THE TABLE OF THE LAW. 



31 



A glance at this table shows their striking similarity of 

 behaviour, even in the most varied properties. This simi- 

 larity is so great that in general terms, x may be written, 

 standing for either calcium, strontium or barium, in any 

 chemical reaction. The chief purpose of the diagram, how- 

 ever, is to show that even as they vary from one another, 

 they vary progressively and in definite steps. Notice in the 

 diagram that as the atomic weight rises, so does the specific 

 gravity, the temperature at which their carbonates dissoci- 

 ate, the solubility of their hydroxides, and the heat of forma- 

 tion of their chlorides. 



Suppose, now, we take another group, say Group VII, 

 known as the family of the Halogens. This group consists, 

 as usual, of two sub-groups: 



Sub-group A. 

 Fluorine 

 Chlorine 

 Bromine 

 Iodine 



Sub-group B. 

 Manganese 

 Samarium 



