of the Oxides of Manganese. 151 



manganese is composed of 100 parts of the metal and 42'16 parts 

 of oxygen ; but it will appear from the sequel of this paper that 

 the real quantity of oxygen united with 100 parts of manganese 

 to constitute the deutoxide is 42*857 and not 42'16 as ARFWED- 

 SON supposes. 



On the Protoxide of Manganese. 



By this term I mean the salifiable base of manganese, the 

 only oxide of the metal which appears to me capable of forming 

 regular salts with acids. I am of opinion that in this compound 

 manganese is in its lowest degree of oxidation. The existence 

 of the sub-oxides described by BERZEHUS and Dr JOHN of Ber- 

 lin has never been satisfactorily demonstrated ; and I have rea- 

 son to suspect that one or other of them would in some of my 

 experiments have been generated, did there exist any tendency 

 to their formation. 



The protoxide may be formed, as was shewn by M. BERTHIER 

 in the 20th volume of the Annaks de Chimie et de Physique, by 

 exposing the peroxide, deutoxide, or red oxide of manganese to 

 the combined agency of charcoal and a white heat ; and Dr 

 FORCHHAMMER has in the Annals of Philosophy described an ele- 

 gant method of preparing it by means of hydrogen gas at a red 

 heat. ARFWEDSON has likewise had recourse to this method, 

 and I have employed it very extensively during the course of 

 the present investigation. The mode of performing the experi- 

 ment is as follows. The material for yielding the protoxide 

 was either the red oxide, deutoxide, or peroxide of manganese ; 

 and, occasionally, the carbonate was used. When it was wished 

 to employ a red heat only, the material was placed in a small tray 

 of platinum foil, which was introduced into a tube of green glass, 

 through which the hydrogen gas was transmitted. The heat 

 was applied by means of a pan of burning charcoal. To pre- 



