386 



On Antimony Pentachloride. 



[June 16,. 



most simply to explain the formation and decomposition of this new 

 componnd : — 



COOSbCl* 



I. I 



COOSbCl 4 



oxalic acid in which the hydrogen atoms are replaced by the univalent 

 radical Sb'Cl 4 . Considering the fact that the compound does not 

 unite with a second molecule of oxalic acid, the formula — 



COO v 



IT. | >SbCl 3 SbCl 5 

 COCK 



does not seem at all probable. According to formula I. one can 

 compare the compound with diammonium oxalate, and designate it as 

 ditetrachlorstibonium oxalate, or as we prefer, look on it as the- 

 mixed anhydride of oxalic acid and the yet unknown acid, SbCl 4 OH. 



As a result of these simple experiments we can understand the* 

 entirely different behaviour of antimony and phosphorus penta- 

 chlorides towards the carbon compounds containing oxygen and 

 hydrogen. Antimony pentachloride unites, as we have proved, witb 

 water. Phosphorus pentachloride decomposes water. Antimony 

 pentachloride has no inclination to change chlorine for oxygen. Phos- 

 phorus has this inclination in an extraordinary degree. Phosphorus 

 pentachloride attacks hydroxyl or ketone groups, replacing oxygen 

 by respectively one or two atoms of chlorine, being itself converted 

 into oxychloride. Antimony pentachloride, on the other hand, reacts 1 

 on the hydrocarbon residue, substituting chlorine for hydrogen, and 

 itself becoming antimony trichloride. 



Phosphorus pentachloride acts similarly to antimony pentachloride, 

 substituting chlorine for hydrogen in those organic compounds which 

 contain no oxygen, or oxygen in such firm combination with carbon 

 as not to be available for the formation of phosphorus oxychloride. 



Antimony pentachloride may react as phosphorus pentachloride on 

 compounds similar to oxalic acid, containing no hydrogen attached 

 to carbon which can be replaced by chlorine. The compound 

 (COOSbCl 4 ) 2 is of especial theoretical interest, as showing the- 

 process of the reaction of phosphorus pentachloride on substances 

 containing the hydroxyl group. The first stage of the reaction con- 

 sists, evidently, of the formation of compounds analogous in com- 

 position to the body (COOSbCl 4 ) 2 - 



If, however, the oxygen of a hydroxyl group is held in loose com- 

 bination, the formation of phosphorus oxychloride and the substitu- 

 tion of chlorine take place simultaneously. What, however, will 

 happen when the substitution of oxygen is difficult, as in phenol or 

 the aromatic oxyacids ? Attempts to answer this question are now 



