Mineral Subjiance from New South Wales. jrj- 
Though no conclufion can be drawn from thefe experiments 
refpedting the comparative lojs of black-lead and the pure black 
matter of this mineral, on account of the heterogeneous parts 
intermixed with the latter, the colour of the refidua fee ms to 
afford a, fufficient difcrimination between them ; that of black* 
lead being dark rcddiffv brown, but the others purely and uni- 
formly white*. 
As this fubftance could not now be fuppofed to be either 
iron mica, or the common kind of black-lead, fufpicion fell 
upon ■. molybdasna. I had not, at that time, had an opportunity 
of procuring a fpeeimen of molybdama to compare it with 
but from the Angular and ftrongly-marked properties of the 
molybd^nic acid, difcovered by Scheele, it was judged, that 
a very fmail quantity of it, when di (engaged .from the fulphur 
with which it is naturally combined, would eaiily be diftin- 
guifhable. 
H jelm’s procefs for difengaging the fulphur, by repeatedly 
burning lihfeed oil upon the molybdaena in a crucible, and 
afterwards abflrafting fucceffive quantities of the fame oil from 
it in a retort, was tried on a portion of the Sydney-C.ove mi- 
neral, from which much of the white matter had been fepa- 
rated as above mentioned. The -black coal, remaining in the 
retort, became yellow by calcination, as that of molybdaena 
fhould do ; but in this yellow powder, no veftige of moiyb^ 
d^nic acid could be difcovered. 
Another quantity of the mineral, was fubmitted to ScheeleY 
own procefs, vm. repeated abftradlions of diluted nitrous acid ; 
but, inftead of becoming whiter every time, and at length 
white as chalk, which molybdaena fhould do, the blackneis of 
this matter continued unaltered to the lafb 
There, 
