﻿398 Sir W. Ramsay and Dr. Spencer on Chemical and 



and the doctrine of energetics, strictly applied, as for instance 

 by Ostwald, ignores the " mechanical " nature of energy, and 

 refuses to picture it. Hence, at present at least, almost all 

 physicists and chemists are agreed rather to assign a me- 

 chanical or depictable nature to the electron, and to attempt 

 an explanation of natural phenomena by its means. It may 

 be remarked parenthentically that such considerations closely 

 touch metaphysical speculations ; they differ, however, inas- 

 much as they afford a mental picture and a partial explana- 

 tion of what is actually observed. It is obvious to all, then, 

 that by interaction of atomic sodium and molecular chlorine, 

 common salt is produced. And it is now generally acknow- 

 ledged that when dissolved in water, the salt is " ionized/'' 

 that is the sodium atom has acquired a positive charge, or in 

 terms of electrons, has lost an electron, while the chlorine 

 atom, with its negative charge, is now a chlorion, viz., an 

 atom of chlorine which has gained an electron. But between 

 the physical properties of salt and of its solution there is 

 merely a quantitative difference. The refractive index of salt 

 is lessened by admixture with water ; but a solution of salt 

 has little if any difference in refractive index from the mean 

 of the indices of the mixture of salt and water, taken in the 

 proportion in which they are present in solution. Compouuds 

 which show absorption spectra show the same, or nearly the 

 same spectra in solution : the specific heats of solutions do 

 not greatly differ from that of the mean of the constituents, 

 and so with other physical properties. But most of the pro- 

 perties of compounds differ radically from those of the elements 

 which yield them. It appears probable, therefore, that a 

 molecule of NaCl has been formed from 2Na and Cl 2 by 

 displacement of an electron thus : — 2NaQ + Cl 2 = 2]SraClQ; 

 the electron is now more intimately attached to the chlorine 

 atom ; and if opportunity be given, by the presence of mobile 

 molecules of water, these ions will part from each other into 

 2NaAq + 2ClQAq. It is not necessary here to discuss the 

 protective nature of the water and the possible combination 

 between the ions given above and molecules of the solvent. 

 It will somewhat aid these conceptions if the action of a 

 simple galvanic cell be considered. Suppose a plate of zinc 

 and a plate of copper dipping in dilute hydrochloric acid. 

 When connected by a wire the zinc " dissolves as chloride, " 

 and a current passes through the wire. It has been suggested 

 by Nernst, with useful results, that the zinc possesses a higher 

 " solution pressure " than the copper. That the phenomenon 

 can be " explained " on this hypothesis is obvious. But it 

 conduces to clearness if we regard the sequence of events in 



