406 STUDIES ON THE PHENOMENA OF CONTACT. 



5. Sulphurous and liyponitric acids, (SO^ + AZO*,) when dry, do not 

 react, but if water be added, we obtain (AZO^SO^ + HOSO^) wliich constitutes 

 the crystals of the leaden chamber. 



I would also call to mind that the action of aqua regia on the metals, Avhich 

 I have just cited, has been, for some time past, perfectly explained by 

 chemists, (especially by Professor Koene, of the University of Brussels,) and 

 all are nearly agreed as to the phenomena which present themselves when the 

 two acids (OLH and AZO^) are poured on a metal. Now, have we not, in this 

 case, exactly the same phenomena which are observed when we place spongy 

 platiua in a mixture of oxygen and hydrogen gases 1 



The following experiment, easy to repeat, is a type of many chemical 

 operations, and has not escaped being somej;imes attributed to the " catalytic 

 force:" when dry chalk is placed in a gun barrel, open at the cuds, and 

 heated, the chalk will yield its carbonic acid at a certain temperature, A. 

 But if, while being heated, a current of vapor of water be passed over the 

 chalk, it will yield its carbonic acid at another temperature, B, considerably 

 lower than the temperature A. The explanation of this fact is quite simple. 

 The vapor of water acts here by what is called in chemistry the injluence of the 

 mass. The water is a Aveak base; the chalk a very strong one; yet the 

 volatility of the carbonic acid by heat, joined to the influence which the 

 mass of water exercises, causes the carbonate to yield its acid in presence 

 of the water at a temperature much lower than that which is requisite to pro- 

 duce this phenomenon when the water is not present. It does not follow thence 

 that the water wliich has induced this phenomenon combines with the lime 

 produced. The vapor acts solely as the platina does in Davy's experiment 

 of slow combustion. 



If, in one of the preceding experiments, in which oxygen gas, hydrogen gas, 

 and platina have been brought into contact, we substitute vapor of alcohol for 

 the hydrogen, we shall observe a phenomenon identical with that which is 

 presented by the two simple gases. The alcohol will be burned like the 

 hydrogen. In place of water we shall have aldehyde as the product, and the 

 explanation of the phenomenon wll remain the same. There is, in effect, a de- 

 velopment of polarity between the three bodies, and a pile might be quite as 

 well constructed by replacing the hydrogen in the pile of Grove with vapor of 

 alcohol, xilcohol, which is always more or less electro-positive in relation to 

 oxygen, becomes, by the presence of the platina, much more electro-positive ; 

 tlie oxygen tends, thereby, to combine with it, and this tendency naturally 

 determines the formation of aldehyde and acetic acid. The same phenomenon 

 presents itself when other vapors are substituted for that of alcohol, such as 

 those of different essences or essential oils, of ether, oil of naphtha, &c. 



In these circumstances, when in place of platina other metals or non-metallic 

 bodies are employed, it is often necessary, in order that the action should man- 

 ifest itself with all its intensity, to add the agency of heat, that the phenomenon 

 of polarity may manifest itself and the combinations take place. But, in all 

 cases, it will never be necessary to raise the temperature to so high a degree, in 

 order to produce these phenomena, as it would be without the presence of the 

 third body. 



The presence of a third body may effect or facilitate decompositions, as 

 well as combinations, in accordance with the same law. Thus, in a mixture of 

 nitrous acid gas and hydrogen, the former gas is decomposed under the influence 

 of the platina sponge. All the oxides of nitrogen in this case yield ammonia. 

 Iron, copper, gold, &c., have the property of decomposing ammonia, if a little 

 heat be applied : and, according to Davy, nitrous acid may be formed under 

 these circumstances, (the presence of a metal,) at the expense of cyanogen 

 and oxygen, whereas, in the same case, cyanogen and hydrogen give cyanuret 

 of ammonia. 



