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In the next section, “On Some General Observations on these Phenomena, and on the Mode of Decomposition and Transition,” he summarises the foregoing results:—
“It will be a general expression of the facts that have been detailed, relating to the changes and transitions by electricity, in common philosophical language, to say that hydrogen, the alkaline substances, the metals, and certain metallic oxides, are attracted by negatively electrified metallic surfaces, and repelled by positively electrified metallic surfaces; and contrariwise, that oxygen and acid substances are attracted by positively electrified metallic surfaces, and repelled by negatively electrified metallic surfaces; and these attractive and repulsive forces are sufficiently energetic to destroy or suspend the usual operation of elective affinity.
“It is very natural to suppose, that the repellent and attractive energies are communicated from one particle to another particle of the same kind, so as to establish a conducting chain in the fluid; and that the locomotion takes place in consequence; and that this is really the case seems to be shown by many facts. Thus, in all the instances in which I examined alkaline solutions through which acids had been transmitted, I always found acid in them whenever any acid matter remained at the original source....
“In the cases of the separation of the constituents of water, and of solutions of neutral salts forming the whole of the chain, there may possibly be a succession of decompositions, and recompositions throughout the fluid. And this idea is strengthened by the experiments on the attempt to pass barytes through sulphuric acid, and muriatic acid through solution of sulphate of silver, in which as insoluble compounds are formed and carried out of the sphere of the electrical action, the power of transfer is destroyed.”
In the next section, “On the General Principles of the Chemical Changes produced by Electricity,” he points out that it had been already shown by Bennet that many bodies brought into contact and afterwards separated exhibited opposite states of electricity; and that this observation had been confirmed and extended by Volta, who had supposed that it also takes place with regard to metals and fluids. In his paper in the Philosophical Transactions of 1801, the first he sent to the Royal Society, Davy had shown that when alternations of single metallic plates and acid and alkaline solutions were employed in the construction of voltaic combinations, the alkaline solutions always received the electricity from the metal, and the acid always transmitted it to the metal.
In the simplest case of electrical action, the alkali which receives electricity from the metal would necessarily, on being separated from it, appear positive, whilst the acid under similar circumstances would be negative; and these bodies, having respectively with regard to the metals that which may be called a positive and a negative electrical energy, in their repellent and attractive functions seem to be governed by laws the same as the common laws of electrical attraction and repulsion.
The seventh section treats of “The Relations between the Electrical Energies of Bodies and their Chemical Affinities”:—
“As the chemical attraction between two bodies seems to be destroyed by giving one of them an electrical state different from that which it naturally possesses; that is, by bringing it artificially into a state similar to the other, so it may be increased by exalting its natural energy. Thus, whilst zinc, one of the most oxidable of the metals, is incapable of combining with oxygen when negatively electrified in the circuit, even by a feeble power; silver, one of the least oxidable, easily unites to it when positively electrified; and the same thing might be said of other metals. Amongst the substances that combine chemically, all those, the electrical energies of which are well known, exhibit opposite states; thus copper and zinc, gold and quicksilver, sulphur and the metals, the acid and alkaline substances, afford opposite instances; and supposing perfect freedom of motion in their particles or elementary matter, they ought according to the principles laid down, to attract each other in consequence of their electrical powers. In the present state of our knowledge it would be useless to attempt to speculate on the remote cause of the electrical energy, or the reason why different bodies, after being brought into contact should be found differently electrified; its relation to chemical affinity is however, sufficiently evident. May it not be identical with it, and an essential property of matter?”
How Davy sought to elaborate a theory of chemical affinity on these facts will be sufficiently obvious from the following extracts:—
“Supposing two bodies, the particles of which are in different electrical states, and those states sufficiently exalted to give them an attractive force superior to the power of aggregation, a combination would take place which would be more or less intense according as the energies were more or less perfectly balanced; and the change of properties would be correspondently proportional.”
“When two bodies repellent of each other act upon the same body with different degrees of the same electrical attracting energy, the combination would be determined by the degree; and the substance possessing the weakest energy would be repelled; and this principle would afford an expression of the causes of elective affinity and the decompositions produced in consequence.”
“Or where the bodies having different degrees of the same energy, with regard to the third body, had likewise different energies with regard to each other, there might be such a balance of attractive and repellent powers as to produce a triple compound; and by the extension of this reasoning, complicated chemical union may be easily explained.”
As the combined effect of many particles possessing a feeble electrical energy may be conceived equal or even superior to the effect of a few particles possessing a strong electrical energy, the same principle may explain the influence of mass action, as elucidated by Berthollet.