52 IRON ASSAY. 



yellow color which the solution then acquires is changed 

 to a clear red by adding another drop of the perman- 

 ganate. The number of cubic centimetres of the 

 manganese-solution which have been employed, at once 

 indicates the percentage of iron in the ore. 



Instead of the"crystallized permanganate of potassa, 

 the crude solution originally obtained in the prepa- 

 ration of that salt may be employed, provided it be 

 first graduated that is, quantitatively tested as to its 

 oxidizing power. For this purpose, 3'5 grms. (or half 

 that quantity, T75 grms.) of pure iron-wire are dis- 

 solved in a capacious flask by concentrated hydro- 

 chloric acid, with the aid of heat. The solution is 

 diluted with several times its volume of cold water, 

 and the solution of permanganate dropped into it, as 

 directed above. When the quantity of solution em- 

 ployed has been read off, the whole is diluted with so 

 much water, that 100 cub. cents, may correspond to 3'5 

 grms. of iron. It must be kept in a well-stoppered 

 bottle. 



28. IRON ASSAY. 



The weighed iron-ore, in the state of fine powder, 

 roasted or not, as the case may be, is mixed with dried 

 borax, and the mixture exposed for an hour, in a cov- 

 ered crucible lined with charcoal, to the most intense 

 heat of a wind-furnace with a good draught; the quan- 

 tity of borax varies according to the nature of the 

 iron-ore. The greater the quantity of extraneous mat- 

 ter which is present, the more borax it requires. For 

 10 grms. of iron-ore, 3 grms. of borax may be taken 

 as the minimum, 10 grms. as the maximum. In a well 

 conducted assay, all the iron is found reduced to a sin- 

 gle well-fused button. If the iron ore contained phos- 

 phoric acid the crude iron will contain phosphorus. 



