58 Mr. T. J. Pearsall on the 



and colourless protosulphate of manganese ; both were of 

 similar temperature and density ; they produced a clear bright 

 red solution when put together, which, by dilution with 

 water, decomposed, and appeared of an amber tint by the 

 separation of oxide. Protosulphate of manganese may be 

 added to red manganesate of potassa and sulphuric acid 

 without any immediate precipitation. The triple sulphate of 

 ammonia and manganese, when acid, was rendered pink by 

 manganesic acid. The existence of manganesic acid in fluids 

 containing protoxide, at once explains the origin of the rose 

 tints observed in the salts of manganese. 



These experiments relative to the addition of manganesic 

 acid to the ordinary red solutions, show that the mixture exhi- 

 bits the same colour as a solution of the same depth of tint, 

 either of sulphuric acid and red manganesates, or of the ordi- 

 nary red sulphate ; but the properties so communicated in this 

 case clearly depend upon the known state of manganese, and 

 therefore the evidence is much strengthened in favour of the 

 opinion that the whole of the phenomena of all red solutions 

 of manganese are due to manganesic acid. 



Having thus found that manganesic acid could do all that 

 the red solutions performed, I endeavoured to obtain the acid 

 itself from solutions formed in the usual mode, by acid and 

 oxide; and as manganesic acid is capable of existing in a 

 state of vapour, I hoped, if it were present, that a small por- 

 tion might be volatilized by distillation. I had previously 

 found that the bleaching alkaline chlorides could hold manga- 

 nesic acid in solution ; very many distillatory experiments were 

 therefore made with the very deeply coloured red sulphate, and 

 in some of them it appeared as though manganesic acid was 

 driven over into the receiver, for a solution of indigo was 

 bleached ; and even the acid itself, by its pink tints and other 

 properties, was evident in the solution of chloride, which re- 

 ceived the extremity of the retort. These results became 

 doubtful, when it was afterwards found that certain proportions 

 of acid protosulphate of manganese when mixed with a solu- 

 tion of bleaching chloride of soda formed manganesic acid. 

 The experiments were therefore repeated with a retort having 

 a long neck, which was bent several times in order to collect 



