AGUTCUI.TURAL MUSEUM 113 



tire mass decliictcd, gives the weight of (he second metal. 

 ^s this principle is of great use in investigating tlie eie- 

 ments of mixed metals, wc shall give an cxamp'e. Sup- 

 pose copper and silver mixed : dissolve the whole in 

 pure nitrous acid, properly diluted with wafer; apply to 

 the solution a mass of copper, the silver will be pracipita- 

 led. Pour off the solution, and wash the silver and un- 

 dissolved copper wi(h water; pour the Vv'ashirigs into the 

 soIutioHj weigh the mas? of copper left, and mark what 

 it has lost ; apply to thi solution a mass oi" iron, the 

 whole copper will be precipitated. Pour off the fluid, 

 and wasli the precipitate carefully, dry it and weigh it ; 

 deduct the weight lost from the mass of copper, wliat 

 remains is the weight of the copper in the mixture ; if 

 this weiglit, togetlury>ith that ot the silver, be the weigh.t 

 originally exposed to examination, there is no reason to 

 suspect any mixture of another metaL 



Jf the metals mixed are unknown, if we can find aii 

 acid which will dissolve them, ^\c may try to make a 

 jiiccipitation witli the nictal vi hich is lov.egt but one in 

 the ord:r of elective attractions, and so proceed to the 

 next above it, until we conie to the liighest ; and, by this 

 moans, we shall obtain all the metals in the mass. 



There are other iirincijrles on which i have founded va- 

 rious processes for assaying, but these are sufficient for 

 copper ores ; all the diffeicnt known species of which I 

 have actually assayed, arul therefore have ventured to of- 

 fer the consideration of this process to the society ; fii'st, 

 us only requiring an apparatus which can be bought at 

 any apolhecary^s or chymist's, and capable of being per- 

 formed by a person tqtally unacquainted v\ith chymistry, 

 so that any pi'oprietor of an estate, or his servant, may 

 determineif an ore be of copper, anditsvalue; secondly, 

 as aftbrding an assay master a more perfect manner of 

 determining the value of a copper ore; and lastlj-, as a 

 process by which the naturalist may investigate, not on- 

 ly the copper in an ore, but its various other contents. 



There is but one known species of copper ore ia 

 which the copper is not capable of being combined wiili 



