64 ALUMINOUS CllALYBEATE SPUING IN I. OF WIGHT, 



and -with ^ ue > a g a »n heated to redness, acetic*, instead of nitric acid, 



acetic, W as this time added, and the solution filtered. The filtered 



fluid itill contained a quantity of iron, which, however, 

 v from subsequent examination appeared very inconsiderable, 



and the-hon The oxide of iron left in the filter being roasted with wax 

 seduced. an j neate( j to redness, in order to bring' it to a uniform 



state of oxidation, weighed 6*8 grainsf. 

 Residuum -• With a view to repeat and vary the last ex peri merits 



treated with ano ther portion of residue, also weiohinir 50 grains, wa§ 



carbonate of . . , r> 



*mmonJay thrown into a solution oi neutral carbonate or ammonia, 

 the quantity of the latter being more than sufficient to sa- 

 turate any acid present, and to dissolve the magnesia sus- 

 pected to exist in that residue. A considerable efferves- 

 cence took place. The mixture, after this, was gently 

 heated and filtered. The residue left in the filter was of a 

 the filtered pale yellowish brown colour. The clear solution deposited 

 mutter treated a small quantity of precipitate similar to the residue left in 

 ' the filter, to which residue this precipitate was added. The 

 contents of the filter were then trfated with potash, in the 

 manner before described (sect. VIII, li), in order to sepa- 



* The acetic acid, as well as the nitric, is said to be incapable of dis* 

 *>lving any iron, which has been peroxidated by the process just de- 

 scribed. In this instance a few particles of oxide were taken up by 

 the acid: but it is probable, that if, instead of healing the residue to 

 redness only a few minutes, the oxide had continued ixposed to a rod 

 heat fur half an hour or more, the whole of it would have become in* 

 soluble. 

 „ , f Tt maybe asked, in what state of oxidation the iron is after this 



«xide^ operation ? It has generally been supposed to be reduced to the state of 



protoxide in consequence of the affinity of the combustible matter for 

 oxigen ; but in an experiment, which 1 made some years ago to ascer- 

 tain this point, (the particulars of which maybe seen in my account 

 of the Brighton chalybeate) this process appeared to bring the iron to 

 ♦he state of peroxide; for 100 parts of iron gave 147 6 parts of oxide, pro- 

 portions which are now considered as constituting the red oxide of iron. 

 And as a confirmation of this, I observe, that Dr.Thomson,in his valu- 

 able paper on the oxides of iron, published in the twenty-seventh vo- 

 lume of Nicholson's Journal, states (p. 3/9) that some of the red oxide 

 being mixed with oil and heated to redness, till it became black and 

 magnetic, no diminution of weight took place. Indeed 1 have always 

 obtained by this process, not a black, but a brown oxide, which in cooling 

 passes to a red brown colour, somewhat varying in shade, but mostly 

 resembling powdered cinnamon, and being more or less magnetic. 



rate 



