408 British Association for the Advancement of Science. 



solution of acetate of potash, containing one tenth of its weight of 

 the acetate, is to be added, in the quantity of two hundred grains 

 measured. The mixture, on this addition being made, changes to 

 a dark reddish brown colour, nearly as intense as that of port wine. 

 The mixture is now to be diluted with its own volume of water, and 

 heat applied until it boils; the ebullition continued for about two 

 minutes. The peroxide of iron begins to separate as the heat ap- 

 proaches the boiling-point, and in a short time the whole peroxide 

 is detached. On filtering the mixture whilst hot, the fluid which 

 passes through the filter appears colourless, and on addition of the 

 the triple prussiate of potash, affords neither precipitate nor blue 

 tinge indicating the presence of iron. The powder remaining on 

 the filter, well washed with hot water, is of a clove brown colour. 



The addition of the nitric acid with subsequent ebullition is es- 

 sentially requisite to the success of this experiment; for if the 

 green sulphate of iron be employed without the addition of nitric 

 acid, on adding the solution of acetate of potash, and causing the 

 mixture to boil, no change of colour to reddish brown is found to 

 take place, but a black powder separates, and the mixture when 

 filtered affords a fluid of a strongly ferruginous taste, yielding an 

 abundant precipitate, of a bluish white colour, with the triple prus- 

 siate of potash ; thus proving that the conversion of the oxide of 

 iron into peroxide must precede the addition of the acetate of pot- 

 ash, which is otherwise incapable of separating the oxide of iron 

 from the acid. 



When a solution of the green muriate of iron is treated in a man- 

 ner similar to that above described, by converting the protoxide of 

 iron into peroxide by nitric acid, and decompounding the solution by 

 acetate of potash and heat, the same effects are produced as in the 

 green sulphate of iron. 



If to a solution of peroxide of iron, produced by the method 

 above described, a solution of the oxide of manganese is added, 

 then solution of acetate of potash and heat applied, a similar depo- 

 sition of peroxide of iron takes place ; and the filtered liquor, on 

 addition of triple prussiate of potash, affords a cream-coloured de- 

 posit unmixed with any blue tinge : the peroxide of iron has, there- 

 fore, remained on the filter, and the oxide of manganese in solution 

 has passed through, yielding its proper precipitate with the triple 

 prussiate. It is right to observe, that a solution of the muriate of 

 manganese is not rendered turbid by admixture with acetate of pot- 

 ash and subsequent application of heat. 



It follows from the preceding experiments, which have been many 

 times repeated, that peroxide of iron may be completely separated 

 from either sulphuric or muriatic acid by acetate of potash, and that 

 in a mixed solution of peroxide of iron and oxide of manganese in 

 an acid, a complete separation of the peroxide of iron may be ef- 

 fected by means of the acetate, provided that proper attention has 

 been given to the comparative quantities of the ingredients employed 

 in the mixture. Acetate of soda or of ammonia may be substituted 

 for acetate of potash in producing this decomposition. 



