile nature of glass limited the scale of the process. Largescale manufacture only became possible when John Roebuck substituted lead chambers’, consisting of sheets of lead mounted on wooden frames, lead being both cheap and resistant to the acid. Roebuck, a student of chemistry at Leyden and Edinburgh set up his lead-chamber process outside the latter in secrecy, a condition that lasted as long as it usually does. Knowledge of the process spread rapidly; France had its first lead-chamber factory at Rouen around 1766. The process was improved and enlarged in scale; Roebuck’s chambers had a capacity of 200ft 3 (5.66m 3 ) but by 1860 Muspratt had achieved one of 56,000ft 3 (1584.8m 3 ). The rise in scale of course lowered the price; by 1830 it was 2 1/2d a pound. The first stage of the Leblanc process produced large quantities of hydrochloric acid gas, both poisonous and destructive. Not for the first or last time, the chemical industry made itself unpopular by its unfortunate environmental effects. In this case, from 1836 the gas began to be absorbed by a descending stream of water. The Alkali Act of 1863 required manufacturers to absorb at least 95 per cent of the acid. Important as the Leblanc process was, it had other drawbacks, principally the problem of disposing of the unpleasant ‘galligu’ or residue after the soda had been extracted. This led to a long search for an alternative and the gradual emergence of the ammonia-soda process, which eventually achieved success at the hands of the Belgian brothers Ernest and Alfred Solvay, with a patent in 1861 and satisfactory working four years later. It was introduced into Britain in 1872 by Ludwig Mond, who set up a works at Winnington in Cheshire in partnership with John Brunner which was to become part of Imperial Chemical Industries. Improvements were also made in the utilization of the hydrochloric acid formed in the Leblanc process. Henry Deacon oxidized it to chlorine using a catalyst (a substance that facilitates a reaction but can be removed unchanged at the end of the reaction). Also, Walter Weldon introduced the successful oxidation to chlorine using manganese dioxide, which enabled the output of bleaching powder to be quadrupled, with a considerable reduction in price. A new method of producing sulphuric acid had been suggested in 1831, by oxidizing sulphur dioxide to the trioxide using a platinum catalyst, but the platinum was found to be affected or ‘poisoned’ by the reaction and progress came to a halt. There was then little incentive to solve the problem, until the new organic chemical industry in the 1860s began to make demands for not only more but stronger sulphuric acid. So far, the only source of oleum, a form of strong sulphuric acid with an excess of sulphur trioxide, had been Nordhausen in Saxony, where it had been produced in limited quantities since the late seventeenth century. The contact process, as it came to be called, was THE CHEMICAL AND ALLIED INDUSTRIES 223 revived and at the hands of the German Rudolf Messel became, from around 1870, a practical proposition. The Badische Anilin- und Soda-Fabrik (BASF) was very active in pursuing research into this process. Various catalysts were tried, but from 1915 BASF used vanadium pentoxide and potash, and this became the most widely used material. Explosives Another important branch of the chemical industry was the manufacture of explosives (see Chapter 21). Until the middle of the nineteenth century, the only important explosive was gunpowder, but in the 1840s two other substances were noted. Schönbein found that the action of nitric acid on cellulose produced an inflammable and explosive substance and with John Hall at Faversham began to make gun-cotton, so called because cotton was the source of cellulose. In the same year nitroglycerine was discovered, formed by the action of nitric acid on glycerine, a product of soap manufacture. But these two substances were found to be too explosive to make or use. Alfred Nobel, however, showed that nitroglycerine could be made by absorbing it on kieselguhr, a kind of clay; in this form it was called dynamite. It was found that it would explode violently when touched off by a mercury fulminate detonator. In 1875, Nobel invented blasting gelatine, consisting of nitroglycerine with a small quantity of collodion cotton. The first application of these materials was in blasting in mines and quarries; their use in munitions became important in the 1880s. Fertilizers A less destructive application of the chemical industry was the manufacture of fertilizers. Apart from carbon, hydrogen and oxygen, there are three elements needed in relatively large quantities for plant nutrition: nitrogen, phosphorus and potassium. Until the end of the nineteenth century, the most important source of nitrogen was natural organic materials, but mineral sources were also important. Of these, by far the most significant were the sodium nitrate deposits in Chile, providing some 70 per cent of the world supply. By the 1960s this figure had shrunk to 1–2 per cent. The reason for the decline was the successful tapping of the richest source of nitrogen of all: the air we breathe. The ‘fixation’, or chemical combination, of nitrogen was known to be chemically feasible by the end of the eighteenth century and from around 1900 several processes had been developed on an industrial scale. But by far the most important of these was that worked out by Fritz Haber. It consisted of the synthesis of ammonia from its two constituent elements, nitrogen and hydrogen. The reaction had been studied spasmodically for many years but it was Haber who transformed it into an PART ONE: MATERIALS 224 industrial proposition. High pressures were at first avoided, but Haber found during his researches from 1907 to 1910 that a pressure of 200 atmospheres produced the highest yield. At that stage BASF once again entered the scene and engaged in research to find the most suitable catalyst. In 1913 the first full-scale plant for the synthesis of ammonia by the Haber process was built at Oppau, with a second at Leuna, near Leipzig three years later. By 1918, the process contributed half of Germany’s output of nitrogen compounds. Hostilities with Germany hindered the spread of knowledge of the process and it was only in the 1920s that manufacturing plants were set up in other leading industrial countries. Progress was then rapid and by 1950 fourfifths of nitrogen fixation was by this process. The catalyst most widely used from 1930 was finely divided iron mixed with various oxides. Nitrogen fixation became important not only for the production of ammonium sulphate and nitrate fertilizers but for the manufacture of nitric acid, much in demand before and during the wars for making explosives. As to phosphorus, the main source until around 1900 was ground bones or bone meal, but in the last decades of the nineteenth century large deposits of calcium phosphate were discovered in northern Africa and, later, other major producers were the USA, USSR and the Pacific island of Nauru. The calcium phospate is converted to ‘superphosphate’ by treatment with sulphuric acid, first achieved on a large scale from 1834 by John Bennet Lawes at Rothamsted in Hertfordshire. ‘Triple superphosphate’, or monocalcium phosphate produced by treating the mineral form with phosphoric acid, attained equal importance with the ‘super’ variety in the USA in the 1960s. Potassium fertilizers (potash), mainly potassium chloride, have been applied as they were mined, the Stassfurt region in Saxony being the leading source for some 130 years. Electrolysis An entirely new way of producing chemicals arose towards the end of the last century. Electricity had been used to decompose substances, for example by Sir Humphry Davy in 1807 in obtaining sodium metal for the first time, but it was not until cheap supplies of electricity were available that electrolytic methods of preparing chemicals became commercially viable. In 1890 an American working in Britain, Hamilton Castner, developed a method of producing sodium by electrolysis of molten caustic soda, for use in the making of aluminium. At the moment of success, an electrolytic method of preparing aluminium was achieved by Hall and Héroult (see pp. 107–9), rendering the sodium superfluous. But relief was at hand. The ‘gold rushes’ of the 1890s dramatically increased the demand for sodium, in the form of its cyanide, used in the purification of gold and silver. THE CHEMICAL AND ALLIED INDUSTRIES 225 Castner then worked out a cell for making high-purity caustic soda, by electrolysis of brine over a mercury cathode and carbon anodes. The sodium released formed an amalgam with the mercury which, by rocking, came into contact with water in a central compartment; there, it reacted with the water to form caustic soda. An Austrian chemist, Carl Kellner, was working along similar lines and to avoid unpleasant patent litigation, the two came to an arrangement, with the result that the cell is known as the Castner-Kellner cell. The Castner cell was later modified, particularly by J.C.Downs’s patent of 1924, defining the electrolysis of molten sodium chloride with graphite anode and surrounding iron gauze cathode, and using calcium chloride to lower the melting point of the electrolyte. This was a more efficient process electrically, although until 1959 both cells were in use, to provide cheap sodium. Other heavy chemicals were made by electrolytic methods from around 1900, such as sodium chlorate, much used as a herbicide. FURTHER READING Chandler, D. and Lacey, A.D. The rise of the gas industry in Britain (Gas Council, London, 1949) Clark, J.A. The chronological history of the petroleum and natural gas industries (Clark Book Co, Houston, Texas, 1963) Douglas, R.W. and Frank, S. A history of glassmaking (G.T.Foulis, Henley-on-Thames, 1972) Haber, L.F. The chemical industry during the nineteenth century (Clarendon Press, Oxford, 1958) —— The chemical industry 1900–1930 (Clarendon Press, Oxford, 1971) Hardie, D.W.F. and Pratt, J.D. A history of the modern British chemical industry (Pergamon Press, Oxford, 1966) Kaufman, M. The first century of plastics (Plastics Institute, London, 1963) Longstaff, M. Unlocking the atom: a hundred years of nuclear energy (Frederick Muller, London, 1980) Nef, J.U. The rise of the British coal industry (Routledge, London, 1932) Russell, C.A. Coal: the basis of nineteenth century technology (Open University Press, Bletchley, 1973) —— ‘Industrial chemistry’ in Recent developments in the history of chemistry (Royal Society of Chemistry, London, 1985) Singer, C. et al (eds.) A history of technology, 7 vols., each with chapters on industrial chemistry (Clarendon Press, Oxford, 1954–78) Taylor, F.S. A history of industrial chemistry (Heinemann, London, 1957) Warren, K. Chemical foundations: the alkali industry in Britain to 1920 (Clarendon Press, Oxford, 1980) Williams, T.I. The chemical industry past and present (Penguin Books, Harmondsworth, 1953) —— A history of the British gas industry (Oxford University Press, Oxford, 1981) PART TWO POWER AND ENGINEERING 229 4 WATER, WIND AND ANIMAL POWER J.KENNETH MAJOR The three main forms of natural power have a long history of development, and since classical times the development of water and wind power has been interrelated. The use of all three forms has not ceased, for water and wind power are gradually coming back into use as alternatives to the fossil fuels—oil and coal — and to nuclear fission. The need to develop rural communities in the Third World has brought about a rediscovery of the primitive uses of water, wind and animal power which can remain within the competence of the rural craftsmen. WAT E R P OW E R The ancient world The first confirmed attempts to harness water to provide power occurred in the Fertile Crescent and the countries that border the eastern Mediterranean, in the centuries before the birth of Christ. The harnessing of these natural forms of power grew out of the difficulties of grinding grain by hand or raising water for irrigation laboriously by the bucketful. Slaves were not cheap, and the milling of enough flour by hand became increasingly expensive. At first the grain was ground by being rubbed between two stones known as querns. The grain would rest on a stone with a concave upper face and would be rubbed with a large smooth pebble. The next stage was to shape a bottom quern and to have a top stone which matched it and which could be pushed from side to side over the grain. By making both upper and lower stones circular, and by fixing a handle in the upper stone, a rotary motion was imparted to the hand quern. From that it is a short step to mounting the quern on a frame and having a long handle to rotate the upper millstone. PART TWO: POWER AND ENGINEERING 230 The first attempt to power millstones with water resulted in a form of watermill which we now call the Greek or Norse mill (see Glossary). In this the two millstones—derived from rotary hand-processing—were mounted over a stream with a high rate of fall. The lower millstone was pierced and mounted firmly in the mill, and the upper (runner) millstone was carried on a rotating spindle which passed through the lower millstone. This spindle was driven by a horizontal waterwheel which was turned by the thrust of water on its blades, paddles or spoon-shaped buckets. The stream was arranged, possibly by damming, to give a head of water, and this head produced a jet of water which hit and turned the paddles of the horizontal waterwheel. The horizontal watermill was a machine, albeit primitive, which ground grain faster than it could be ground by hand, and soon improvements began which further increased the speed of grinding. The Romans adopted the Greek mill and made the hand mill more profitable by turning it into a horse-driven mill. Roman Europe became a civilization in which the countryside supported a growing number of larger towns. The use of slaves or servants to grind the grain for the family became too expensive, and there was a real need to increase the production of meal from the millstones. The often-quoted example of the range of ass-driven hourglass mills in Pompeii (see p. 262) shows how a town bakery was able to produce large quantities of meal for sale or for a baker’s shop. The Romans are thought to have been the inventors of the vertical waterwheel. In this system a waterwheel is turned in a vertical plane about a horizontal shaft and the millstones are driven from this by means of gear wheels. About 25 BC Vitruvius wrote De Architecture, and in the tenth book he describes the vertical waterwheel and its gear drive to the millstones. The earliest form of mill in which a single pair of millstones is driven by a waterwheel is therefore known as the Vitruvian mill. Many examples of the Vitruvian mill have come to light in archaeological excavations. The most famous of all the Roman Vitruvian mills is the group at Barbegal near Arles, in the Bouches-du-Rhône department of France. Here an aqueduct and channel delivered water to a chamber at the top of a steep slope. The water descended in two parallel streams, and between the streams there were the mill buildings. There were sixteen overshot waterwheels in two rows of eight, the water from one wheel driving the next one below it. This example from c. AD 300 shows a sophistication in millwrighting design which typifies the Roman approach to many of their problems of engineering and architecture. There are representations of vertical waterwheels in Byzantine art and in the Roman catacombs. By Hadrian’s Wall in 1903, Dr Gerald Simpson excavated a Roman watermill which dates from c. AD 250. Lord Wilson of High Wray prepared drawings of this which were published in Watermills and Military Works on Hadrian’s Wall in 1976. Similar and more important excavations, carried out in Rome in the 1970s by Schiøler and Wikander, show how universal the spread of the Vitruvian mill was in the Roman period. WATER, WIND AND ANIMAL POWER 231 Further archaeological evidence confirms the presence of Roman watermills in Saalburg, near Bad Homburg in Germany, and Silchester, Hampshire. The Romans and their colonials were among the first people to dig mines for metals. In some of these deep mines there was a need to install mechanical water- raising devices and in the mines at Rio Tinto in south-west Spain a substantial water-lifting wheel has been found. While this is not strictly a waterdriven wheel it is analogous. The large rim carries a series of wooden boxes which have side openings at the upper ends. The wheel is turned by men pulling on the spokes and the boxes lift the water so that it empties out at high level into a trough which leads it away from the wheel. This wheel is one form of water-raising device and its derivatives still exist in parts of Europe and the Near East. The best-known examples are those at Hama in Syria, where waterdriven wheels carry containers on the rim which raise the water to the top of the wheel where it empties out into irrigation channels. The biggest of these is 19.8m (65ft 6in) in diameter. Mediaeval and Renaissance Europe As a result of archaeological excavation, the Dark Ages are now producing examples of water-powered devices, and more attention is being paid to these examples. At Tamworth in Staffordshire the excavation of a watermill shows evidence of a well-designed mill of the Saxon period. These excavations revealed that the mill had been powered by two horizontal waterwheels housed in wooden structures. The mediaeval period gives us our first real insight into the growth of water power in Europe. In England, the Domesday survey of 1086 gives a record of the number of mills in England—some 5000. While all the counties in the country were not surveyed, those that were show a surprising number of mills in relation to the manors, villages and estates. It must not be taken for granted that all the mills were water driven: hand mills may be indicated by the low level of their rents. Similarly, it must not be assumed that the mills were separate buildings, just that there was more than one waterwheel. The documents, cartularies, leases and grants of land give a greater insight into the way in which the use of water power was developing. All over Europe the abbeys, manors and towns were building watermills, and while most of these were corn mills, there is evidence of the construction of fulling mills, iron mills and saw mills. For example, the most famous drawings of a saw mill were made by Villard de Honnecourt in 1235. A mill built to his drawings was erected as a monument to him at Honnecourt sur Escaut, France. In this mill the waterwheel rotated as an undershot or stream wheel, and by means of cams the reciprocal motion was given to the saw blades. Although it cannot be assumed that this was the first saw mill, it is the first positive document showing the mechanism to have survived. . this became the most widely used material. Explosives Another important branch of the chemical industry was the manufacture of explosives (see Chapter 21). Until the middle of the nineteenth century, the. grain faster than it could be ground by hand, and soon improvements began which further increased the speed of grinding. The Romans adopted the Greek mill and made the hand mill more profitable by. of the world supply. By the 1960s this figure had shrunk to 1–2 per cent. The reason for the decline was the successful tapping of the richest source of nitrogen of all: the air we breathe. The