24 Mr. S. U. Pickering on the Theory of 



dissociated atoms, though no longer held together by chemical 

 attraction, may be still held together by the electrical attraction 

 of their charges. This seems to be but an attempt to over- 

 come a difficulty by changing a name, and so far from really 

 diminishing the difficulty, it would appear only to increase it : 

 for heat has been evolved, and, therefore, the state of com- 

 bination is more intimate than it was before dissolution, so 

 that the matter must be held more firmly together by these 

 electrical charges than it was by its chemical affinity: how 

 does this help the statement that they are less firmly united 

 now — so much less firmly according to the theory, that they 

 act as independent units ? The difficulties as to the origin of 

 the charges and the antagonism of chemical and electrical 

 attraction are, moreover, not removed by this method of ex- 

 pressing the theory. 



Another view, again, was suggested at the recent meeting 

 of the British Association : that, instead of regarding the 

 ions as atoms with electric charges, they might be regarded 

 as allotropic modifications of the atoms themselves. This 

 appears to me to be but hypothecating a new form of matter 

 to satisfy a theory which is inconsistent with known matter, 

 and, inasmuch as atoms of the same substance cannot differ 

 from each other except by possessing different quantities of 

 energy, it practically amounts to the conjuring away a stock 

 of energy that the theory may not be said to be contradicted 

 by the principle of the conservation of energy. But surely 

 such a process is in reality as much a violation of this principle 

 as writing 2 = 4 would be. The energy equation will not 

 equate, so the excess of energy on the one side is boldly struck 

 off by imagining a new form of energyless atom, just as on 

 the electric-charge theory the same is done by saying that 

 the superabundant energy has been expended in combining 

 with charges which have come from nowhere. 



Whereas the potential energy of the ions of a substance 

 such as hydrochloric acid must be regarded as less than that 

 of the molecules when gaseous, it would appear that it must 

 be greater than that of the molecules when solid — at any rate 

 in such cases where the solid dissolves with an absorption of 

 heat. Thus, in the case of potassium chloride, 74*5 grams of 

 the salt dissolve in water at 0° with an absorption of 5184 cal. 

 Let P and K represent the potential and kinetic energy of the 

 solid (KC1) and of the ions (K + Cl) respectively, then 



P(KCl)+K(K01) = P(K + Cl) + K(K + Cl)-5284cal. 



The kinetic energy of the solid, K(KC1), is possibly an un- 

 known quantity, but it is certainly a positive quantity ; the 



