1867.] 217 [Riotte. 



Composition. Two full analyses and several tests give for the spec- 

 imens sent : 



Found. Calculated. 



Ag=23.74. Ag=23.23. 



fe=1.82=feO=2.34. feO=2.41. 



S=4.7. S=4..59. 



Cu=12.78 Cu=2.32. CuO=13.08. CuO=13.28. 



SbO* SbO^=43.77 SbO*=46.03. Sb05=46.47. 



HO=7.9. 110=7.75. 



100.00. 



B. B. fuses easily, soon affording a globule of silver and copper, 

 and an intensely red colored slag. Upon very careful and strong 

 reduction on coal gives fumes of SbO^ In glass beads gives reac- 

 tions for copper, but even very small quantities make the beads 

 opaque. 



Plan of Anab/tils. The mineral w^as dissolved in concentrated fum- 

 ing NO^, and boiled till most of the surplus acid was gone. Then 

 diluted with water till no more SbO'' was precipitated, filtered and 

 the antimony determined as SbO^ SbO' by heating and burning 

 the filter with HgO ; from the solution the Ag was precipitated by 

 HCl. filtered ; then the SO^ was precipitated by BaCl. filtered. Then 

 the Cu, precipitated in the first case with SH and in the second (after 

 getting rid of the surplus BaCl. by SO^ and precipitating the fe with 

 ammonia) by precipitation with KO. 



Water was determined repeatedly by heating in a closed tube 

 (after drying at a temperature of 100°) and weighing until the 

 weight did not decrease. Thus from 6.5 per cent, to 8 per cent, were 

 found, agreeing in the average very well with the rest of the analysis. 

 A direct assay for water by means of a chlorcalcium tube as described 

 by Bunsen, made by Mr. C. A. Stetefeldt, gave nearly 10 per cent, 

 of water, but as all articles rec^uired could not be obtained here, he 

 thinks the difference can be accounted for. Sulphur was determined 

 thrice with limits from 4.5 per cent, to 4.77 per cent., the third being 

 the determination in the last analysis giving 4.7 per cent. 



If solved in Aqua Regia the insoluble precipitate is composed of 

 AgCl. and SbO'. 



The next question which arises from the analysis is, how are the 

 elements grouped in the mineral ? 



The silver is evidently combined with the sulphur. A direct ttst 

 made to determine this, jJroved it. The silver is easily reduced in a 

 glass tube if heated steam is passed over the mineral; at the same 



