472 
weights of the substances they represent. The numbers in 
column (3) are the same as those in (2), with the exception 
that the quotients for the lead and iron are added together. 
In (4) we have other numbers in the same ratio as the 
preceding. A mere inspection of the latter is sufficient 
to show that the empirical formula of the mineral is 
S, Pb, Sb; and such being the case, there can be no doubt 
that the rational formula is 
6 (S, Pb) + S83, Sb, 
or that it consists of six atoms of sulphuret of lead associated 
with one atom of tersulphuret of antimony, a little of the 
former metai being replaced by an equivalent quantity of 
iron. 
The above are the particulars of the analysis which ap- 
peared on the whole to have been most successfully per- 
formed ; the analysis, however, was repeated three times, 
and the results in each instance conducted to the formula 
just given. In the first trials, in consequence of strongly 
heating the ball traversed by the chlorine from the very 
commencement of the experiment, some of the chloride of lead 
was volatilized, and Dr. Apjohn was led to conclude the con- 
stitution of the mineral to be materially different from what it 
afterwards proved to be. The ball should not be heated 
until the spontaneous action of the chlorine on the ore has 
ceased. 
Kilbrickenite, as Dr. Apjohn proposed to call this mineral, 
is obviously what Berzelius denominates a sulphur salt, i. e., 
a combination of an electro-negative with an electro-positive 
sulphuret. But there are several other ores known to mine- 
ralogists composed of the same proximate constituents, or 
including sulphuret of lead in association with the sulphuret 
of antimony. The subjoined list comprehends those which 
have been analysed and described. 
