This furnace was designed with a view to investigating at temperatures up to 1500° C. certain cases of heterogeneous equilibrium in which the equilibrium is defined by the pressure of the system. Instances are the dissociation of certain oxides, nitrides, and carbonates, and the reduction of oxides by carbon. The furnace could not be constructed of carbon, as carbon would react with some of the gases of which the pressure had to be measured, and also because it is almost impossible to remove the adsorbed gases from large quantities of carbon. Tubes of Royal Berlin porcelain in a platinum-wound resistance furnace may be used for temperatures up to 1200°, but at about this temperature they become soft, while the glaze runs and combines with any boat or other substance in the furnace. Tubes of silica are not suitable, because they are porous at high temperatures, and because they disintegrate owing to crystallisation taking place. It was decided to make the furnace of a platinum tube and to heat it by passing a large current through it. As some of the substances which it would be necessary to place in the furnace react with platinum,
e. g
. copper formed by the dissociation of cuprous oxide, it was necessary to make the furnace sufficiently large to take a boat or crucible of magnesia large enough to contain the reacting substance and thick enough to protect the tube. On the other hand, the tube ought to be as small as possible, in order that in determining the dissociation pressures all the charge should not be decomposed before the equilibrium is attained.
Reduction of Oxides of Nitrogen in Diesel Exhaust with Addition of Methylamine.
