Sketch of the Mine of Pasco. 43 



Consideriflg this augmentation as oxide of titanium, its composi- 

 tion for 100. would be 



Iron, 60. 



Oxygen, - - - - - - - 21.60 



Protoxide of titanium, - - - - 18.40 



100. 

 Analysis. — Five grains of the same mineral, reduced to an impal- 

 pable powder, were treated by sulphuric acid, concentrated and boil- 

 ing. The solution was evaporated to dryness, taken by water, and 

 fdtered, the residue, insoluble, weighed 0.1. This residue gave no 

 indications of the oxide of titanium before the blowpipe. To the fil- 

 tered solution, tartaric acid and ammonia were added by turns, un- 

 til the latter produced no precipitate. A small excess of hydro sul- 

 phate of ammonia was then added, and the hydro-sulphuret of iron 

 separated by filtration, tlie solution evaporated to dryness, and the 

 residue calcined, gave 0.95 of the protoxide of titanium. 



This mineral may be considered as having the following composi- 

 tion for 100. 



Iron, ____-_- 60. 



Oxide of titanium, - - - - - 19. 



Silex, _______ 2. 



Oxygen, ------- 19. 



This quantity of oxygen is not exact, the iron containing an indefi- 

 nite quantity of carbon. 



Art. V. — Sketch of the rich mine of Pasco ; hy M. de Rivebo, 

 received from the author in his Journal of JVatural Science, and 

 JYational and Foreign Industry, Jan. 1828, J^ol. I. JVo. 2. pub- 

 lished at Lima, and translated for this Journal by a Scholar of 

 the JYew Haven Gymnasium. 



Introductory notice of specimens of silver froin Peru and Chili. — Ed. 



Mr. Rivero's account of the mineral riches of Pasco has excited 

 the more interest in my mind, because some of those riches, and of 

 those of the contiguous country of Chili, have been recently deposit- 

 ed in my hands, by the kindness of Mr. Daniel W. Coit. This 

 gentleman, for many years a traveller and resident in various coun- 

 tries in Europe and both Americas ; and for the last six or seven 



