ORES. 



ted out when ordered to the field. 3. The 

 Surveyor General, who has the inspection 

 of the" ordnance, stores, and provisions of 

 war in the custody of the store-keepers : 

 he allows all bills of debt, keeps a check 

 on labourers, 8cc. 4. The Treasurer, 

 through whose hands passes the money 

 of the whole office, as well for payment 

 of salaries as debentures ; as also a Clerk 

 of the Ordnance, and a Clerk of the De- 

 liveries, for which see the articles, CJ.ERK. 

 of the ordnance, &c. 



ORES, in mineralogy. An ore is a me- 

 tal in the state in which it exists in the 

 earth. It may be either native, that is 

 pure, and uncombined with any other 

 substance, or alloyed with another me- 

 tal ; or in a state of an oxide, or a sulphu- 

 ret, or a carburet, or of a metallic salt. 

 It is also mixed in most instances with 

 various earthy minerals. The ores of 

 metals may be analyzed in two modes, in 

 the humid and the dry way. The first is 

 effected with the aid of acids, and of 

 other liquid agents, and may often be ac- 

 complished by very simple means, and 

 without the aid of a bulky and expensive 

 apparatus. If sulphur be present, it im- 

 pedes the action of acids, and should be 

 separated by roasting the ore on a muffle, 

 or by projecting it mixed with twice its 

 weight of nitre into a red-hot crucible, 

 washing off the alkali afterwards with hot 

 water. No solvent will act upon all the 

 metals. Thus nitric acid does not act on 

 gold and platina ; and the nitro-muriatic 

 acid, which dissolves these metals, has 

 no solvent action on silver. Hence the 

 necessity of varying the solvent accord- 

 ing to the nature of the ore under exa- 

 mination. We shall give a few instances, 

 by which'the reader will understand the 

 theory, and may be enabled to verify the 

 facts by practice. 



For " ores of gold and platina," the ni- 

 tro-muriatic acid is the most proper sol- 

 vent. A given weight of the ore may be 

 digested with this acid, as long as it ex- 

 tracts any thing. The solution is to be 

 evaporated to dryness, in order to expel 

 the excess of acid, and dissolved in wa- 

 ter. The addition of a solution of tin and 

 muriatic acid will shew the presence of 

 gold by a purple precipitate ; and platina 

 will be indicated by a precipitate, on 

 adding a solution of muriate of ammonia. 

 When gold and platina are both contain- 

 ed in the same solution, they may be se- 

 parated from each other by the last men- 

 tioned solution, which throws down the 

 platina, but not the gold. In this way 



platina may be detached also from other 

 metals. 



For extracting" silver" from.its ores, 

 the nitric acid is the most proper solvent. 

 The silver may be precipitated from ni- 

 tric acid by muriate of soda. Every hun- 

 dred part of the precipitate contains se- 

 venty-five of silver. But, as lead may be 

 present in the solution, and this metal is 

 also precipitated by muriate of soda, it 

 may be proper to immerse in the solu- 

 tion a polished plate of copper. This 

 will precipitate the silver, if present, in 

 a metallic form. The muriate of silver 

 is also soluble in liquid ammonia, which 

 that of lead is not. 



"Copper ores" may be analyzed by 

 boiling them with five times their weight 

 of concentrated sulphuric acid, till a dry 

 mass is obtained, from which water will 

 extract the sulphate of copper. This 

 salt is to be decomposed by a polished 

 plate of iron, immersed in a dilute solu- 

 tion of it. The copper will be precipi- 

 tated in a metallic state, and may be 

 scraped off' and weighed. If silver be 

 suspected with copper, nitrous acid must 

 be employed as the solvent ; and a plate 

 of polished copper will detect the silver. 



" Iron ores" may be dissolved in dilute 

 muriatic acid, or, if the metal be too 

 highly oxydized to be dissolved by this 

 acid, they must be previously mixed with 

 one-eighth of their weight of powdered 

 charcoal, and calcined in a crucible for an 

 hour. The iron is thus rendered solu- 

 ble. The solution must then be diluted 

 with ten or twelve times its quantity of 

 water, previously well boiled, to expel 

 the air, and must be preserved in a well- 

 stopped glass bottle for six or eight days. 

 The phosphate of iron will within that 

 time be precipitated, if any be present, 

 and the liquor must be decanted off. The 

 solution may contain the oxides of iron, 

 manganese, and zinc. It may be preci- 

 pitated by carbonate of soda, which will 

 separate them all. The oxide of zinc 

 will be taken up by a solution of pure 

 ammonia ; distilled vinegar will take up 

 the manganese, and will leave the oxide 

 of iron. From the weight of this, after 

 ignition, during a quarter of an hour, 

 twenty-eight per cent, may be deduct- 

 ed. 



" 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 



