44 J. P. Cooke—Atomic Weight of Antimony. 
We were for some time in doubt in what condition the sul- 
phide of antimony ought to be weighed, in order to obtain the 
most accurate results. Our final judgment was that the errors 
already referred to would best be balanced, while others would 
be avoided, by weighing the sulphide, after it had been dried, 
at from 180° to 200° , but before it was actually converted into 
the gray sulphide "This conversion takes place between 210° 
and 220°, varying to that extent in different cases. The change, 
as we infer, is attended with a sudden evolution of heat, and 
the action is quite violent. Small particles of the material are 
See projected from the vessel, and we sometimes noticed 
that the surface of the platinum nacelle became coated with the 
familiar sublimate of sulphide of antimony. If there is oxi- 
chloride in the precipitate, there may be an additional volatiliza- 
tion of chloride of antimony at this time; but the main loss, as 
we have constantly observed, ee place before the point of 
conversion is reac e therefore concluded that more 
trustworthy results could be deduedl from the wees of the 
red sulphide dried, as we have described, than from that of the 
gray ; and, as will ‘be seen, this judgment was fully confirmed 
by subsequent experiments on the haloid compounds. We 
have, however, in all but two instances weighed the sulphide 
in both con ditions, and we give the results of both yelptiaes : 
and on comparing these results in determinations eight to 
thirteen inclusive of the table on page 48, which were made 
under the nearly identical conditions we have above indicated, 
it will be seen that the differences are far smaller with the red 
sulphide than with the gray, which shows conclusively that 
additional causes of error must have affected the last weights, 
—a circumstance which sustains our judgment. 
n the first twelve determinations we did not estimate the 
amount of the carbonaceous residue, which is assumed to 
without the usual occlusion — een onde In this case, there 
was no evidence . sublimation nor loss during conversion, but 
a proportionally large carbonaceous residue, which was deducted 
from the ncaa of the sulphide; and the result of this deter- 
mination, as ‘will be seen, still further corroborates our conclu- 
sion. The same is true of the analyses of chloride of antimony 
made more recently, in which we dissolved crystallized chloride 
of antimony in a concentrated aqueous solution of tartaric acid, 
without using any excess of hydrochloric acid. In these cases 
, the drying of the precipitate, and the conversion from the 
red to the gray modification, were attended with no appearance 
