TIIK IIALOfiKNS 463 



not only obtained from chlorine and non-metals, but also from many 

 lower oxides, by the aid of chlorine. Thus, for example, CO, NO, 

 N( ).,, S( ) 2 , and other lower oxides which are capable of combining with 

 oxygen may also assimilate to themselves a corresponding quantity of 

 chlorine. Thus COC1. 2 , NOCL XO 2 C1, SO 2 C1 2 , <fcc., are obtained. They 

 correspond with the hydrates CO(OH) 2 , NO(OH), NO 2 (OH), SO,(OH) 2 , 

 Arc., and to the anhydrides CO 2 , X,O 3 , N 2 A , SO 3 , etc. In this we should 

 evidently see two sides of the matter : (1) chlorine combines with that 

 with which oxygen is able to combine, because it is in many respects 

 equally if not more energetic than oxygen and replaces it in the propor- 

 tion Cl 2 : or (Cl : OH) ; (2) that highest limit of possible combination 

 whicli is proper to a given element or grouping of elements is very 

 easily and often attained by combination with chlorine. If phosphorus 

 gives PC1 3 and PC1 5 , it is evident that PC1 5 is the higher form of 

 combination compared with PC1 3 . To the form PC1 5 or in general PX r ,, 

 correspond PH 4 I, PO(OH) 3 , POC1 3 , tfcc. If chlorine does not always 

 directly give compounds of the highest possible forms for a given 

 dement, then generally the lower forms combine with it in order to 

 reach or approach the limit. This is particularly clear in hydrocarbons, 

 where we see the limit C,,H 2/l+2 very distinctly. The unsaturated 

 hydrocarbons are sometimes able to combine with chlorine with the 

 greatest ease and thus reach the limit. Thus ethylene, C 2 H 4 , combines 

 with CL 2 forming the so-called Dutch liquid or ethylene chloride, 

 C 2 H 4 C1. 2 , because it then reaches the limit C, ( X 2 ,, +2 . In all like cases 

 the combined chlorine is able by reactions of substitution to give a 

 hydroxide and a whole series of other derivatives. Thus a hydroxide 

 called glycol, C 2 H 4 (OH) 2 , is obtained from C 4 H 4 C1 2 . 



In this way chlorine whilst entering with great ease into combina- 

 t ion with simple gases, in a number of cases converts lower forms of 

 combination into higher. Very often chlorine in the presence of water 

 acts directly as an oxidising agent. A substance A combines with 

 chlorine and gives, for example, AC1 2 , and this in turn a hydroxide 

 A(OH) 2 , which on losing water forms AO. Hence the chlorine 

 oxidised the substance A. This frequently happens in the simulta- 

 neous action of water and chlorine: A + H 2 O + C1 2 =2HC1 + AO. 

 Examples of this oxidising action of chlorine may frequently be 

 observed, both in chemical practice and technical processes. Thus 

 chlorine, for instance, in the presence of water oxidises sulphur and 

 metallic sulphides. In this case the sulphur is converted into 

 sulphuric acid, and the chlorine into hydrochloric acid or a metal- 

 lic chloride if a metallic sulphide be taken. A mixture of carbonic 

 oxide and chlorine passed into water gives carbonic anhydride 



