36 



Klaproth on the Chemical Analt/sis 



addition of water, and the precipitate collected, dried, and 

 heated, weighed 51.5 grains, which by collateral experiments 

 was found equivalent to 39.5 grains of antimony. 



So that 100 grains of the cupreous sulphuret of lead and 

 tintimony consist of 



100 



Analysis of the Sulphuret of Bismuth and Copper. 



This is a massive ore of a steel-gray colour, soft, and giving 



a black streak. 



A. 

 As a preliminary trial, 100 grains of the powdered ore were di- 

 gested in a moderate heat with nitric acid ; sulphur and fine sili- 

 ceous sand remained : the solution was filtered, somewhat diluted, 

 and tested by muriatic and sulphuric acids, neither of which 

 caused any turbidness, so that neither silver nor lead were 

 present. Water in larger quantity being added, a white oxide of 

 bismuth separated, and a plate of iron, immersed in the resi- 

 duary solution, threw down the copper. 



B. 



a. To determine the relative proportions of the ingredients of 

 this ore, two hundred grains were boiled in muriatic acid, and 

 nitric acid added, drop by drop, as long as it produced any 

 action. The insoluble portion was carefully collected, washed 

 and dried, and being duly heated the sulphur burned away 

 to the amount of 17.5 grains. The residue was again di- 

 gested in nitro-muriatic acid, and the portion which resisted its 

 action was properly washed, dried, and heated so as to burn off 

 the remaining sulphur, which amounted to 3 grains, leaving a 

 siliceous residue weighing 37 grains. 



b. The solution was evaporated till it acquired the appearance 



