Red Solutions of Manganese. 55 



3dly, the formation of these oxides may be accounted for by 

 supposing the peroxide reduced to protoxide, portions of 

 which become again oxidized by oxygen evolved from other 

 portions of peroxide. Since the affinities of these oxides are 

 admitted to be so much inferior to the protoxide, which, with 

 acids, produces definite and permanent compounds, it is not to 

 be expected, therefore, that either the red or the deutoxide 

 should alone be produced ; and in the second, which is the 

 simplest case of the action of sulphuric acid, where, by the 

 loss of one proportional of oxygen, a protoxide is produced to 

 form the constant base of the sulphate, there is no reason to 

 suppose that another oxide should be formed at the same time, 

 and held in solution by the same acid, but with which it is 

 admitted that it cannot form salts; on the third view, the effect 

 of additional oxygen, combining with the protoxide, would be 

 to produce another oxide, acknowledged to have much less 

 affinity for the acid than the protoxide, which, in fact, is to 

 suppose that a weaker could subvert a stronger affinity, and 

 that the feeble indefinite combination resulting (so feeble that 

 even water can destroy it) could hold the place of a strong, 

 definite, and neutral compound with the same acid. Even 

 admitting that protoxide of manganese could combine with 

 oxygen to form a coloured state, this notion would certainly 

 be in favour of manganesic acid. So I suppose that protoxide 

 is present in the red solutions; and it will presently appear that 

 manganesic acid and protoxide may be in solution together. 



On the supposition heretofore entertained, that an oxide 

 is the cause of colour in the red fluids, it has not been 

 stated whether this oxide be alone or with protoxide ; but it 

 has been admitted that when a red solution by decomposition 

 precipitates a dark oxide, that much protoxide remains behind 

 in solution *. Then this precipitate evidently does not contain 

 the whole, or the same proportion of metal and oxygen which 

 existed in the red solution. It has also been considered that 

 the colour was due to the oxide thrown down ; and as no mode 

 has ever been pointed out for separating protoxide only, it fol- 

 lows, that when the manganese is precipitated from a crimson 



* ' 3 grains of peroxide were precipitated, and after the action of water potash 

 threw down 27 grains of oxide.' Phillips, Phil. Mag., N, S. ; v, 216. 



