'I' UK HALOGENS 469 



It is not only hydrocarbons which are subjected to metalepsis. 

 Certain other hydrogen compounds, under the action of chlorine, also 

 give corresponding chlorine derivatives in exactly the same manner ; 

 for instance, ammonia, caustic potash, caustic lime, and a whole series 

 of alkali ' substances. 27 In fact, just as the hydrogen in marsh gas 

 can be replaced by chlorine and form methyl chloride, so the hydrogen 

 in caustic potash, KHO, ammonia, NH 3 , and calcium hydroxide,, 

 CaH 2 O 2 or Ca(OH) 2 , may be replaced by chlorine and give potassium 

 hypochlorite, KC10, calcium hypochlorite, CaCl 2 O 2 , and the so-called 

 chloride of nitrogen, NC1 3 . Not only is the correlation in composition 

 the same as in the substitution in marsh gas, but the whole mechanism 

 of the reaction is the same. Here, also, two atoms of chlorine act : 

 one takes the place of the hydrogen whilst the other is evolved as 

 hydrochloric acid, only in the former case the hydrochloric acid evolved 

 remained free, and in the latter, in presence of alkaline substances, 

 the hydrochloric acid formed reacts on them. Thus, in the action of 

 chlorine on caustic potash, the hydrochloric acid formed acts on 

 another quantity of caustic potash and gives potassium chloride and 

 water, and, therefore, not only KHO + C1. 2 =HC1 + KC10, but also 

 KHO + HC1= H 2 -}- KC1, and therefore the result of both simultaneous 

 phases will be 2KHO + C1 2 =H 2 O + KC1 + KC1O. We will here enter 

 into certain special cases. 



The action of chlorine on ammonia may either result in the entire 

 breaking up of the ammonia with the evolution of gaseous nitrogen, or 

 in a product of metalepsis (as with CH 4 and H 2 O). With an excess 

 of chlorine and the aid of heat the ammonia is decomposed, with the 

 disengagement of free nitrogen. 28 This reaction is evidently accom- 



of methyl chloride, CH 3 C1, or ethyl chloride, C 2 H 5 C1 is capable of substitution ; for 

 instance, glycollic acid, CH 2 (OH)(CO. 2 H), orCO(CH 2 'OH)(OH), was obtained from it, and 

 it appeared that the OH in the group CH 2 (OH) reacted like that in alcohols, and it 

 became clear, therefore, that it was necessary to examine the radicles themselves by 

 analysing them from the point of view of the bonds connecting the constituent atoms. 

 Whence arose the present doctrine of the structure of the carbon compounds. (See 

 Chapter VIII. Note 42.) 



27 By embracing many instances of the action of chlorine under metalepsis we not 

 only explain the indirect formation of CC1 4 , NC1 5 , and C1 2 O by one method, but we alsQ 

 arrive at the fact that the reactions of the metalepsis of the hydrocarbons lose that 

 exclusiveness which was often ascribed to them. Also by subjecting the chemical repre- 

 sentations to the law of substitution we may foretell metalepsis as a particular case of a 

 general law. 



28 This may be taken advantage of in the preparation of nitrogen. If a large excess 

 of chlorine water be poured into a beaker, and a small quantity of a solution of ammonia 

 be added, then, after shaking, nitrogen is evolved. If chlorine act on a dilute solution 

 of ammonia, then the volume of nitrogen doos not correspond with the volume of the 

 chlorine taken, because ammonium hypochlorite is formed. If ammonia gas be passed 

 through a-fine orifice into a vessel containing chlorine, then the reaction of the formation 



