" Tin ores." Boil 100 grains, in a sil ver vessel, with a solution of 600 grains of pure potash. Evaporate to dryness, and then ignite moderately for half an hour. Add boiling water, and if any portion remain undissolved, let it undergo a similar treatment. Saturate the alka line solution with muriatic acid, which will throw down an oxide of tin. Let this be redissolved by an excess of muri atic acid : again precipitated by carbon ate of soda ; and being dried and weigh ed, let it, after lixiviation, be once more dissolved in muriatic acid. The insolu ble part consists of silix. Into the co lourless solution, diluted with two or three parts of water, put a stick of zinc, round which the reduced tin will collect. Scrape off the deposit, wash, dry, and fuse it under a cover of tallow in a cap sule placed on charcoal. A button of pure metallic tin will remain at the bot tom, the weight of which, deducted from that of the ore, indicates the proportion of oxygen. The presence of tin in an ore is indicated by a purple precipitate, on mixing its solution in muriatic acid with one of gold in nitro-muriatic acid.
" Lead ores" may be analyzed by solu tion in nitric acid, diluted with an equal weight of water. The sulphur, if any, will remain undissolved. Let the solution be precipitated by carbonate of soda. If any silver he present, it will be taken up by pure liquid ammonia. Wash off the excess of ammonia by distilled water ; and add concentrated sulphuric acid, applying heat, so that the muriatic acid may be wholly expelled.
" Mercury" may be detected in ores that are supposed to contain it, by distil lation in an earthen retort with half their weight of iron filings or lime. The mer cury, if any be present, will rise and be condensed in the receives..
" Ores of zinc" may be digested with the nitric acid, and the part that is dis solved boiled to dryness, again dissolved. in the acid, and again evaporated. By this means the iron, if any be present, will be renderedinsoluble in dilute nitric acid, which will take up the oxide of zinc. To this solution add pure liquid ammonia, in excess, which will separate the lead and iron, if any should have been dis solved ; and the excess of alkali will re tain the oxide of zinc. This may be se parated by the addition of an acid.
" Antimonial ores." Dissolve a given weight in three or four parts of muria tic, and one of nitric acid. This will take up the antimony, and leave the sul phur, if any. On dilution with water the oxide of antimony is precipitated, and 1 the iron and mercury remain dissolved. Lead may be detected by sulphuric acid.
" Ores of cobalt" may be dissolved in nitro-muriatic acid. Then add carbonate.
of potash, which, at first, separates iron and arsenic. Filter, and add a further quantity of the carbonate, when a grey ish red precipitate will fall down, which is oxide of cobalt. The iron and arsenic may be separated by heat, which volati lizes the arsenic. Cobalt is also ascer tained, if the solution of an ore in muria tic acid give a sympathetic ink. Sec Klap roth's Essays. • To analyze ores in the dry way, a me thod which affords the most satisfactory evidence of their composition, and should always precede the working of large and extensive strata, a more complicated ap paratus is required. An assaying furnace, with muffles, crucibles, &c. are absolute-' ly necessary. See ASSAYING, Luton',