2 50 THE POPULAR SCIENCE MONTHLY, 



trically neutral. This makes almost no difference in the value of the 

 electro-motive force. For instance, if chlorine is separated at the anode 

 it Avill remain at first absorbed by the liquid ; if the solution becomes 

 saturated, or if we make a vacuum over the liquid, the gas will rise in 

 bubbles. The electro-motive force remains unaltered. The same may 

 be observed with all the other gases. You see in this case that the 

 change of electrically negative chlorine into neutral chlorine is the 

 process which requires so great an amount of work, even if the pon- 

 derable matter of the atoms remains where it was. 



The more the surface of the positive electrode is covered with neg- 

 ative atoms of the anion and the negative with the positive ones of the 

 cation, the more the attracting force of the electrodes exerted upon 

 the ions of the liquid is diminished by this second stratum of opposite 

 electricity covering them. On the contrary, the force with which the 

 positive electricity of an atom of hydrogen is attracted toward the 

 negatively charged metal increases in proportion as more negative 

 electricity collects before it on the metal and the more negative elec- 

 tricity collects behind it in the fluid. 



Such is the mechanism by which electric force is concentrated and 

 increased in its intensity to such a degree that it becomes able to over- 

 power the mightiest chemical affinities we know of. If this can be 

 done by a polarized surface, acting like a condenser, charged by a very 

 moderate electro-motive force, can the attractions between the enor- 

 mous electric charges of anions and cations play an unimportant and 

 indifferent part in chemical affinity ? 



You see, therefore, if we use the language of the dualistic theory 

 and treat positive and negative electricities as two substances, the phe- 

 nomena are the same as if equivalents of positive and negative electric- 

 ity were attracted by different atoms, and perhaps also by the differ- 

 ent values of affinity belonging to the same atom, with different force. 

 Potassium, sodium, zinc, must have strong attraction to a positive 

 charge ; oxygen, chlorine, bromine, to a negative charge. 



Faraday very often recurs to this to express his conviction that the 

 forces termed chemical affinity and electricity are one and the same. 

 I have endeavored to give you a survey of the facts in their mutual 

 connection, avoiding, as far as possible, introducing other hypotheses, 

 except the atomic theory of modern chemistry. I think the facts leave 

 no doubt that the very mightiest among the chemical forces are of 

 electric origin. The atoms cling to their electric charges and the op- 

 posite electric charges cling to the atoms. But I don't suppose that 

 other molecular forces are excluded, working directly from atom to 

 atom. Several of our leading chemists have begun lately to distinguish 

 two classes of compounds, molecular aggregates and typical compounds. 

 The latter are united by atomic affinities, the former not. Electrolytes 

 belong to the latter class. 



If we conclude from the facts that every unit of affinity of every 



