As the Badische process effects this prevention by cooling the contact apparatus by means of the gaseous mixture to be later submitted to the catalytic action, the mixture is at the time heated up to the requisite temperature, and a considerable saving of fuel is the consequence.
A further step in this direction has been effected by the introduction of reversibility into a non-reversible case by means of a catalytic agent.
It corresponds to one of the melting-points in the series without catalytic agents, viz.
In that mixture which contains 88% of paraldehyde and 12% of acetaldehyde, which the catalytic agent leaves unaffected.
Oxygen may be prepared by heating mercuric oxide; by strongly heating manganese dioxide and many other peroxides; by heating the oxides of precious metals; and by heating many oxy-acids and oxy-salts to high temperatures, for example, nitric acid, sulphuric acid, nitre, lead nitrate, zinc sulphate, potassium chlorate, &c. Potassium chlorate is generally used and the reaction is accelerated and carried out at a lower temperature by previously mixing the salt with about one-third of its weight of manganese dioxide, which acts as a catalytic agent.