50 Mr. T. J. Pearsall on the 



cover the cause of the colour, and the other properties of the 

 red solutions of manganese, I am led to believe that they are not 

 due to the presence of an oxide, but to manganesic acid, which 

 has not hitherto been suspected *. 



These solutions are always strongly acid; they do not cry- 

 stallize or form definite salts ; the colours and tints are rapidly 

 destroyed by deoxidizing agents, and the concentrated solutions, 

 especially if obtained by means of sulphuric acid, are readily 

 decomposed by mere dilution with water. The solutions have 

 a peculiar odour, and exert strong bleaching powers, which 

 effects have been supposed due to the presence of foreign 

 bodies, rather than to the state of the manganese existing in 

 the solutions. It was necessary, therefore, at first, to ascertain 

 whether these are constant properties of acid red solutions of 

 manganese, or whether they are owing, as supposed, to the 

 action of chlorine derived from accidental sources. 



Black oxide of manganese was repeatedly washed with hot 

 distilled water, which gave no trace of muriatic acid when 

 tested by nitrate of silver ; then oil of vitriol, free from muriatic 

 acid, was diluted with its weight of water and poured upon the 

 oxide. In twenty-four hours the fluid had assumed a crimson 

 colour, and after several weeks a very deep crimson solution 

 was obtained, which, when diluted, produced no turbidness with 

 nitrate of silver. A dilute solution of sulphate of indigo was 

 powerfully bleached by this red fluid, and a stronger solution 

 of indigo had its colour instantly destroyed, leaving only an 

 amber tint. These bleached portions of fluid gave not the 

 least indication of chlorine when tested; but a solution of indigo 

 bleached by chlorine gave a precipitate with nitrate of silver. 

 Part of this red solution was introduced into a retort, the neck 

 of which was dipped into a solution of sulphate of indigo, and 

 the retort heated by a spirit-lamp ; the indigo was not bleached, 

 neither was there any trace of the odour of chlorine ; the ope- 

 ration was continued until part of the contents of the retort had 

 distilled over, the temperature having been raised to about 400. 



The retort was then heated with the neck immersed in a 

 solution of nitrate of silver, in which no cloudiness occurred, 



* Brande's Manual of Chemistry, 3d edit., ii. p, 6, 



