410 STUDIES ON THE PHENOMENA OF CONTACT 



The first retort will, in these circumstances, yield gases and the ordinary em- 

 pyreumatic products. The other, on the contrary, will give crystallized pro- 

 ducts. This, however, is but one example in a thousand. In one case the 

 reaction is more ready than in the other, consequently the products should be 

 different. A body susceptible of yielding a gas by the action of heat will 

 yield this gas at a temperature mixch lower — that is, more easily, Avhen it is 

 mixed with another body which cannot combine with any of the elements 

 submitted to experiment. 



Supposing that we submit to the action of heat a hinary body to which we 

 add a third clement ; whether this third body combines with one of the elements 

 of the binary body, or does not so combine, its presence will always facilitate 

 the reaction which takes place, by the development of polarity in which this 

 third body bears a part. 



That the exact knowledge of the modes of action of a third body may be- 

 come of great utility to the chemist the following example, familiar to all, will 

 show. To procure oxygen by means of the chlorate of potassa, we shall 

 economize combustible matter by introducing a body foreign to the reaction, 

 for instance, clippings of platina, sand, peroxide of manganese, &c., &c. 



It is some years since M. Millon remarked, that zinc dissolves much 

 more rapidly, and produces at the same time much more hydrogen, when a 

 metal less electro-positive is added to the sulphuric acid. This is the type of 

 catalytic phenomena in general. A little of the chloride of platinum, mixed 

 with the sulphuric acid, gives rise to a disengagement of hydrogen one 

 hundred and fifty times stronger than that which the same surface of zinc would 

 produce in the pure acid, of the same degree of concentration, and in the same 

 time. This experiment is, as we see, a simple modification of another well 

 known one, Avhich consists in surrounding the zinc with a wire of platina to 

 accelerate the solution ; for the platinum of the chloride is precipitated on the 

 zinc, and forms with it a voltaic element. 



Hydrochloric acid mixed with a little chloride of platinum dissolves lead and 

 copper with a disengagement of hydrogen. The first dissolves it in this way 

 when cold, the second only when heated, but the disengagement is as rapid 

 with the zinc. 



Before concluding this memoir, we should endeavor to compare the relations 

 of the phenomenon of polarity, with what is called chemical affinity. And in 

 the first place, when we speak of polarity, we exjjress a fact verified by ex- 

 periment — a fact which has nothing in common with the so-called "catalytic 

 force, " of tohich it is impossible to verify a single inoperty. Every chemist 

 knows that the phenomenon of polarity manifests itself in every chemical 

 reaction. We have shown in the present paper that it manifests itself equally 

 in catalytic phenomena. We verify polarity by direct experiment, as has been 

 shown. This, then, is not a word exchanged for the word catalysis, but is a fact 

 well established. 



We have already shown how much the phenomenon of polarity influences 

 chemical reaction. Is it the cause of afiiuity, or is affinity itself a force sui 

 generis 1 Borzelius remarked, in regard to the before-cited experiments of 

 Millon, " These experiments show clearly that the greater or less affinity of the 

 acid for the metal, and, reciprocally, is due to the more electro-positive state 

 which results from the contact of the metal deposited ; and that it is this state 

 which induces the affinity, but not inversely the affinity Avhich induces the 

 electric state." In effect, one party thinks electricity or polarity produces 

 chemical action, while another supposes that all electricity is produced by 

 chemical action. Either explanation is simply absurd. Experiment shows 

 that the phenomenon of polarity is an electrical phenomenon if you choose — 

 accompanies chemical action cveryvjhere ; but we cannot thence conclude that 



