A text-book of inorganic chemistry / by Dr. A.F. Holleman ... Issued in English in coöperation with Hermon Charles Cooper.

  • Arnold F. Holleman
Date:
1912
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Licence: In copyright

Credit: A text-book of inorganic chemistry / by Dr. A.F. Holleman ... Issued in English in coöperation with Hermon Charles Cooper. Source: Wellcome Collection.

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    4. The oxygen of the air can also serve as the oxidi/.ing agent: 21in + () = ll2()+n2. For this purpose a mixture of 00% of air and 40% of liydrogcii chlorkle at about 430° is ])assed over porous Ijric'ks vhich are soaked with copper sulphate solution. About 70%, of the hydro- gen chloride is converted into chloidne. This method, which is known as the Deacon process, is used commercially. The copper sulphate serves as a catalyzer. The progress of chemical changes is often modified by the mere presence of a substance which has the same chemical com- position after the reaction as at the beginning. Such a substance is termed a eatalyzei' and the action which it exerts is called catalysis, or catalytic action. The (juantit} of the catalyzer necessary to exert a pei'ceptible influence is often very small. This is the case, for example, in the combination of hydrogen and oxygen in the presence of platinum as a catalyzer (§ 13, p. IG). A minute trace of platinum sponge brought into contact with detonating-gas accelerates the combination to such a rate that the reaction takes place very quickly and can even become explosive. In the Deacox process a small quantity of copper sulphate suffices to bring into reaction unlimited quantities of hydrogen chloride and oxygen. At the temperature of ^430° there is practically no reaction between oxygen and hydrogen cliloridc without the catalyzer. That there must, nevertheless, be a reaction, although a very slow one, can be demonstrated by the same reasoning as in § 13. The catalyzer thei-efore does not cause a reaction, but only accelerates it. Ostwald compares its action to that of oil on the axles of a machine which move with very great filction. When oiled, the ma- chine will go much faster, notwithstamling that the force of the spring (here the energy of the chemical reaction) has not changed. A further point in the analogy is that the oil is not consumed. In most cases of catalysis it can be proved that the catalyzer takes part in the reaction but at the end of it reappears in its original condition. In the platinum catalysis of detonating-gaij,
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