Metal Powder Association

1) Metallurgy: M.P.A.

2) Polymers: MPA

SUBJECT AREA: Metallurgy

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The most valuable part of Bessemer's education took place in the workshop of his inventor father. At the age of only 17 he went to London to seek his fortune and set himself up in the trade of casting art works in white metal. He went on to the embossing of metals and other materials and this led to his first major invention, whereby a date was incorporated in the die for embossing seals, thus preventing the wholesale forgeries that had previously been committed. For this, a grateful Government promised Bessemer a paid position, a promise that was never kept; recognition came only in 1879 with a belated knighthood. Bessemer turned to other inventions, mainly in metalworking, including a process for making bronze powder and gold paint. After he had overcome technical problems, the process became highly profitable, earning him a considerable income during the forty years it was in use.

The Crimean War presented inventors such as Bessemer with a challenge when weaknesses in the iron used to make the cannon became apparent. In 1856, at his Baxter House premises in St Paneras, London, he tried fusing cast iron with steel. Noticing the effect of an air current on the molten mixture, he constructed a reaction vessel or converter in which air was blown through molten cast iron. There was a vigorous reaction which nearly burned the house down, and Bessemer found the iron to be almost completely decarburized, without the slag threads always present in wrought iron. Bessemer had in fact invented not only a new process but a new material, mild steel. His paper "On the manufacture of malleable iron and steel without fuel" at the British Association meeting in Cheltenham later that year created a stir. Bessemer was courted by ironmasters to license the process. However, success was short-lived, for they found that phosphorus in the original iron ore passed into the metal and rendered it useless. By chance, Bessemer had used in his trials pig-iron, derived from haematite, a phosphorus-free ore. Bessemer tried hard to overcome the problem, but lacking chemical knowledge he resigned himself to limiting his process to this kind of pig-iron. This limitation was removed in 1879 by Sidney Gilchrist Thomas, who substituted a chemically basic lining in the converter in place of the acid lining used by Bessemer. This reacted with the phosphorus to form a substance that could be tapped off with the slag, leaving the steel free from this harmful element. Even so, the new material had begun to be applied in engineering, especially for railways. The open-hearth process developed by Siemens and the Martin brothers complemented rather than competed with Bessemer steel. The widespread use of the two processes had a revolutionary effect on mechanical and structural engineering and earned Bessemer around £1 million in royalties before the patents expired.

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SUBJECT AREA: Metallurgy

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Of New England ancestry, his family returned there soon after his birth and later moved to Cleveland, Ohio. In 1884, Dow entered the Case School of Applied Science, graduating in science four years later. His thesis dealt partly with the brines of Ohio, and he was persuaded to present a paper on brine to the meeting of the American Association for he Advancement of Science being held in Cleveland the same year. That entailed visits to collect samples of brines from various localities, and led to the observation that their composition varied, one having a higher lithium content while another was richer in bromine. This study of brines proved to be the basis for his career in industrial chemistry. In 1888 Dow was appointed Professor of Chemistry at the Homeopathic Hospital College in Cleveland, but he continued to work on brine, obtaining a patent in the same year for extracting bromine by blowing air through slightly electrolysed brine. He set up a small company to exploit the process, but it failed; the process was taken up and successfully worked by the Midland Chemical Company in Midland, Michigan. The electrolysis required a direct-current generator which, when it was installed in 1892, was probably the first of its kind in America. Dow next set up a company to produce chlorine by the electrolysis of brine. It moved to Midland in 1896, and the Dow Central Company purchased the Midland Chemical Company in 1900. Its main concern was the manufacture of bleaching powder, but the company continued to grow, based on Dow's steady development of chemical compounds that could be derived from brines. His search for further applications of chlorine led to the making of insecticides and an interest in horticulture. Meanwhile, his experience at the Homeopathic Hospital doubtless fired an interest in pharmaceuticals. One of the substances found in brine was magnesium chloride, and by 1918 magnesium metal was being produced on a small scale by electrolysis. An intensive study of its alloys followed, leading to the large-scale production of these important light-metal alloys, under the name of Dowmetals. Two other "firsts" achieved by the company were the synthetic indigo process and the production of the element iodine in the USA. The Dow company became one of the leading chemical manufacturers in the USA, and at the same time Dow played an active part in public life, serving on many public and education boards.

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