OF THE ATOMIC WEIGHT OF ALUMINUM. 
1.007 
scale, then sublimed from iron turnings, and re-sublimed from aluminum filings. It 
sometimes still contained traces of iron. Each specimen to be used was sublimed for 
the last time from aluminum, in a stream of dry hydrogen, into a small glass tube, 
which was sealed at both ends before the lamp, and reserved for one of the analytical 
experiments. Of these there were seven. In each the weight of the sealed tube and 
its contents was taken, a drawn out end opened, and the weight quickly verified after 
equilibrium of pressure with the outside air had been thus established; the tube was 
introduced into water, and after solution of its contents the weight of the empty tube 
was determined. It does not appear from the published paper how the risk of me¬ 
chanical loss from violent action of the chloride on the water was guarded against; 
from my own experiments with the bromide this appears to be a point requiring careful 
attention. Nor is it stated how the quantity of silver used was determined, whether 
by weighing the chloride of silver formed, by measuring the volume of a standard solu¬ 
tion of silver nitrate, or by weighing off a little less metallic silver than would be required, 
converting this into nitrate, adding it to the aluminum chloride solution, and com¬ 
pleting the precipitation with a measured quantity of dilute standard solution of silver 
nitrate. Nor is it mentioned how, if at all, the error due to slight solubility of silver 
chloride in the liquid from which it was precipitated is obviated—a point not ignored 
by Dumas, as appears from another part of the same paper,* and afterwards very 
carefully examined by Stas. 
The results of the seven experiments were as follows, the atomic weight or equiva¬ 
lent being calculated for the formula A.LC1 3 , and on the supposition that Ag=108, 
and Cl=35"5 :— 
I. 
Atomic weight. 
-D8786 of AI 0 CI 3 required 4"543 of Ag =13-74 
= 13-85 (should be 13"86) 
= 13-73 
= 13-68 
= 13-77 
= 13-68 
= 13-76 
II.- 
—3-02 It 
55 
55 
7-292 
III.- 
-2-399 
55 
55 
5-802 
IV.- 
-1-922 
55 
55 
4*6525 
V. 
—1-697 
55 
55 
4-1015 
VI¬ 
-4-3165 
55 
55 
10-448 
VID 
—6-728 
55 
55 
16-265 
Mean . 
Should be 
13-744 
13-746 or 27M92 for A1C1 3 
Recalculating this table for the formula A1C1 3 , and using the atomic weights of 
Stas for silver (107-66) and chlorine (35 "37), the figures of the last column become— 
* Page 135. 
f Contained traces of iron. 
