the Ores of Iron, and Crude Iron, 91 



tides. The quantity of peroxide is ascertained in the manner 

 just indicated. To determine the quantity of protoxide the 

 whole of the iron must be brought into the state of peroxide, 

 and from the amount of the peroxide thus olitained must be 

 deducted the quantity of peroxide in the first experiment, and 

 the remainder reduced to the protoxide by calculation. 



The following precautions must be observed in oi'der to 

 obtain accurate results. The copper must be in a state of 

 purity. The hydrochloric acid must be also pure, tolerably 

 concentrated, and employed in excess. Nitric acid should not 

 be used for bringing the iron to the state of peroxide, but either 

 a stream of chlorine, or what is preferable, chlorate of pot- 

 ash. Upon adding the piece of copper to the solution it must 

 immediately be brought to the boiling point, and kept there 

 in order to prevent access of air. Previously to removing the 

 undissolved copper from the solution, hot water is to be added 

 till the vessel is quite full ; this is to be poured off and fresh 

 hot water to be added : the copper, which is generally covered 

 with a brownish coating, is then carefully washed in cold 

 water, dried at a gentle heat, and then weighed. The fore- 

 going process has this advantage ; that the substances ordi- 

 narily met with in iron ores, — such as silica, alumina, mag- 

 nesia, lime, oxide of titanium, oxides of manganese, the phos- 

 phoric and sulphuric acids, &c. — do not in any way interfere 

 with the accuracy of the results. An iron ore containing 

 arsenic, however, cannot be analysed on this principle, as 

 blackish gray scales of arseniuret of copper are deposited on 

 the metallic copper. 



This process is applicable to the examination of cast iron, 

 or iron of other kinds, and also for the comparison of one sort 

 of iron with another. 



Among many experiments which were made, M. Fuchs 

 relates the following. 



Exp. 1. 50 grains of very soft English iron were dissolved 

 in hydrochloric acid, and brought to the state of pei'oxide by 

 chlorate of potash ; 85'8 grains of pure copper were boiled in 

 tliis solution, of which 56"2 grains were dissolved. Therefore 

 as 31-7 : 28 :: 56-2 : 49-46, which is equal to 98*92 per cent, 

 of pure iron; a repetition of this experiment gave 99'19 per 

 cent. 



Exp. 2. 50 grains of pianoforte wires were examined, which 

 indicated 98"75 per cent, of pure iron. The iron in this expe- 

 riment was peroxidized by a current of chlorine; a consider- 

 able deposit of carbon was formed during the process of so- 

 lution in hydrochloric acid, which, however, disappeared upon 

 passing chlorine through the solution. 



