ON SILVER. STS*, 



the met?il, or even dissolve in it, so as not perceptibly to- 

 afl'ect its ductility, since it can be flattened out withoitt 

 shewing any defect in the plates. 



I repeated my assays, but with pure silver also ob- 

 tained from the muriat, and the surcharge disappeared. 

 This observation made me determine to dissolve the cor-, 

 nets, as often I should find reason to suspect aa extra-^ 

 ordinary surcharge. 



On the Nitrat of Silver. 



The acid that rises from a solution when evaporating it Silver carried 

 carries otf some silver, however gentle the ebullition may ®^.^" ^^^^^JJ". 

 be. The muriatic acid makes this known instantly, tion. 

 This result, which I have had opportunities of proving 

 several times', cannot fail to diminish a little the confi- 

 dence we might be inclined to place in assays of ores by 

 means of nitric acid ; and we know it is indispensable to 

 boil it long enough to resolve the last portions of sulphu- 

 ret of silver. 



The nitrat of silver does not appear to contain water Nitrat contains 

 of crystallization any more than nitre. It may be kept no water of 

 in fusion in a retort for a considerable time, without ^^^^ * ^ * ^^'^' 

 iosingmorethan a hundredth of its weight. On cooling 

 it fixes in a crystalline mass of a greyish hue, called lapis 

 infernalis. This nitrat, heated till it is completely de- 

 composed, leaves 64 hundredths of pure silver; from 

 which we may infer, that a hundred parts of silver will 

 produce 140 of nitrat [156*25]. 



A hundred parts of silver take 9| or 9| of oxigen to State of oxide 

 serve as a base to the nitrat, according to a trial I for- ^^ ' ^ nitrat. 

 merly made, though it would not be amiss to examine 

 the fact again. 



This nitrat then would consist of Coinpositlon 



Oxide of silver 69 or 70 Iilv° r'^' ""^ 



Nitric acid 31 30 



^ Oil assailing Ores of Silver. 



Many authors recommend, to precipitate the solution silver ores best 

 with copper; but this must be carefully avoided, for assayed m the 

 whatever care be taken, a little silver will always remain ^^ '^^^' 

 m the liquor, as the muriatic acid will shew. An ore that 

 Eec 2 yields 



