178 Mr. V. H. Veley on the Phases and 



dissolved potassium chloride is considered to be free, or at 

 least not combined with the potassium. Williamson pointed 

 out years ago that it is not strictly accurate to speak either of 

 the element potassium or the element chlorine as present in 

 potassium chloride, and, indeed, there is a certain inconsistency 

 in modern nomenclature in that one element and not the other 

 is put in the adjectival form. 



It can be argued that an asymmetric carbon atom is like- 

 wise a mental abstraction; but specific attributes are not 

 predicated of such a carbon atom — all that is or can be done 

 is to put forward this abstraction as a working hypothesis to 

 explain the constitution of certain carbon compounds. Mole- 

 cules also are ideals, but we cannot predicate of them any 

 attributes, whether of sphericity or non-sphericity, of elasticity 

 or inelasticity : as we may apply the ideal geometrical tri- 

 angle for the more real triangle of velocities, so likewise we 

 apply our ideal molecules to solve problems on the velocities 

 of congeries of them. 



But certain writers incline to draw students away from the 

 main issue by a distinction between heat-dissociation and 

 ionic or electrolytic dissociation (both terms being unfortunate 

 enough). Thus to select a case, these statements are made 

 equally as of matters of fact*: — " If sal ammoniac is dissolved 

 in a large quantity of water it is electrolytically decomposed 

 almost completely in accordance with the equation 



NH 4 C1=NH 4 + C~i, 



and if we vaporize it under sufficiently low pressure, it 

 decomposes again in accordance with the equation 



NH 4 C1=NH 3 +HC1, 



viz. in unelectrified molecules. Both are quite different phe- 

 nomena^ the interdependence between which, even if probable, is 

 not yet known." 



The former reaction is, however, quite theoretical, and we 

 have no manner of means of identifying the presence of the 

 hypothetical radical, NH 4 , or the electro-negatively charged 

 elementary substance chlorine, possessing hypothetical pro- 



* The original is here appended : — " Lost man Salmiak in viel "Wasser 

 auf, so dissociirt er sich fast yollig in Sinne der Gleichu^g . . . electro- 

 lytisch, und vergasen wir ihn unter hinreichend kieinem Drnck, so zer- 

 fallt er wiederum sehr weit gehend in Sinne der Gleichung ... in uu- 

 electrische Molecule. Beide sind ganz verschiedene Vorgange, zwischen 

 denen ein Zusammenhang , wenn er audi wahrscheinlich, so dock nicht 

 erkannt ist" Nernst, cf. supra. 



