produced by Catalytic Bodies. 211 



+ HO=4C02 + 2 (C4 Hg O2). To show the exact similarity 

 of the two processes of oxidation when the assisting body is 

 either organic or inorganic, I may cite the curious manufac- 

 turing process for oxidizing oils in the method of dyeing 

 Turkey-red used in this country, and included in Mercer's 

 patent for that colour. It consists in oxidizing oils by blow- 

 ing hot air through them, the oils being in contact with a 

 solution of a salt of copper or of bran ; the contact of either 

 of these solutions is found very materially to accelerate the 

 oxidation. The catalytic action of oxide of copper in evolving 

 oxygen from hypochlorite of lime was adduced as showing its 

 affinity for more oxygen, and this feeble affinity is well known 

 and used empirically by all calico-printers, who are in the con- 

 stant habit of mixing a salt of copper with their colours for 

 the purpose of ageing them more speedily ; in other words, of 

 causing them to unite with oxygen. This also is the assisting 

 cause in Mercer's process for oxidizing oils ; bran in solution 

 answers the same purpose from its affinity for oxygen. The 

 addition of common salt or muriate of ammonia favours the 

 oxidation in all the cases referred to, the oxidation proceeding 

 much more quickly in their presence. No sub-chloride is 

 ever formed, the action being purely catalytic, and probably 

 depending on the conversion of the salt of copper into a 

 chloride, the chlorine of which may be supposed to exert 

 a slight affinity for the hydrogen of the compound, thus 

 withdrawing it somewhat from the sphere of its own special 

 attractions in the body; the copper now aiding the chlorine, 

 delivers the hydrogen more easily into the power of the oxy- 

 gen of the atmosphere. It is therefore immaterial whether 

 the body exercising the assistant affinity be organic or inor- 

 ganic, if the conditions be favourable to the exercise of this 

 influence. The action of a body in acetous fermentation on 

 the transformation of bi'andy into vinegar must be recognised 

 as a phenomenon of a like kind. We know that brandy may 

 trickle m ithout change over a large surface of wood shavings, 

 through which air circulates at the heat of the human body, 

 but that it is quickly converted into vinegar if brandy in the 

 act of oxidation be mixed with it. Here the added ferment 

 exerts its assisting affinity in precisely the same way as the 

 salt of copper, when it aids the oxidation of oils or colours, 

 or as protonitrate of manganese or peroxide of nitrogen 

 during the oxidation of starch. The conversion of hydrogen 

 and oxygen into Mater by the action of fermenting silk, cot- 

 ton, or woody fibre, as observed by Saussure, is obviously a 

 phaenomenon of the same kind, and can only be exerted 

 slowly and in the immediate vicinity of the assisting oxidi- 



P2 



