of the Elements. 439 



its compounds present some analogy to those of the secondj and 

 still more to those of the fourth group. Solid carbonic acid, 

 obtained by cooling the liquid, is a transparent glassy substance 

 resembling fused boric acid. The bichloride of carbon, CCl'*, is 

 comparable to the chlorides of silicon and tin, SiCl* and SnCl'', &c. 

 The elements fluorine, oxygen, nitrogen and carbon, which would 

 thus stand at the head of the four groups, present a curious nu- 

 merical sequence : — 



C = 12 forms H^C 5 vols. = 2 



N = 14 ... H^N 4 vols. = 2 



O = 16 ... H^O 3 vols. = 2 



F = 18? ... HF 2 vols. = 2 



It is observable that the monhydrides are powerful acids, the 

 binhydrides somewhat neutral bodies, and the terhydrides rather 

 alkaline than otherwise. Similar relative differences in character 

 may be traced to a certain extent in their corresponding deri- 

 vatives. 



In all four groups a gradual development of metallic charac- 

 ters accompanies the increase in atomic weights, illustrating 

 foi'cibly the extremely artificial character of the division of the 

 elements into metallic and non-metallic bodies. In the several 

 groups to be subsequently considered, we do not find the perfec 

 tion of metallic character pertain to those members which have 

 the highest atomic weights. 



It is interesting to observe, that by the use of more or less 

 empirical seriated formulae, and by a recognition of chloro- 

 derivatives in mineral as well as in organic chemistry, it is pos- 

 sible to manifest clearly the really simple relations which subsist 

 between the members of the different groups, and to reduce to 

 an orderly position numerous bodies generally considered ano- 

 malous; as is the case, for instance, with kakodylic and stibtri- 

 ethylic compounds*. Remembering the greater development of 

 basylous characters in arsenic and antimony than in nitrogen 

 and phosphorus, the compounds of kakodyle and stibtriethyle 

 are strictly comparable, not only in formulae but in properties, to 

 their normal azote and phosphoi-us congeners. 



* Vide Cavendish Society's translation of Laurent's 'Chemical Method,' 



E, 278 et seq., to learn the ingenious contrivances that were resorted to by 

 aurent for o])viating the anomalies presented by the kakodylic and stib- 

 ethylic compounds. 



