THE HALOGENS 475 



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

 hypochlorite, KC1O, calcium hypochlorite, CaCl 2 O 2 , and the so-called 

 chloride of nitrogen, NC1 3 . For 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 T 

 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, 

 it 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 + KC1O, but also KHO + HC1 = H 2 + KC1, 

 and the result of both simultaneous phases will be 2KHO + C1 2 

 c= H 2 O + KC1 + KC1O. We will here discuss 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 ). With an excess of 

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

 disengagement of free nitrogen. 28 This reaction evidently results 

 in the formation of sal-ammoniac, 8NH 3 + 3C1 2 = 6NH 4 C1 + N 4 . 

 But if the ammonium salt be in excess, then the reaction takes the 

 direction of the replacement of the hydrogen in the ammonia by chlorine. 

 The principal result is that NH 3 + 3C1 2 forms NC1 3 + 3HC1. 29 



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, the volume of nitrogen does 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, the reaction of the formation 

 of nitrogen is accompanied by the emission of light and the appearance of a cloud of sal- 

 ammoniac. In all these instances an excess of chlorine must be present. 



29 The hydrochloric acid formed combines with ammonia, and therefore the final result 

 is 4NH 5 + 8C12 = NC1 3 + 8NH 4 C1. For this reason, more ammonia must enter into the 

 reaction, but the metalepsical reaction in reality only takes place with an excess of 

 ammonia or its salt. If bubbles of chlorine be passed through a fine tube into a vessel 

 containing ammonia gas, each bubble gives rise to an explosion. If, however, 



chlorine be passed into a solution of ammonia, the reaction at first brings about 

 the formation of nitrogen, because chloride of nitrogen acts on ammonia like chlorine. 

 But when sal-ammoniac has begun to form, then the reaction directs itself towards 

 the -formation of chloride of nitrogen. The first action of chlorine on a solution of 

 sal-ammoniac always causes the formation of chloride of nitrogen, which then reacts on 

 ammonia thus: NC1 3 + 4NH 5 =N 2 + 8NH 4 C1. Therefore, so long as the liquid is alka- 

 line from the presence of ammonia the chief product will be nitrogen. The reaction 

 NI^Cl + 8C1 2 = N C1 3 + 4HC1 is reversible ; with a dilute solution it proceeds in the above- 

 described direction (perhaps owing to the affinity of the hydrochloric acid for the excess 

 of water), but with a strong solution of hydrochloric acid.it takes the opposite direction 



