An Encyclopedia of the History of Technology part 17. This one of a kind encyclopedia presents the entire field of technology from rudimentary agricultural tools to communication satellites in this first of its kind reference source. Following an introduction that discusses basic tools, devices, and mechanisms, the chapters are grouped into five parts that provide detailed information on materials, power and engineering, transportation, communication and calculation, and technology and society, revealing how different technologies have together evolved to produce enormous changes in the course of history | PART ONE MATERIALS Figure This cell was used by in 1940 to obtain ductile titanium by reacting titanium tetra-chloride with molten magnesium. This approach which was developed during the war years by the US Bureau of Mines was soon generally adopted as the most feasible method of producing titanium on an industrial scale. Much of the titanium now being made is reduced to metallic form by sodium rather than by magnesium. process in 1939. High purity calcium however which was required with a low nitrogen content was an expensive commodity. Kroll found that titanium tetrachloride could be very effectively reduced by pure magnesium which was cheap and readily available. Details of Kroll s magnesium reduction process were first published in 1940 in the Transactions of the Electrochemical Society of America. By this time Kroll had left Europe to join the United States Bureau of Mines. A simplified version of the reaction vessel in which magnesium reduced titanium was first obtained is shown in Figure . Liquid titanium tetrachloride was dropped on to a bath of molten magnesium held between 142 NON-FERROUS METALS 850 and 950 C in the molybdenum container at the bottom of the cell. Once the reaction started no further heating was required and the temperature was controlled simply by adjusting the rate at which titanium chloride was fed into the reaction vessel. The product of the reaction was titanium sponge which built up in the reaction vessel. Apart from the small quantities of iodide titanium produced by the Van Arkell process Kroll s magnesium reduced titanium was the first which had shown a high degree of room temperature ductility. Titanium is the fourth most abundant metal in the earth s crust after aluminium iron and magnesium. The most valuable deposits are those based on the minerals rutile and ilmenite first found in the Ilmen Mountains of the USSR. The US Bureau of Mines research programme was initially concerned with the exploitation of the .
