Iron, 



Qf the Analyfis and EJJay of Iron Ores, 

 In the moijt Way. 



41. The general method of analyfing in 

 the moift way the calciform ores, which do 

 not contain much earth or ftony matter, is, 

 after reducing them to a fubtil powder, to 

 diflblve them in the marine acid, and preci- 

 pitate them by the PruJJian alkali ; the quan- 

 tity of alkali ufed difcovers that of iron in its 

 metallic ftate, which the ore would afford, as 

 already mentioned in the analyfis of earths, 

 or the precipitate warned and dried may be 

 weighed ; its weight divided by 6 (fubtrad:- 

 ing 4 per cent, for the iron already contained 

 in the alkali) gives the quantity of iron in 

 its metallic ftate which the ore contains. 



But if the iron be united to any confi- 

 derable proportion of zinc or manganele, its 

 eftimation by the above methods is not fuSU 

 ciently accurate ; therefore the P ruffian blue 

 muft be calcined to rednefs, and the calx 

 treated with dephlogifticated nitrous acid, 

 which will then take up only the calx of zinc : 

 when this is feparated, the calx mould be 

 again treated either with nitrous acid, with 

 the addition of fugar, or ftill better, with the 

 acetous acid, either of which will feparate 

 f he manganefe, if any ; the remaining calx 



