30 REPORT— 1839. 



in the polar molecule of hydrochloric acid, for instance, are displaced, 

 when the acid acts as an exciting fluid, and the positive electricity is 

 located in the chlorine atom, and the negative electricity in the hydro- 

 gen atom. The electricities are, at the same time, made the deposit- 

 ories of the chemical affinities of the chlorine and hydrogen respec- 

 tively. Mr. Graham proposed to modify this hypothesis so far as to 

 abandon the idea of electricities being actually possessed by these 

 bodies, and to refer the phenomena at once to the proper chemical affi- 

 nities of the bodies. He assigned similarly polar molecules to the 

 exciting fluid and metals ; and taking hydrochloric acid as a type of 

 exciting fluids, he gave to each molecule a pole, having an affinity re- 

 sembling that of chlorine, or chlorous affinity, instead of negative elec- 

 tricity, and another pole, having an affinity resembling that of zinc or 

 hydrogen, or zincous affinity, instead of positive electricity. When zinc 

 and acid are in contact, the polar state of a single chain of molecules 

 might be represented as in the figure. 



SS2SS®@©®© 



The particle of acid B, next the zinc, has its chlorine atom in con- 

 tact with the metal and its hydrogen atom distant from it, marked re- 

 spectively cl and z in the figure. Part of the affinity of cl being en • 

 gaged by the zinc, the hydrogen is so far received from that affinity, 

 and thus attracts the cl of C. Thus, by a sort of induction, the z of B 

 causes the cl of C to be chlorous, or the molecule of acid C to become 

 polar, and that again the molecule D. In the zinc, (the molecule being 

 supposed to contain two chemical atoms,) while the external atom of A 

 becomes zincous, from its contact with the acid, the other atom be- 

 comes chlorous ; so that these atoms of this molecule may be marked 

 cl and z, and so also the molecules E and I of the zinc, which become 

 polar by induction. 



In another diagram Professor Graham showed how this chemico-polar 

 condition is propagated round a voltaic circle. The molecules of the 

 zinc and acid being polar by contact, which is sufficient to develop 

 their affinities, an induction one way through the zinc, and in the op- 

 posite direction through the acid, conspire to produce the same polar 

 condition in the molecules. The result is, that the molecule 2; of A is 

 zincous both primarily and by induction, and its affinity for the atom 

 cl of B greatly increased ; and, consequently, combination can take 

 place between these atoms when the circuit is completed, but not 

 otherwise. 



If the connecting wire be broken, and a decomposable liquid, such 

 as hydriodic acid, be interposed between the extremities, a chain of polar 

 molecules comes also to be established in that liquid, the iodine (which 

 is the analogue of chlorine) being the seat of the chlorous affinity, and 

 the hydrogen the seat of the zincous affinity. The extremity of the 

 wire connected with the copper plate is zincous, or has zincous affinity, 



