158 Dr TURNER'S Chemical Examination 



manganese and 27.709 of oxygen. According to M. BERTHIER,* 

 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 

 suspects, certainly renders the quantity of oxygen too small; 

 for though, guided by theoretical views, I am disposed to con- 

 sider 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 con- 

 sider the red oxide a compound either of 80 parts or two equi- 

 valents of the deutoxide and 36 or one equivalent of the prot- 

 oxide, as M. ARFWEDSON supposes, or of 44 parts or one equi- 

 valent of the peroxide and 72 or two equivalents of the protoxide 

 of manganese. If, on either of these suppositions, the composi- 

 tion 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 appreciable 

 disengagement of oxygen gas, and the solution is promoted by 

 a slight increase of temperature. If the resulting liquid be se- 

 parated from undissolved oxide, and exposed to heat, its ame- 

 thyst-red tint quickly disappears, and the protosulphate of man- 

 ganese is generated. When the red oxide is briskly heated with 

 sulphuric acid, the protosulphate is formed, and oxygen gas 

 evolved with effervescence. 



On boiling the red oxide with an excess of very dilute sul- 

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



* Annales de Chimie et de Physique, vol. xx. 



