VOL. LXXXVI.] PHILOSOPHICAL TRANSACTIONS. 43 



was the spear-head, and as it emitted more fume than the rest, I repeated the 

 process on this metal. The process of cupellation the 2d time, as before, caused 

 the appearance of the white fume, and afforded a residue of silver, as before, in 

 greater quantity than that of the test. The silver was determined in the most ac- 

 curate way to amount to the proportion of ] 5 grs. in a Troy pound of the spear- 

 head metal. There was no gold in this silver, for it dissolved totally in nitric acid. 

 § 5 . Experiments with nitric acid. — (a) A polished piece of each of the ancient 

 metals was just wetted with nitric acid. Fumes of nitrous acid arose, and the part 

 wetted became white and corroded; as is the case when the nitric acid has been 

 applied in this manner to the allay of copper by tin. 



(b) On 300 grs. of each of the above metals, in a small retort, were poured 

 1800gr. measures of nitric acid, purified by distillation from nitrate of silver, and 

 of the specific gravity of 1350. The hydro-pneumatic apparatus being affixed, 

 generally from 30 to 40 oz. measures of nitrous gaz came over in the cold, in the 

 course of 2 to 3 days. In this time the whole, or at least the greatest part of the 

 metal was oxydified and dissolved; there being a clear blue solution, with a copious 

 white sediment, and sometimes a part of the undissolved metal. By means of the 

 fire of a lamp, more gaz came over, which had been absorbed by the solution, and 

 which also was afforded by the dissolution of the remaining metal. The whole 

 quantity of nitrous gaz varied, with the same as well as with different metals, be- 

 tween 60 and 85 oz. measures; but either from my own inability to observe, or 

 from the circumstances on which this variety depended being unknown, I cannot 

 explain the reason of such differences in the result. 



(c) After the solution (b) had stood several days, the clear blue liquor was de- 

 canted, and filtrated, from the white sediment: and pure water was poured on the 

 filter repeatedly, till what passed through was colourless, and almost tasteless. The 

 filtrated liquid was boiled to evaporate all but about 6 oz.; and it deposited, on 

 standing, a small quantity of white sediment. 



The white sediment, from the solution (b,) being dried, amounted to the fol- 

 lowing different quantities, from 300 grs. of each of the different metals, namely, 



1. The sauce-pan, exclusive of a little dirty extraneous matter, . . ..65 grs. or 21 \ per cent. 



2. The spear-head, exclusive of a little dirty extraneous matter, .... 63 grs. or 21 per cent. 



3. The celt, N° 3 55 grs. or 18| per cent. 



4. The lituus, 54 grs. or 18 per. cent. , 



5. The scabbard, 48 grs. or \6 per cent. 



6. The celt, N° 1 42 grs. or 14 per cent. 



7. The celt, N° 2 42 grs. or 14 per cent. 



(d) The decanted and filtrated liquid (c,) being duly evaporated to crystallization, 

 was found to contain nothing but nitrate of copper, and sometimes a very minute 

 portion of white sediment; for it threw down nothing but prussiate of copper, on 

 adding prussiate of soda; nor was any silver deposited on immersing in it bright 

 copper wire; nor was any precipitation occasioned by adding muriatic acid, or 

 muriate of soda, to the concentrated blue solution. 



G2 



