of Mineral Substances. 31 



with sulphuric acid and precipitated by zinc, gave 82 grains 

 of copper. 



B. 

 The above processes afforded no indications of antimony, 

 which, if present, probably escaped with the arsenic : 100 grains 

 of the ore, therefore, were roasted without the addition of 

 charcoal, and then digested in muriatic acid and dissolved by 

 the aid of nitric acid, added drop by drop. The filtered solu- 

 tion, which was of a green colour, was concentrated by evapo- 

 ration, supersaturated with potassa, boiled, diluted, and filtered. 

 The filtered alcaline liquor after having been neutralized with 

 sulphuric acid, and mixed with carbonate of potassa, was 

 scarcely rendered perceptibly turbid, 



C. 



To endeavour to ascertain the relative proportion of sulphur 

 to that of arsenic, 200 grains of the pulverized ore, mixed with 

 half their weight of charcoal powder, were submitted to sub- 

 limation. A few drops of moisture and some fcetid gas was 

 evolved, and the sublimate in the neck of the retort was opaque, 

 reddish brown, and of a metallic lustre ; but that in the dome of 

 the retort consisted of pure arsenic. The sublimate weighed 

 35 grains : it was pulverized and digested in weak solution of 

 potassa in a gentle heat; the liquid acquired a brown colour, 

 and left undissolved 23 grains of metallic arsenic in the form of 

 a heavy black powder; it afterwards deposited 1 grain more of 

 arsenic, and the solution became colourless ; the addition of 

 acids separated the sulphur in the form of egg-yellow flocks. 

 The colour of the sulphur, and the colouriess appearance of its 

 alcaline solution, indicated the existence of a portion of remain- 

 ing arsenic. 



Amidst these obstacles to accurate results*, I am induced to 

 estimate the proportion of sulphur at 10 per cent., and to assume 

 the following as the components of 100 parts of this ore :- 



• To the above Klaproth has added two otiier analyses of Falilerz, but as 

 they are nearly similar to that given in the text, and equally open to fallacy 

 as far as concerns the detennination of the weights of sulphur and 

 •rsenic, wc have omitted them. 



