Red Solutions of Manganese. 51 



and the fluid in the retort still strongly bleached indigo ; but 

 when a small portion of solution of chlorine was added to the 

 same crimson fluid, or to colourless protosulphate of manga- 

 nese, and then heated in the same manner, chlorine was driven 

 over, and rapidly bleached the blue liquor. If chlorine, there- 

 fore, had been present in the previous experiments, it would 

 have been rendered evident by this arrangement. 



In other experiments the crimson sulphuric acid solution 

 was decomposed by being much diluted with water, the oxide 

 separated by filtration, and the clear liquor distilled ; half the 

 fluid, however, passed over into the indigo without effecting 

 any bleaching change, nor did the liquor in the retort bleach : 

 if chlorine had been present in the solution, it would have 

 remained after dilution. 



Then pure hydrated protoxide of manganese, which had be- 

 come brown by exposure to the air, was mixed with sulphuric 

 acid, and a red fluid was obtained which possessed bleaching 

 properties, but which, when diluted with water or heated with 

 alcohol, lost all colour and all bleaching power : hence there 

 is no evidence that chlorine is the bleaching agent; on the con- 

 trary, the bleaching power of the sulphuric solutions accompa- 

 nies the coloured state of manganese, and it appears that these 

 two properties are present or absent together. 



As the red sulphuric solution appears to have been the 

 only one referred to with regard to this power, I proceeded to 

 examine whether other red solutions of manganese possessed 

 similar properties. 



In the process of triturating together binoxalate of potassa 

 and peroxide of manganese, pointed out by Van Mons*, a 

 crimson fluid is produced of great depth of colour; it is acid, 

 and becomes colourless after some time, depositing crystals. 

 I found that while red it bleached indigo very strongly, the 

 action being accelerated by the addition of sulphuric acid. 



This crimson solution lost its colour when heated in a retort; 

 carbonic acid gas was evolved, which bubbled through the 

 solution of indigo, without altering it, and the fluid in the 

 retort, now clear and colourless, had lost its bleaching power. 



* Quarterly Journal of Science, ix. 409. 



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