Nernst furnace

The historical aspects ofTG have been discussed by Duval (3-5), Wend-Iandt (7), Keattch (23), and others (107-109). Perhaps thejirst thermobalance was that described by Nernst and Riesenfeld (I20X whp used a Nernst quartz torsion microbalance. equipped wit an electric furnace, to study the mass-loss on heating of Iceland spar. opal, zirconia, and other minerals. The Japanese Honda was apparently the first to use the term ihermobalance for an instrument he described in 1915 (9). The French school of thermo-gravimetry began with Urbain in 1912 when he modified two-pan analytical balance into a cril e thermobalance (24). This was followed by the work of Guichard (1923) (10), Vallet (1936), Chevenard (1936), Duval (1950), and many others.The first commercial thermobalance in the United States, which prompted funner work in TG. was that described by Mauer (31) in 1954,... 

The heating element of these furnaces, which were first constructed by Nernst and Tammann, is a carbon tube. Because of their low resistance, they are also called short circuit furnaces. The larger models have foimd wide industrial use. Thus, these furnaces are commercially available. It does not pay to attempt construction of such a imit in the laboratory. The most e q)ensive part is the transformer, needed because of the low resistance of the carbon tube, and this must be purchased in any case. Depending on the size, these units require some 100-1000 amp. at approximately 10 volts. Careful construction of the unit permits easy replace-mait of the carbon tube (whose durability at high temperature is limited). Temperatures of over 2000°C can easily be reached. A reducing atmosphere must always be maintained inside the tube. Should this be undesirable, then protective insert tubes must be provided. For this purpose, alumina can be used iq) to 2000°C. At higher temperatures, only sintered BeO or ThOg is effective MgO is subject to reduction. 

Nernst and his pupils carried out important work on gaseous equilibria and specific heats of gases at high temperatures. Vapour densities were measured in a small iridium Victor Meyer apparatus heated in an iridium tube furnace to over 2000" C., quantities of about o ooi mg. being weighed in an ingenious microbalance devised by Nernst. Dissociation was measured by heating a... 

In 1906 he published his heat theorem, which soon became widely known as the third law of thermodynamics and which earned him a Nobel Prize for physics in 1920. A discrepancy arising from this thermodynamic research led indirectly to Haber s eventual success. In his review of existing equilibria measurements Nernst discovered that the values for ammonia published in 1905 by Haber and van Oordt were the only ones seriously at variance with his heat theorem. He entrusted his assistant Fritz Jost to replicate the experiment, using a small iridium apparatus heated in an iridium furnace to more than 2,000 °C and an ingenious microbalance of his own design. In order to increase the equilibrium ammonia concentration he... 

---