Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/239



1. Fifty grains of residue dried at the temperature of between 170 and 180, (as described in § VI.) and therefore equal to ten ounces of the water, were boiled in successive solutions of potash, so as to saturate all the acid contained in that residue, and to dissolve the alumine. The remaining solid residue (which had passed first to a dark green, and some hours afterwards to a dark brown or nearly black colour) was dissolved in nitric acid and the solution evaporated to dryness, after which a red heat was applied in order to bring the iron to the state of peroxyd, and thus render it insoluble in the same acid. The mass being now treated with nitric acid, in order to separate the lime and magnesia supposed to be mixed with the oxyd of iron, and the whole being thrown into a filter, the clear solution was found still to contain a good deal of iron. This last solution was, like the former, evaporated to dryness, and to the residue, again heated to redness, acetic, instead of nitric acid, was this time added, and the solution filtered. The filtered fluid still contained a quantity of iron, which however, from subsequent examination, appeared very inconsiderable. The oxyd of iron left in the filter being roasted with wax and heated to redness, in order to bring it to an uniform state of oxidation, weighed 6,8 grs.