50 WET ASSAY OF IKON. 



mina and part of the phosphoric acid, which are sepa- 

 rated as in No. 19. 



The precipitate, consisting of proto-sesquioxide of 

 iron, carbonate of protoxide of manganese, carbonate 

 and phosphate of lime and magnesia, is dissolved in 

 hot nitric acid; the solution is neutralized, as far 

 as possible, with carbonate of soda, mixed with acetate 

 of soda, and boiled, when all the phosphoric acid and 

 sesquioxide of iron are precipitated. In order to sepa- 

 rate these, the precipitate is treated as in No. 22. 



The filtrate contains the protoxide of manganese, 

 lime, and magnesia, which are separated as in No. 25. 



27. WET ASSAY OF IRON. 

 (Volumetric Method.) 



The process for determining in the moist way with 

 great accuracy, and without a complete analysis, the 

 amount of iron contained in an ore, consists in ascer- 

 taining the number of measures of a solution of per- 

 manganate of potassa of known strength which may 

 be decolorized by the solution of protoxide of iron 

 obtained from a given quantity of the ore.* 



One equiv.= 1/980 grms. of crystallized perman- 



r * To prepare the permanganate of potassa, 10 parts of very finely 

 powdered pyrolusite are mixed with 7 parts of chlorate of potassa, 

 the mixture saturated with a very concentrated solution of 10 parts 

 of hydrate of potassa and the wet mass gradually heated in an 

 earthen crucible to dull redness, so that it cinders together, but 

 does not fuse. When cool, it is powdered, treated, in a flask, with 

 a considerable quantity of hot water, and washed carbonic acid 

 gas passed into it until the color of the solution has changed to a 

 purple-red, and the excess of potassa is converted into the carbo- 

 nate. It is then allowed to stand until the solution becomes clear, 

 which is poured off from the precipitate and evaporated to the 

 point of crystallization. The salt is then purified by recrystalli- 

 zation. 



