82 Examination of the Peroxide of Manganese. 



had not time to pursue them far enough to afford any very defi- 

 nite result. They may however serve to point the way to some 

 one who has sufficient zeal for the science, to carry them out to 

 some more useful end than I could hope to attain. I must here 

 make my acknowledgments to Prof Booth, in whose laboratory, 

 and with whose assistance, these examinations were made. 



The peroxide of manganese has never been investigated, as 

 its existence has until lately been questioned by some of the first 

 chemists in Europe, and the tendency of its salts to convert 

 themselves into proto-salts, contributed to render it problematical 

 whether it was not merely the protoxide disguised. It can be 

 obtained in various ways, but the most convenient is to calcine 

 the proto-nitrate gently until the nitrous acid ceases to be given 

 off. A less troublesome method is to heat the common black or 

 deutoxide, until part of its oxygen is given off, but this method is 

 uncertain, as too great a heat converts it into the manganoso- 

 manganic oxide, and it is almost impossible to obtain the black ox- 

 ide free from admixture with iron. When obtained by calcining, 

 its color is of a deep black, and sometimes shining; but when 

 precipitated from a liquid, as the permanganate of potassa, it is of 

 a dark brown. It has sometimes been found native, and is then 

 known to mineralogists under the name of Braunite. It unites 

 with water and forms the hydrate, which may be readily produ- 

 ced by precipitating the hydrated protoxide from a proto-salt, and 

 exposing it to the action of the atmosphere. Obtained in this 

 manner it appears under the form of a brown powder, but when 

 found native, it is black and crystallizes sometimes in acicular 

 crystals, and sometimes in octahedra, resembling in this state the 

 deutoxide. The peroxide is composed, according to the calcu- 

 lations of Berzelius, of 43.37 of oxygen to 100 of manganese. 



With the different acids it has very various actions ; with some 

 it is converted into protoxide, forming proto-salts ; while with 

 others it immediately forms per-salts, which seem to have no reg- 

 ular color, some being red, while others are nearly white, brown, 

 or yellowish ; a dirty white is however the most usual appearance. 

 I have found it to be the case, that most vegetable acids which 

 convert the peroxide into protoxide by giving off oxygen, when 

 acting upon the deutoxide, will form per-salts by the loss of oxy- 

 gen. They all contain a very great excess of acid, without the 

 presence of which the peroxide seems incapable of forming any 



