Tube furnace

In solid state chemistry, a tube furnace is a heating device for conducting 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 imbedded 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.

An example of a material prepared in a tube furnace is the superconductor YBa₂Cu₃O₇. Finely powdered CuO, BaO, and Y₂O₃, in the appropriate molar ratio is placed in a platinum or alumina "boat" which is inserted into the furnace. Most commonly reactions are conducted in tubes made of Pyrex or amorphous silica.

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 pyrolysis/thermolysis utilizes a quartz glass tube, usually packed with quartz or ceramic beads, which is heated to extreme temperatures.