GENERAL OBSERVATIONS. 

 Before decomposition. After decomposition. 



Hydrochloric f Hydrogen ^ Water 



acid \ Chlorine 



Potash (Oxygen , 



I Potassium ____^ Chloride of Potassium. 



In the same manner, peroxide of iron, dissolved in hydro- 

 chloric acid, produces water and a perchloride of iron corres- 

 ponding with the peroxide : 3 H Cl and Fe 2 O 3 =3 H O and 

 Fe 2 C1 3 . And in all cases when a metallic oxide dissolves in 

 hydrochloric acid, without evolution of chlorine, the chloride 

 produced necessarily corresponds with the oxide dissolved. 

 Again, orpiment, or sulpharsenious acid does not combine 

 with potash, when dissolved in that alkaline oxide, but gives 

 rise to the formation of certain proportions of arsenious acid, 

 and sulphuret of potassium : 



Before decomposition. After decomposition. 



Sulpharsenious f Arsenic . ; Arsenious acid. 



acid 13 Sulphur -^.^ 



3 Potash 1 3 p otaggi um _\^ 3 Sulphuret of potas. 



Two pairs of compounds of different series then coexist in the 

 liquid, an oxygen acid, arsenious acid, which unites with the 

 oxygen base, potash, and a sulphur base, sulphuret of potas- 

 sium, which unites with undecomposed sulpharsenious acid. 

 Hence the result of dissolving orpiment in potash is the decom- 

 position of both compounds and formation of two salts of 

 different series, arsenite of potash and sulpharsenite of sulphu- 

 ret of potassium. 



The union of metallic compounds of the oxygen and sul- 

 phur series is a rare occurrence. But the red ore of antimony 

 is such a combination, and oxisulphurets of mercury also exist. 

 Compounds of metallic oxides with metallic chlorides, and with 

 other highly saline binary compounds, are more frequent; 

 but they are not to be placed in the same category with the 

 compounds of individuals both belonging to the same series, 

 which last are neutral salts. For a metallic oxichloride may 

 generally, if not always, be viewed as a chloride to which a cer- 

 tain proportion of metallic oxide is attached, like constitutional 

 water in a hydrated salt. That metallic oxide is likewise al- 

 ways of the magnesian class, or of a class allied to it. Oxichlo- 



