of the Oxides of Manganese, S3 



who reduced the red oxide to the metallic state by means of 

 charcoal and a long continued intense heat, the oxygen is only 

 26*6 per cent. But this estimate, as M. Berthier himself sus- 

 pects, certainly renders the quantity of oxygen too small ; for 

 though, guided by theoretical views, I am disposed to consi- 

 der my own number not rigidly exact, yet from the care with 

 which the experiments were made, I am satisfied their result 

 cannot be far from the truth. 



From this proportion of manganese and oxygen, we may 

 consider the red oxide a compound either of 80 parts or two 

 equivalents of the deutoxide and 36 or one equivalent of the 

 protoxide, as M. Arfwedson supposes, or of 44 parts or one 

 equivalent of the peroxide and 72 or two equivalents of the 

 protoxide of manganese. If, on either of these suppositions, 

 the composition of the red oxide in 100 parts be calculated, 

 it will be found to consist of 93*104 parts of the protoxide 

 and 6*896 of oxygen, or of 72*414 parts of metallic manganese 

 and 27*586 of oxygen. These numbers approximate closely 

 to those furnished by my experiments, and may serve perhaps 

 to correct them. 



The red oxide of manganese, when agitated with strong sul- 

 phuric acid, is dissolved in minute quantity, without appreci- 

 able disengagement of oxygen gas, and the solution is pro- 

 moted by a slight increase of temperature. If the resulting 

 liquid be separated from undissolved oxide, and exposed to 

 heat, its amethyst-red tint quickly disappears, and the proto- 

 sulphate of manganese is generated. When the red oxide is 

 briskly heated with sulphuric acid, the protosulphate is form- 

 ed, and oxygen gas evolved with effervescence. 



On boiling the red oxide w T ith an excess of very dilute sul- 

 phuric acid (in the proportion, for example, of two measured 

 drachms of strong acid to five ounces of water), a colourless 

 solution of the protosulphate is obtained ; while a portion 

 of peroxide is left, the quantity of which corresponds to the 

 atomic view just given; that is, 116 parts of the red oxide 

 yield 44 parts of the peroxide of manganese. 



When the red oxide is mixed with strong muriatic acid, a 

 portion of it is almost instantly dissolved, and communicates 

 a deep red colour to the liquid. But the solution is not per- 

 manent. The odour of chlorine is perceptible from the be- 

 ginning, even at a temperature of zero of Fahrenheit ; the dis- 

 engagement of that gas continues slowly, though without di- 

 stinct effervescence, until in a few days the solution, if sepa- 

 rated from undissolved oxide, becomes quite colourless. The 

 red oxide dissolves in hot muriatic acid with effervescence, 

 owing to the evolution of chlorine. 



New Series. Vol. 4. No. 19. July 1828. F On 



