380 PROCEEDINGS OP TUE AMERICAN ACADEMY. 



purified by many recrystallizations from hydrochloric acid and water. 

 The amnionic oxalate was crystallized twice in a platinum dish, the 

 crystals being thoroughly washed each time. The salt was wholly 

 free from chlorine. 



Ammonic Bromide was prepared in the usual fashion from ammonia 

 prepared in platinum and bromine purified according to Stas. The 

 reaction was naturally conducted in a flask of hard glass ; but the 

 crystallization was carried on as usual in platinum. A slight excess 

 of the pure white substance precipitated 3.97970 grams of argentic 

 bromide (fused, reduced to the vacuum standard) from a solution 

 containing 2.28G16 grams of pure silver. From this experiment 

 AgBr : Ag = 100 : 57.4455. Stas found 57.445, hence the purity of 

 the ammonic bromide is proved. 



A very simple and convenient platinum condenser was used for the 

 preparation work described above. The tube, almost a centimeter in 

 diameter and perhaps twenty-five centimeters in length, is bent, some- 

 what contracted near one end, and surrounded with a condenser jacket. 

 It is easy to draw out the neck of a round-bottomed flask to fit outside 

 of the conical end, and if the juncture is not absolutely tight a thin 

 film of condensed liquid soon makes it so. If the glass neck be pro- 

 longed somewhat above the point of juncture, evaporation from this 

 film is very slow. Of course pure filter paper may be used to tighten 

 the joint if water is to be distilled. The apparatus has the great 

 advantages of cheapness and transparency over the ordinary platinum 

 still. All the hydrochloric, hydrobromic, sulphuric, and nitric acids, 

 water, and alcohol used in the important stages of the work were 

 distilled with the help of this contrivance. 



Platinum vessels have been used wherever it was possible to use 

 them in the work detailed above, although the fact is not always 

 mentioned. They were cleaned in the usual fashion. 



Method of Analysis. 



As in the case of baric bromide,* the silver required to precipitate 

 all the bromine in strontic bromide was determined, as well as the 

 amount of argentic bromide formed by the precipitation. 



The chief problem which presented itself was the preparation of 

 pure dry neutral bromide of strontium for weighing. In preliminary 

 analyses the salt was ignited or fused in a platinum crucible, and 



* These Proceedings, XXVIII. 23. 



