of the Metallic Oxides. 



89 



Relationships of a similar kind, as regards volatility, are 

 observed between the oxides and the chlorides of the bivalent 

 radicals C n H 2w , which are the most analogous to the metals, 

 for example: — 



■< 





Molecular 

 weight. 



Volatility. 



ro 2 H 4 o 



[C 2 H 4 C1 2 ... 

 |0 3 H 6 O 



lC 3 H 6 Cl 2 ... 



f Aldehyde 



44 



99 



58 

 j> 

 >> 

 113 

 >» 



5) 



Boils 21 

 ,, 135 

 „ 60 



h 84 

 ,, 35 



» 47 

 » 56 

 „ 96 

 „ 85 

 „ 70 



^ Ethylene oxide 



f Ethylidene chloride — 



\ Ethylene chloride 



f Propylene oxide 



\ Aldehyde 



[ Acetone 



f Propylene chloride 



\ Propylidene chloride... 

 [ Acetone chl oride 



Let us now attempt, by the aid of this general idea, to 

 determine, a priori, what ought to be the properties of certain 

 particularly interesting oxides. 



To 00 2 , which is gaseous at the ordinary temperature and 

 boils at —78°, corresponds CC1 4 , which is a liquid boiling 

 at +76°. The difference in volatility between the two 

 bodies is 154°. SiCl 4 , TiCl 4 , and SnCl 4 boil respectively at 

 58°, 136°, and 115°. It might therefore be reasonably sup- 

 posed that the corresponding oxides should be eminently 

 volatile. Si0 2 ought certainly to be gaseous at the ordinary 

 temperature, or at least as gaseous as S0 2 , to which it is 

 analogous, and the molecular weight of which is but little 

 different. 



Molecular Boiling- 



weight, point, 



C0 2 . . . . 44 -78 



S0 2 . . . . 64 -10 



Si0 2 .... 60 ■ nonvolatile. 



BC1 3 , with molecular weight 117*5, is a liquid boiling at 

 18°; B 2 3 , wdfh molecular weight 70, ought therefore to be a 

 gas at the ordinary temperature. 



A1 2 C1 6 is a solid, which volatilizes about 100°, and ought 

 therefore to have a corresponding oxide A1 2 3 , if not gaseous, 

 at least very volatile, and the same should hold good as regards 

 Fe 2 3 . 



HgCl 2 (boiling-point 295°) should have a corresponding 

 oxide, HgO (containing a so-called permanent gas in combi- 

 nation with a volatile metal), which, if not gaseous, should at 

 least be much more volatile than HgCl 2 , or metallic mercury. 



