mercury process

1) Техника: меркурография

2) Нефть: процесс с ртутным теплоносителем

<chem.proc> ■ Amalgamverfahren n

<el> ■ Quecksilberverfahren n

SUBJECT AREA: Photography, film and optics

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The son of a minor official in a magistrate's court, Daguerre showed an early aptitude for drawing. He was first apprenticed to an architect, but in 1804 he moved to Paris to learn the art of stage design. He was particularly interested in perspective and lighting, and later showed great ingenuity in lighting stage sets. Fascinated by a popular form of entertainment of the period, the panorama, he went on to create a variant of it called the diorama. It is assumed that he used a camera obscura for perspective drawings and, by purchasing it from the optician Chevalier, he made contact with Joseph Nicéphore Niepce. In 1829 Niepce and Daguerre entered into a formal partnership to perfect Niepce's heliographic process, but the partnership was dissolved when Niepce died in 1833, when only limited progress had been made. Daguerre continued experimenting alone, however, using iodine and silver plates; by 1837 he had discovered that images formed in the camera obscura could be developed by mercury vapour and fixed with a hot salt solution. After unsuccessfully attempting to sell his process, Daguerre approached F.J.D. Arago, of the Académie des Sciences, who announced the discovery in 1839. Details of Daguerre's work were not published until August of that year when the process was presented free to the world, except England. With considerable business acumen, Daguerre had quietly patented the process through an agent, Miles Berry, in London a few days earlier. He also granted a monopoly to make and sell his camera to a Monsieur Giroux, a stationer by trade who happened to be a relation of Daguerre's wife. The daguerreotype process caused a sensation when announced. Daguerre was granted a pension by a grateful government and honours were showered upon him all over the world. It was a direct positive process on silvered copper plates and, in fact, proved to be a technological dead end. The future was to lie with negative-positive photography devised by Daguerre's British contemporary, W.H.F. Talbot, although Daguerre's was the first practicable photographic process to be announced. It captured the public's imagination and in an improved form was to dominate professional photographic practice for more than a decade.

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SUBJECT AREA: Chemical technology

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Around 1850, the exciting new metal aluminium began to be produced by the process developed by Sainte-Claire Deville. However, it remained expensive on account of the high cost of one of the raw materials, sodium. It was another thirty years before Castner became the first to work successfully the process for producing sodium, which consisted of heating sodium hydroxide with charcoal at a high temperature. Unable to interest American backers in the process, Castner took it to England and set up a plant at Oldbury, near Birmingham. At the moment he achieved commercial success, however, the demand for cheap sodium plummeted as a result of the development of the electrolytic process for producing aluminium. He therefore sought other uses for cheap sodium, first converting it to sodium peroxide, a bleaching agent much used in the straw-hat industry. Much more importantly, Castner persuaded the gold industry to use sodium instead of potassium cyanide in the refining of gold. With the "gold rush", he established a large market in Australia, the USA, South Africa and elsewhere, but the problem was to meet the demand, so Castner turned to the electrolytic method. At first progress was slow because of the impure nature of the sodium hydroxide, so he used a mercury cathode, with which the released sodium formed an amalgam. It then reacted with water in a separate compartment in the cell to form sodium hydroxide of a purity hitherto unknown in the alkali industry; chlorine was a valuable by-product.

In 1894 Castner began to seek international patents for the cell, but found he had been anticipated in Germany by Kellner, an Austrian chemist. Preferring negotiation to legal confrontation, Castner exchanged patents and processes with Kellner, although the latter's had been less successful. The cell became known as the Castner-Kellner cell, but the process needed cheap electricity and salt, neither of which was available near Oldbury, so he set up the Castner-Kellner Alkali Company works at Runcorn in Cheshire; at the same time, a pilot plant was set up in the USA at Saltville, Virginia, with a larger plant being established at Niagara Falls.

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SUBJECT AREA: Electricity, Photography, film and optics

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At the age of 14 Swan was apprenticed to a Sunderland firm of druggists, later joining John Mawson who had opened a pharmacy in Newcastle. While in Sunderland Swan attended lectures at the Athenaeum, at one of which W.E. Staite exhibited electric-arc and incandescent lighting. The impression made on Swan prompted him to conduct experiments that led to his demonstration of a practical working lamp in 1879. As early as 1848 he was experimenting with carbon as a lamp filament, and by 1869 he had mounted a strip of carbon in a vessel exhausted of air as completely as was then possible; however, because of residual air, the filament quickly failed.

Discouraged by the cost of current from primary batteries and the difficulty of achieving a good vacuum, Swan began to devote much of his attention to photography. With Mawson's support the pharmacy was expanded to include a photographic business. Swan's interest in making permanent photographic records led him to patent the carbon process in 1864 and he discovered how to make a sensitive dry plate in place of the inconvenient wet collodian process hitherto in use. He followed this success with the invention of bromide paper, the subject of a British patent in 1879.

Swan resumed his interest in electric lighting. Sprengel's invention of the mercury pump in 1865 provided Swan with the means of obtaining the high vacuum he needed to produce a satisfactory lamp. Swan adopted a technique which was to become an essential feature in vacuum physics: continuing to heat the filament during the exhaustion process allowed the removal of absorbed gases. The inventions of Gramme, Siemens and Brush provided the source of electrical power at reasonable cost needed to make the incandescent lamp of practical service. Swan exhibited his lamp at a meeting in December 1878 of the Newcastle Chemical Society and again the following year before an audience of 700 at the Newcastle Literary and Philosophical Society. Swan's failure to patent his invention immediately was a tactical error as in November 1879 Edison was granted a British patent for his original lamp, which, however, did not go into production. Parchmentized thread was used in Swan's first commercial lamps, a material soon superseded by the regenerated cellulose filament that he developed. The cellulose filament was made by extruding a solution of nitro-cellulose in acetic acid through a die under pressure into a coagulating fluid, and was used until the ultimate obsolescence of the carbon-filament lamp. Regenerated cellulose became the first synthetic fibre, the further development and exploitation of which he left to others, the patent rights for the process being sold to Courtaulds.

Swan also devised a modification of Planté's secondary battery in which the active material was compressed into a cellular lead plate. This has remained the central principle of all improvements in secondary cells, greatly increasing the storage capacity for a given weight.

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SUBJECT AREA: Photography, film and optics

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Born of French parents, Lippman's work began with a distinguished career in classics, philosophy, mathematics and physics at the Ecole Normale in Luxembourg. After further studies in physics at Heidelberg University, he returned to France and the Sorbonne, where he was in 1886 appointed Director of Physics. He was a leading pioneer in France of research into electricity, optics, heat and other branches of physics.

In 1886 he conceived the idea of recording the existence of standing waves in light when it is reflected back on itself, by photographing the colours so produced. This required the production of a photographic emulsion that was effectively grainless: the individual silver halide crystals had to be smaller than the shortest wavelength of light to be recorded. Lippman succeeded in this and in 1891 demonstrated his process. A glass plate was coated with a grainless emulsion and held in a special plate-holder, glass towards the lens. The back of the holder was filled with mercury, which provided a perfect reflector when in contact with the emulsion. The standing waves produced during the exposure formed laminae in the emulsion, with the number of laminae being determined by the wavelength of the incoming light at each point on the image. When the processed plate was viewed under the correct lighting conditions, a theoretically exact reproduction of the colours of the original subject could be seen. However, the Lippman process remained a beautiful scientific demonstration only, since the ultra-fine-grain emulsion was very slow, requiring exposure times of over 10,000 times that of conventional negative material. Any method of increasing the speed of the emulsion also increased the grain size and destroyed the conditions required for the process to work.

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