. Journal. erly preparedwere Roman alunitc and alum shale, both of which wereroasted, the former yielding alum at once, the latter afteraddition of potassium sulphate. The percentage of alu-minium sulphate in the alum obtained from the shalecould not be determined from its density, on account ofthe large quantity of sulphate of iron present, and thestrength of the alum was calculated from Ioggiales tablesof solubility of potash alum. Now, however, alum andaluminium sulphate are usually prepared by treatingbauxite and alunite with sulphuric acid. Bauxite yieldsa very pure aluminium sulphate, an
. Journal. erly preparedwere Roman alunitc and alum shale, both of which wereroasted, the former yielding alum at once, the latter afteraddition of potassium sulphate. The percentage of alu-minium sulphate in the alum obtained from the shalecould not be determined from its density, on account ofthe large quantity of sulphate of iron present, and thestrength of the alum was calculated from Ioggiales tablesof solubility of potash alum. Now, however, alum andaluminium sulphate are usually prepared by treatingbauxite and alunite with sulphuric acid. Bauxite yieldsa very pure aluminium sulphate, and alunite a concen-trated solution of alum in aluminium sulphate, the latterbeing left behind in an almost pure state after crystalli-sation of the alum. The anthor gives tables representingthe densities of solutions of pure and commercial alumi-nium sulphate, containing from 1 to 25 per cent, ofsulphate, and at temperatures 15°, 25°, 35Q and 45 . At15° be finds the density of the pure solution to be re-. the hot gases from 1! led away through Q for purposesof evaporation. The lumps of partially dried carbonateare allowed to fall in from X, steam being introduced at!•, superheated by passing through (, and liberatedcarbonic acid passing away through L. The strontiumoxide formed is removed at the bottom of the furnacethrough doors II into waggons J. Afresh quantity ofcarbonate, equal to that removed at II, is introducedfrom X. the retorts in their turn being filled up. Theprocess i-- thus practically continuous. Sight holes K are provided at intervals. Im separating the excess ofstrontium hydrate from the mother-liquors obtained in presented by the equation d=r007 + 0 01;», where p =percentage of pure anhydrous aluminium on the solubility of alum in solutions of aluminium sulphate were made by adding 4, 3, 2 anil 1per cent, respectively of anhydrous potassium sulphateto solutions of aluminium sulphate of various strengths,beating the mixture to SO ami
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectchemist, bookyear1882
