A DREAM OF FAIR HYDRONE 493 



possible to obtain different derivatives according as this 

 hydrogen atom or one of those in ammonia were displaced by 

 some equivalent radicle such as methyl. Calling the three 

 hydrogen atoms in ammonia a b c and that in hydrogen chloride d, 

 if the four atoms of hydrogen abed in ammonium chloride 

 be of equal value, it should not matter in what order they are 

 displaced. If, however, d be different from abc and different 

 radicles were introduced in place of the four hydrogen atoms at 

 one time in one order and at another time in another, the result 

 would be different. A large number of such substituted 

 ammonium compounds have been prepared, but in no case has 

 any such difference been met with. It is therefore assumed that 

 in ammonium chloride the four hydrogen atoms are of equal 

 value and symmetrically distributed about the nitrogen atom 

 and the associated negative radicle. 



In the case of ammonia itself, the functional identity of the 

 three hydrogen atoms has been established beyond question by 

 preparing from it substituted ammonias by introducing three 

 different radicles a b c in place of its three hydrogen atoms. 

 Whatever the order in which the radicles are introduced, 

 whether it be 



abc acb bac bca cab cba 



the product eventually obtained is always one and the same 

 substance. 



But this conclusion — that when hydrogen chloride and 

 ammonia interact a re-arrangement takes place as the result of 

 the separation and independent association of the elements of 

 the hydrogen chloride molecule with the nitrogen atom of the 

 ammonia molecule — has far-reaching consequences if the argu- 

 ment be extended to the other cases under consideration. 



Then it may be asked, What happens when ammonia is 

 brought into contact with water ? It is clear that the two 

 compounds interact in some way. Is the behaviour of hydrogen 

 oxide towards ammonia in any way similar to that of hydrogen 

 chloride ? It may be supposed that, like this latter, it is 

 divisible into two radicles, H and OH. Is it so divided and do 

 these radicles enter separately into combination with the 

 nitrogen atom, forming ammonium hydroxide, NH 4 .OH? 

 Since ammonium chloride is the analogue of sodium chloride, 

 ammonium hydroxide should be very similar to sodium 



