42 J. P. Cooke—Atomic Weight of Antimony. 
from the circumstance that the antimonious sulphide as usually 
precipitated occludes a small amount of tartaric acid on the 
one hand and of oxichloride of antimony on the other. These 
occlusions tend to produce errors in opposite directions, for 
when, before weighing, the red antimonious sulphide is heated 
to the point of its conversion into the gray modification, the 
tartaric acid is charred, and the carbonaceous residue increases 
the apparent weight of the product; while on the other hand 
the oxichloride of antimony is decomposed at the same tem- 
perature and the antimonious chloride, which volatilizes, tends 
to diminish the weight of the product. In the earlier deter- 
minations these causes of error were balanced as nearly as 
possible by regulating the conditions of the precipitation; but 
it was subsequently found to be possible to entirely prevent the 
occlusion of antimonious oxichloride, and in all the later deter- 
minations allowance was made for the small amount of carbon- 
lowing determinations of the specific gravities of the different 
C., on 
the assumption that the coefficient of cubic expansion for anti- 
mony between 0° and 100° C. is for each degree 0:0000838, as 
bserved by Kopp. The letters here given will be used 
throughout the table to designate the various specimens. As 
might be supposed, the specimens were prepared at different 
times and at different stages of the investigation, but the results 
are united here for the convenience of comparison and of refer- 
ence. 
Spreciric Graviries oF Butrons or Pure Metatiic ANTIMONY. 
Observations of J. P. C., Jr. Observations of W. Dexter. 
A ie 1000 | DL. . 6°7087 
Be 70s |) 6 ee 6°7026 
» 6°6957 | ¢ . .6°6987 
D 6°7070 | d 6°7102 
Bec Se Oe ee 6°7047 
Rea, Re Aeien ee 6700S) SiS Se 6°7052 
Mean...... -. ....6°7022 | Mean 6°7050 
The processes used in preparing the several buttons just 
referred to, the method by which the metal was brought into 
solution in its lowest condition of quantivalence, and the man- 
ner in which the antimonious sulphide was precipitated, col- 
lected, dried and ene are all described at length in the 
original paper. The following table shows the results which 
were obtained. 
*Poggendorff’s Annalen, ¢, 564 (I. c.). 
