Intelh'ge?ice and Miscellaneous Articles. 643 



the same reagent, and the "washings" added to the original solu- 

 tion) was dissolved in acetic acid ; and a slip of pure lead being im- 

 mersed in the solution, the whole was covered up immediately and 

 suffered to stand for four hours. The slip of lead weighed 22*63 grs. 



The four hours having elapsed, the lead was taken from the solu- 

 tion, and, after separation of the precipitated bismuth, dried and 

 weighed. It weighed 19*21 grs.; loss, 3*42 grs. On the addition 

 of sulphuric acid, 5*03 grs. of sulphate of lead were obtained, which 

 are equal to 3*435 of lead ; and this amount corresponding so nearly 

 with the loss in the metallic precipitant, the whole of the lead pre- 

 sent in the mineral may be considered to have been converted into 

 PbO, SO^ by the first operation. 



The bismuth precipitate wad washed with cold distilled water 

 (which had been boiled), dissolved in nitric acid, and again thrown 

 down by carbonate of ammonia. The oxide of bismuth weighed 

 2"60 grs., equivalent to 2*33 grs. of bismuth. 



To tiie original solution (containing carbonate of ammonia) a few 

 drops of ammonia were added, and it was then gently evaporated 

 until the ammoniacal odour was entirely destroyed. Solution of 

 potash was then added, and the whole boiled. The black oxide of 

 copper, well-washed with hot water, ignited, and weighed in a 

 covered crucible, came to 1*31 grs., an amount equal to 1*05 of 

 copper. 



Finally, chloride of barium was added to the potash solution, 

 which produced a precipitate of sulphate of baryta weighing 5*72 

 grs., an amount corresponding to 0*79 of sulphur. The whole of 

 the sulphur present in the mineral was therefore 



1*57 grs. (0*52 + 026 + 0*79). 



The following table exhibits the above analysis and its atomic de- 

 ductions :— - 



Per cent. Atomic relations. 



Sulphur 1-57 18*78 0*0935 3 or 18 



Bismuth 2*33 27*93 0*0315 1 or 6 



Lead 3*36 40*10 0*0309 lor 6 



Copper 1*05 12*53 0-0317 1 or 6 



8*31 99*34 

 3Cu2 S, Bi^ S9 + 2(3PbS, Bi"- S^. 



This formula is identical with that of the bournonite (from the 

 analyses of H. Rose, Smithson, &c.), substituting only Bi^ S' for 

 Sb^ S^ as below : — 



Bournonite = 3Cu2 S, Sb^ S^ + 2(3PbS, Sb^ S^)- 



in each ore, the electro-negative atoms in the basic compounds 

 are, to the electro-negative atoms in the acid compounds, as 1 to 1, 

 as expressed in the accompanying general formula : — 



„ / Cu2 s \ , / Sb2 sn 



As the bournonite crystallizes also in the same system as the 

 needle ore, and indeed affects probably the same primary form within 

 close measurements, the isomorphous relationship of these minerals 

 is sufficiently apparent. 



