396 STUDIES ON THE PHENOMENA OF CONTACT. 



Fig. 1. Wc call this polarization ; the molecules seem 



A J? to assume 2^oles. The combination completed, the 



-i- r^ — _|_ (^ — opposite electricities are given off, as the second 



^'^ figure shows, and, by intercepting them with a 



galvanometer, we identify their nature ; we prove, by direct ex- Fig. 2. 



periment, that oiccixo-negative bodies, like the acids, give off the -^ ^ 



positive electricity, while the bases or aXQctvo-joositive bodies, ■(r~Kw''- 

 under these circumstances, give off the negative electricity. /' \ 



This principle governs all chemical reaction, however com- ■ ; 



plicated it may appear. And whatever may be the modifica- \^ 



tions recently introduced into our ideas respecting light, heat, '"A '' 



electricity, affinity, &c., by the imposing doctrine of the correlation ofjyhysical 

 forces, we shall continue, in speaking chemically, to consider chemical reaction, 

 the combination and decomposition of bodies, in this manner. For, without 

 affirming that this is, at the present epoch of science, the most rational manner 

 of consideration, we are able, in this way, not only to present a theory easily 

 apprehended and borne out by all experiments, but haVe it further in our power 

 to explain, to a certain point, by a profound study of the phenomenon of polarity, 

 almost all the facts thus far observed in the vast domain of chemistry. 



I shall not inquire, in this place, whether chemical affinity be a force apart 

 S7d generis, or a necessary effect of the polarization of molecules. Something 

 will be said on this subject towards the close of this memoir. I affirm only 

 that the phenomenon which we call polariUj accompanies and controls all com- 

 binations and decompositions of bodies. 



This being premised, it still remains to demonstrate that the polarity of a 

 body is not fixed ; that it varies according to the bodies with which it is brought 

 into contact. To cite an example familiar to all my readers, chlorine, one of 

 the most electro-negative of metaloids, becomes electro-positive in its relations 

 with organic bodies, and even in relation to oxygen, under certain circum- 

 stances. What is thus said of chlorine is also applicable to iodine, bromine, 

 fluorine, &c.; in a word, to all analogous bodies. Sulphur, agreeabiy to the ex- 

 periments of M. Befthelot, is sometimes positive, sometimes negative, according 

 to circumstances. Chlorine, in the chlorides, is electro-negative ; in the 

 chlorates, it is electro-positive ; and in them the nitrate of silver does not evince its 

 presence, &c., &c. Thus we find that the polarity of a body changes according 

 to the bodies with which Ave place it in contact. The change consists in the 

 body submitted to experiment becoming electro-negative or electro-positive, 

 from having jncvioushj been electro-positive or electro-negative. 



But we can modify in a different manner the polarity of a body ; that is, we 

 can render it viorc or less electro-p>ositive, more or less electro-negative, and that 

 without the body entering into combination with one of those which induce 

 this change. Thus, by the contact of a stick of phosphorus, the polarity of the 

 oxygen contained in a volume of humid air passes into an allotropic state — into 

 ozone. Its polarity is thereby modified to an extraordinary degree ; it is 

 much more electro-negative than in other circumstS-nces. If we decomj)Ose 

 water by means of the pile, and collect the oxygen produced hi the pores of a 

 charcoal pole, this oxygen is modified in the same manner. — {Osa?m.) If 

 we disengage it from the bi-oxide of barj^ta by sulphuric acid, at the ordi- 

 nary temperature, the effect is the same. — (Houzeau.) If, observing certain 

 precautions, we disengage it by heat from the peroxide of lead, from the oxide 

 of mercury, &c., we find that a certain quantity is in the state of ozone. — 

 ( ScJionbciyi.J When ordinary oxygen enters into combination with certain 

 organic bodies, it passes into the state of ozone. — ( Schonhein, Kuldmann, and 

 Pliijjson.) Not needlessly to multiply these examples, we shall only say that 

 the same is the case with chlorine, with bromine, ( Andrcios,) and with hydro- 

 gen, ( Osann,) as shown by experiments results of which can bear but one inter- 



