ORES. 



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 1 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 be 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 receiver. 



" 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 rendered insoluble 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 wiJl 

 take up the antimony, and leave the sul- 

 phur, if any. On dilution with water the 

 oxide of antimony is precipitated, and 

 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 



VOL. V. 



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. See 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, LABORA- 

 TORY, &c. 



The reduction of an ore requires fre- 

 quently previous roasting, to expel the 

 sulphur and other volatile ingredients ; 

 or this may be effected by mixing the 

 powdered ore with nitre, and projecting 

 the mixture into a crucible. The sul- 

 phate of potash, thus formed, may be 

 washed off, and the oxide must be re- 

 served for subsequent experiments. As 

 many of the metals retain their oxygen 

 so forcibly, that the application of heat 

 is incapable of expelling it, the addition 

 of inflammable matter becomes expe- 

 dient. And, to enable the reduced par- 

 ticles of metal to agglutinate and form a 

 collected mass, instead of scattered grains, 

 which would otherwise happen, some fu- 

 sible ingredient must be added, through 

 which, when in fusion, the reduced me- 

 tal may descend, and be collected at the 

 bottom of the crucible. Substances that 

 answer both these purposes are called 

 fluxes. The alkaline and earthy part of 

 fluxes serve also another end, viz. that 

 of combining with any acid which may 

 be attached to a metal, and which would 

 prevent its reduction, if not separated. 

 The ores of different metals, and differ- 

 ent ores of the same metal, require dif- 

 ferent fluxes. See FLUX. The ore, after 

 being roasted, if necessary, is to be well 

 mixed with three or four times its weight 

 of the flux, and put into a crucible, with 

 a little powdered charcoal over the sur- 

 face. A cover must be luted on, and the 

 crucible exposed to the necessary heat in 

 a wind-furnace. Ores of iron, as being 

 difficultly reduced, require a very intense 

 fire. Those of silver and lead are me- 

 tallized by a lower heat. The metal is 

 found at the bottom of the crucible, in 

 the form of a round button. The volatile 

 metals, as mercury, zinc, arsenic, tellu- 

 rium, and osmium, it is obvious, ought 



I 



