66 PROCEEDINGS OF THE AMERICAN ACADEMY 



No. WtofSbBrg. ^^tb^o'^Bi-^!'^ % of residue. 



1. 2.8342 0.0010 0.035 



2. 2.0220 0.0006 0.030 



3. 4.6730 0.0010 0.021 



As will be seen, this residue is less than one-tenth of that obtained 

 from the chloride, and is practically insignificant. Evidently, then, in 

 the determination of the atomic weight of antimony more accurate 

 results may be expected from the analysis of the bromide than from 

 the analysis of either the chloride or the iodide of this element. The 

 intermediate position of the bromide renders it, in a very remarkable 

 way, the most stable of the three compounds. It absorbs moisture far 

 less eagerly than the chloride, and it absorbs oxygen far less readily 

 than the iodide, and is thus in great measure protected against each of 

 these two sources of the same impurity. 



We come finally to the new analyses of antimonious chloride we 

 had undertaken. Fortunately, some of the old preparation that had 

 been distilled so often had been preserved. It had been boiled for a 

 long time since the last analyses were made, and kept in the same flask 

 used for determining its boiling point, which had stood meanwhile 

 tightly corked in a desiccator over sulphuric acid. The solid mass in 

 the flask was easily broken up without exposure to the air by simply 

 heating it to the melting point, and shaking it in the flask as soon as, 

 beginning to melt, the mass had separated from the glass. Near its 

 melting point, chloride of antimony becomes very friable, and is thus 

 easily reduced to coarse powder, whence probably the old alchemistic 

 name of butter of antimony. It is also worthy of notice that neither 

 the bromide nor the iodide acts in this way, as we found out in more 

 than one instance to our cost. 



Thus we were readily able to prepare our material for analysis, 

 and, by a thorough mixing of the mass, to insure that the several 

 samples taken had a uniform composition. In regard to the antimony 

 determination, no further details are necessary. It was conducted, as 

 described before, with every minute precaution which experience had 

 suggested ; and we give the full details, in order to show how completely 

 we had been able to overcome the difficulties which it at first presented, 

 and we feel confident that there is no process of wet analysis which is 

 capable of giving more accurate results than this. 



