28 Dr. Turner's Chemical Examination 



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 de- 

 scribed by Berzelius and Dr. John of Berlin, has never been 

 satisfactorily demonstrated ; and I have reason to suspect that 

 one or other of them would in some of my experiments have 

 been generated, did there exist any tendency to their forma- 

 tion. 



The protoxide may be formed, as was shown by M. Ber- 

 thier.in the 20th volume of the Annales de Chimie et de Phy- 

 sique, 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 elegant method of preparing it by means of hy- 

 drogen gas at a red heat Arfwedson has likewise had recourse 

 to this method, and I have employed it very extensively du- 

 ring the course of the present investigation. The mode of 

 performing the experiment 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 hy- 

 drogen gas was transmitted. The heat was applied by means 

 of a pan of burning charcoal. To prevent the tube from 

 bending while softened by the heat, two or three pieces of 

 tobacco-pipe were tied to it longitudinally by means of iron- 

 wire. But when it was wished to prepare the oxide at a very 

 high temperature, the material was put into a small tube of 

 porcelain, and then introduced into a gun-barrel which was 

 exposed to a full white heat in a common wind-furnace. A 

 supply of hydrogen gas was procured in the usual manner 

 from zinc and dilute sulphuric acid; but before coming in 

 contact with the oxide of manganese, it was purified by being 

 transmitted through a strong solution of potash, and then 

 dried by the chloride of calcium. At the close of the process, 

 the protoxide was of course preserved in an atmosphere of 

 hydrogen gas until it was quite cold. 



The abstraction of oxygen commences at a temperature be- 

 low that of redness ; and when the peroxide is employed, it 

 becomes red hot by the caloric evolved during the formation 

 of water, considerably before the tray which supports it is 

 rendered luminous by the heat of the fire. It appears never- 

 theless from all my experiments that a strong heat is requisite 

 in order to convert all the red oxide into the protoxide. 

 When the process is conducted at a low red heat, I uniformly 



found 



