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



when moist *, as compared with their inertness when dry. 

 The non-combustibility of charcoal, sulphur, and phosphorus 

 in oxygen, the non-combination of ammonia with hydrogen 

 chloride, the inappreciable change when undiluted acids are 

 poured upon carbonates, and a host of other examples might 

 be cited. Upon this point Ostwald, on the one hand, appears 

 to beg the whole question when he writes that, u as probably 

 there is no absolute non-conductor, there is the possibility in 

 all cases of assuming the existence of at least a few ions.''* 

 On the other hand, Armstrong would assign to " water special 

 properties which enable it to act directly ; moreover — perhaps 

 because — in such cases composite electrolytes would result." 

 On both sides, be it noted, we are asked to be content with 

 mere possibilities, which are even more unsatisfactory in the 

 science of chemistry than they are in matters of real life. 



As yet there seems to be no answer forthcoming to the 

 question, Why does chemical change ever begin ? 



The Reaction of Acids with Metals. 



The particular case of these reactions I have proposed to 

 consider separately, partly on account of its practical im- 

 portance, partly also to deal with another " eidolon " of 

 chemistry, nascent hydrogen, and lastly because I have been 

 more specially interested with the problem. In former years, 

 and possibly even to this day, it was customary to teach that 

 both zinc and copper, for example, directly displace hydro- 

 gen from sulphuric acid ; but in the first case the gas is 

 liberated as such, while in the latter it is nascent and reduces 

 the sulphuric acid to sulphur dioxide. So also the more 

 complicated results of the reaction of metals with nitric acid 

 have been supposed to be the successive products of the 

 reduction of the acid by nascent hydrogen of greater or less 

 activity. 



As to the latter problem, and more especially with regard 

 to the metals silver, copper, mercury, and bismuth, it was 

 originally shown by Millon | for the first three metals, subse- 

 quently more completely by Russell J for silver, and finally by 



* Apart from the Baconian maxim, " Corpora non agunt nisi soluta," 

 the following passage shows that the necessity of water for chemical 

 change had been the subject of observation even at the commencement of 

 the present century : — " Pure calcareous earth (lime) will have no effect 

 on muriatic gas when both are perfectly dry ; yet water, to which the 

 gas has no chemical am uity, will condense it : in this state it will readily 

 form an intimate union with the lime " (Higgins, ' Experiments and 

 Observations on the Atomic Theory,' 1814). 



t Comptes Rendus, xiv. pp. 904-912. 



\ Journ. Ohem. Soc. 1874, pp. 3-12. 



