MR CONNELL ON SULPHURET OF CADMIUM. 621 



This large crystal was a somewhat imperfectly formed six-sided pyramid, 

 one of the faces of the pyramid being apparently obliterated by the extension of 

 the two contiguous ; the faces being transversely streaked, and with traces also 

 of a six-sided prism. It possessed a slightly reddish yellow colour, and consi- 

 derable transparency, except in one or two small points, which were dark coloured 

 and opaque. Its streak was orange-red as that of the others. When detached it 

 weighed 3.68 grains. Suspended in distilled water by a fine hair, it lost .76 of a 

 grain, giving its specific gravity as 4.842 at 60° F. ; which thus considerably ex- 

 ceeds the specific gravity of zinc-blende. I then detached from it the darker 

 and opaque particles, and substituted for them a small quantity of yellow and 

 transparent portions from another crystallized specimen, also given me by Lord 

 Greenock. 



3.71 grains thus selected were reduced to somewhat coarse powder, and 

 fuming nitric acid was poured on them, drop by drop, in a deep flask. The action 

 was violent, and attended by a copious evolution of red fumes, but not the least 

 smell of sulphuretted hydrogen was observed. An excess of nitric acid was 

 then added, and the whole digested till all the sulphur which had separated 

 was dissolved. Water was then added, and the sulphuric acid thrown down 

 by muriate of barytes. The sulphate of bar3rtes, after being well washed with 

 hot water, was dried and ignited, and weighed 6.07 grains, equivalent to .837 of 

 sulphur. 



The excess of barytes was then removed from the liquid, after concentration 

 by heat, by sulphuric acid. After again concentrating, carbonate of ammonia 

 was added in excess. The carbonate of cadmium was separated by filtration, 

 and well washed, dried, and ignited. The oxide of cadmium thus obtained had 

 an ochre-yellow colour, and weighed 3.28 grains, equivalent to 2.868 of cadmium. 

 A little of it dissolved in muriatic acid, was enthely taken up by excess of am- 

 monia. 



The filtered liquid was then evaporated by heat, but no precipitation had 

 taken place when all smeU of carbonate of ammonia had disappeared ; thereby 

 confirming the previous observations as to the absence of zinc. The evaporation 

 was carried to dr3Tiess, and the ammoniacal salt driven off by heat. A residue 

 of .04 remained, of a reddish- white colour, which, in so far as its small quantity 

 permitted examination, was found to be, in part at least, a subsulphate of iron, 

 insoluble in water, and scarce soluble even in acids till previously boiled with 

 potash ; but as the proportion of its constituents could not be determined on so 

 little material, the iron could not be computed in any other way than by stating 

 it as a trace in the mineral, its amount, on any view, being very small ; and if 

 more than such, this was not the stage of the analysis in which it ought to have 

 been obtained. 



