1022 
PROFESSOR J. W. MALLET ON A REVISION 
use, for some at least of the experiments, an excess of silver, filter off the silver 
bromide formed, and determine silver in the filtrate by Volhard’s method"' with a 
standard solution of sulpho-cyanate ; but this plan was abandoned as less simple, and 
probably requiring further investigation in regard to inherent sources of error and 
limits of accuracy. The completion of the reaction was therefore ascertained simply 
by very cautious addition of the standard silver solution until all trace of turbidity 
ceased, verifying the result by counter test with a drop of very dilute solution of 
potassium bromide. By letting the bottle stand for a little while after each addition 
of silver solution and shaking, and then tilting it to one side so as to bring the upper 
portion of the liquid above the line it had before occupied on the glass, letting the 
new drop fall gently in, an exceedingly slight cloud was easily seen. 
It should be added that the silver globules and the tubes of aluminum bromide, 
after final cleansing and drying, were handled only with forceps, so as to avoid any 
risk of traces of chlorides being taken up from the fingers, and due attention was 
given to the freedom of the laboratory atmosphere from hydrochloric acid or chlorine 
in other volatile forms. 
Direct results of second series of experiments. —The results of the experiments made 
in this way were— 
A.—Aluminum bromide from first portion of last distillate. 
6'0024 grms. of AlBr 3 required 7‘2793 grms. of Ag for precipitation 
8- 6492 „ „ 10-4897 
3- 1808 „ „ 3-8573 
B. —Aluminum bromide from second portion of last distillate. 
IV.— 6*9617 grms. of AlBr 3 required 8"4429 grms. of Ag for precipitation. 
V—11-2041 
VI.— 3-7621 
VII.— 5-2842 
VIII.— 9-7338 
C. —Aluminum bromide from third portion of last distillate. 
9- 3 515 grms. of AlBr 3 required 11 "3424 grms. of Ag for precipitation. 
4- 4426 „ „ 5-3877 „ „ 
5- 2750 „ „ 6-3975 
Third series of experiments. 
Preparation of pure metallic aluminum. —A further supply of pure aluminum 
bromide having been made as above described, it was used to prepare metallic 
aluminum by reduction with sodium. 
* Fresenjus’ ‘ Zeitsclirift fiir analyt. Cliemie,’ 18 ter Jalirg., 2 tcs u. 3 tes Heft., S. 271. 
IX.— 
X.— 
XI.— 
13-5897 
4-5624 
6-4085 
11-8047 
I.— 
II.— 
III.— 
