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A tube furnace is an electric heating device used to conduct syntheses and purifications of inorganic compounds and occasionally in organic synthesis. The usual design consists of a cylindrical cavity surrounded by heating coils, which are embedded in a thermally insulating matrix. The length of the cylindrical cavity is typically 40 - 60 cm, and the diameters are ca. 8 cm. Temperature is controlled via a feedback from a thermocouple. More elaborate tube furnaces have two (or more) heating zones useful for transport experiments. The temperature controllers often allow the operator to program the heating and cooling rates.^[1]

The tube furnace was invented in the first decade of the 20th century, and was originally used to manufacture ceramic filaments for Nernst lamps and glowers.^[2]

An example of a material prepared using a tube furnace is the superconductor YBa₂Cu₃O₇. A mixture of finely powdered CuO, BaO, and Y₂O₃, in the appropriate molar ratio, contained in a platinum or alumina "boat," heated in a tube furnace at several hundred degrees under flowing oxygen. Most commonly, the tubes are made of Pyrex or fused quartz.^{[citation needed]}

Tube furnaces can also be used for thermolysis reactions, involving either organic or inorganic reactants. One such example is the preparation of ketenes which may employ a tube furnace in the 'ketene lamp'. Flash vacuum pyrolyses often utilize a fused quartz tube, usually packed with quartz or ceramic beads, which is heated at high temperatures.

Finally, tube furnaces are used for chemical vapor transport, a technique for purifying inorganic materials.

[edit] References

1. ^ J. D. Corbett "Synthesis of Solid-State Materials" in Solid State Chemistry: Techniques, A. K. Cheethan and P. Day, Eds. Clarendon, Oxford, 1987. ISBN 0-19-855165-7.
2. ^ Harker, J. A. (December 1905). "On a New Type of Electric Furnace, with a Redetermination of the Melting-Point of Platinum". Proceedings of the Royal Society A 76 (507): 235-249. http://books.google.com/books?id=O_UAAAAAYAAJ&printsec=titlepage&client=firefox-a&source=gbs_navlinks_s.