Red Solutions of Manganese. 59 



any acid fluid during the distillation ; and according as greater 

 precautions were taken, slighter indications of manganesic 

 acid were obtained ; but as the hot fluid which collected in 

 the angles would obviously tend to absorb and interfere with 

 any small portion of volatile matter from the body of the 

 retort, and as the length of transit was also increased, under 

 these circumstances no conclusion can fairly be drawn either 

 way. While the above experiment throws doubt upon the 

 results of vapourizing the crimson fluid, yet it establishes the 

 fact, that manganesic acid is produced when oxides of man- 

 ganese are in solution with substances evolving oxygen, and 

 therefore supports the particular view I have taken*. 



Experimental comparisons were then made between the 

 red solutions and those containing manganesic acid, with 

 regard to other properties ; but the presence of protoxide of 

 manganese in the red solutions, and the great excess of acid, 

 are circumstances which interfere with and modify the results 

 obtained by the action of some tests, for as yet no process hag 

 been devised for separating protoxide or the proto-salts. 



Solution of green chamelion of potassa and oxalic acid 

 formed a deep red solution, as also did red manganesate of 

 potassa and binoxalate of potassa. Green manganesate of 

 baryta and binoxalate of potassa produced a rich red solution. 

 These were compared with the crimson fluid from a mixture of 

 binoxalate of potassa and peroxide of manganese. All these 

 solutions became colourless in some hours' time, and in con- 

 centrated solutions deposited white crystals. They are all 

 rendered colourless by heat. Ferro-prussiate of potassa gave in 

 all a peculiar yellow-green precipitate ; hydriodate of potassa a 

 reddish-amber tint in all. Red ferro-prussiate of potassa occa- 

 sioned in the whole a similar red brown turbidness ; by trans- 

 mitted light the edges appeared greenish. With tincture of 

 galls all these solutions became colourless, and deposited light- 

 brown oxide. Proto-muriate of tin rendered them colourless, 

 and precipitated minute white crystals. Sulphuretted hydrogen 

 destroyed colour in all, and rendered them turbid. Caustic 



* Dr. John described the fact of the volatilization of manganese by distillation 

 some years before manganesic acid was known ; but he supposed it to be a new 

 or different body, and remarks that the experiments must be made upon some 

 pounds of the ore at once, Annals of Philosophy, ii. 270. 



