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



The first view is based upon the analogy of the solution of 

 certain metals in sulphuric acid, whereby hydrogen is set free, 

 and also upon the argument that this same gas is set free, when 

 metallic magnesium is dissolved in nitric acid ; but it appears 

 that, if we accept this view, a certain property, namely that of 

 reducing nitric acid, is attributed to the element hydrogen when 

 in a certain condition (to which also is superadded a current- 

 energy), which it does not possess in the state or condition in 

 which we know it. The general conception is that the element 

 hydrogen in the former case is " atomic " and in the latter is 

 " molecular," though it is to be observed that the relations of 

 atoms to molecules are in obscurity. That is to say, four distinct 

 hypotheses are involved: — (i.) that of nascent hydrogen ; (ii.) 

 that nascent hydrogen is atomic ; (hi.) that nascent or atomic 

 hydrogen differs in its attributes from hydrogen as we know it; 

 and (iv.) that hydrogen, as we know it, is molecular. Further, 

 it does not seem safe to argue from the reaction of magnesium 

 with nitric acid to those of copper &c. with the same acid, for 

 at present there is no evidence to show that the solution of 

 magnesium in the acid is dependent upon the presence of 

 nitrous acid. If this is shown not to be the case, cadit qucestio. 



The often-cited argument in favour of the nascent hydrogen 

 hypothesis, namely, that no reduction ensues when hydrogen 

 gas is passed through nitric acid, appears to be rather beside 

 the question, for on the one hand the contact between a gas 

 and a liquid is very incomplete, only the outer shell of each 

 bubble being affected, and on the other the stream of the gas 

 would mechanically blow off any nitrous acid (or nitrogen 

 peroxide) which might be formed. 



The argument from the reactions supposed to take place in 

 the Grove's cell seems also to be beside the point, since there 

 must be a certain amount of interdiffusion between the nitric 

 and sulphuric acids which would complicate the chemical 

 changes. But, on the other hand, the following facts support 

 the view that the nitrous acid or nitrogen peroxide is 

 formed initially from the nitric acid per se : — First; the 

 more concentrated acid very rapidly turns yellow from the 

 formation of nitrogen peroxide, when exposed to the sun- 

 light, but more slowly when the acid is kept in the dark 

 or diluted. Further, my experience has shown that even 

 the jolting of a railway journey is sufficient to increase the 

 proportion of the nitrous compound even in the case of acids 

 of about 30 per cent, concentration. Secondly, the same 

 change is very readily effected by the presence of organic 

 matter, which it is well-nigh impossible to eliminate from the 

 air of laboratories. 



