Red Solutions of Manganese. 57 



of oxygen to become protoxide, whilst two proportionals of 

 oxygen so evolved unite with one proportional of peroxide and 

 constitute manganesic acid, which instantly assumes an inde- 

 pendent existence in the acid solution. 



I have mentioned that the tints are not constantly the same : 

 when oil of vitriol acts upon peroxide of manganese in the 

 cold, the colour, at first pink, becomes ultimately deep crim- 

 son ; a rich scarlet fluid is formed when sulphuric acid acts 

 upon hydrated brown oxides ; and I have also observed, where 

 excess of oxide has been employed, that the subsequent addi- 

 tions of acid were paler and pinkish tinted. If strong oil of 

 vitriol be added to the deep crimson solution, the colour 

 changes to pink or to violet, bordering upon purple : on con- 

 centrating the same deep red solution by heat, it changes to a 

 pink tint. These variations are enumerated to show that no 

 arguments can be raised against manganesic acid on the point 

 of colour : for these colours are identical with those exhibited 

 by manganesic acid and manganesates under different circum- 

 stances. 



Assuming that manganesic acid gave colour to the red sulphuric 

 acid, then the addition of manganesic acid should increase the 

 colour and other properties ; and it was found that manganesic 

 acid added to pink sulphuric acid decanted from an oxide, 

 immediately heightened the brilliant pink tint, giving deep 

 colour without any other change. After the fluid had been 

 kept three months in a stopped bottle, the pink colour still 

 remained stronger than that of the acid originally employed. 

 The red manganesate of potassa, with sulphuric acid, was also 

 mixed with another portion of the same solution ; the colour 

 was increased to crimson ; and although oxide of manganese 

 was deposited upon the glass after some days, the tint still 

 remaining was stronger than that of the acid in contact with 

 oxides. A portion of the red sulphuric solution was decom- 

 posed by adding six times its bulk of water ; dark brown oxide 

 was separated ; and the clear fluid evaporated to its former 

 bulk ; then red chamelion of potassa restored the red colour, 

 which appeared exactly like that of the original fluid when 

 they were compared. Two mixtures were prepared one of 

 sulphuric and manganesic acids, the other of sulphuric acid 



