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.
It is mixed with fresh air containing sufficient oxygen for the combustion of the hydrogen, and the mixture is passed through red-hot iron oxide (burnt pyrites) which by its catalytic action causes the reaction H2S+O= H 2 O+S to take place.
Its chemical properties are in general intermediate between those of chlorine and iodine; thus it requires the presence of a catalytic agent, or a fairly high temperature, to bring about its union with hydrogen.
This reaction, now known by the name of the catalytic or contact process, was made the subject of a patent by Peregrine Phillips, in 1831, and was tried later in many ways, but had been always considered as useless for practical purposes until 1875, when it was simultaneously and independently taken up by Clemens Winkler in Freiberg, and by W.
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.
Wharfinger states that in chlorosis the specific action of iron is only obtained by administering those inorganic preparations which give a reaction with the ordinary reagents; the iron ions in a state of dissociation act as a catalytic agent, destroying the hypothetical toxin which is the cause of chlorosis.
Potassium permanganate in acid solution oxidizes it to carbon dioxide and water; the manganese sulphate formed has a catalytic accelerating effect on the decomposition.
This fact explains the so-called "catalytic" action of acids and bases in decomposing such compounds as the esters.
Hydriodic acid, HI, is formed by the direct union of its components in the presence of a catalytic agent; for this purpose platinum black is used, and the hydrogen and iodine vapour are passed over the heated substance.
Chromic chloride, CrC1 31 is obtained in the anhydrous form by igniting a mixture of the sesquioxide and carbon in a current of dry chlorine; it forms violet laminae almost insoluble in water, but dissolves rapidly in presence of a trace of chromous chloride; this action has been regarded as a catalytic action, it being assumed that the insoluble chromic chloride is first reduced by the chromous chloride to the chromous condition and the original chromous chloride converted into soluble chromic chloride, the newly formed chromous chloride then reacting with the insoluble chromic chloride.
Blagden (Ber.,1900,33,p.2544), who consider that three simultaneous reactions occur, namely, the formation of labile double salts which decompose in such a fashion that the radical attached to the copper atom wanders to the aromatic nucleus; a catalytic action, in which nitrogen is eliminated and the acid radical attaches itself to the aromatic nucleus; and finally, the formation of azo compounds.
It has also been shown that when different salts of the amine are used, their catalytic influence varies in amount and is almost proportional to their degree of ionization in aqueous solution.
When a catalytic agent, such as sulphurous acid, is added, which produces a mutual change, the whole behaviour is different; only one meltingpoint, viz.
The only substance which possesses sufficiently strong catalytic properties for the reaction is cupric chloride.