586 PROCEEDINGS OF THE AMERICAN ACADEMY. 



in a vacuum. The product, which contained a slight excess of bro- 

 mine, was fractionally distilled in a vacuum, and, as soon as the 

 excess of bromine had been eliminated, various fractions were col- 

 lected and analyzed for bromine in the usual way, after decomposition 

 with water and oxidation of the phosphorous acid produced. 



Purification of Materials. 



Water. — All the water used in this research was prepared from 

 the laboratory supply of distilled water by further distillation, first 

 from an alkaline permanganate solution, and then a second time, 

 after the addition of a trace of sulphuric acid, through a block tin 

 condenser. No rubber or cork was used in the connection between 

 the condenser tube and the Jena glass still. 



Ammonia. — The best commercial ammonia was distilled into the 

 purest water. 



Nitric Acid. — C. P. concentrated acid was distilled through a 

 platinum condenser, with rejection of the first two thirds of the dis- 

 tillate. It was always carefully tested in a nephelometer for traces 

 of halogens. 



Bromine.^ — This substance was freed from all but a trace of 

 chlorine by distillation from solution in a concentrated solution of 

 potassium bromide. The product was next converted into potassium 

 bromide by addition to a solution of recrystallized potassium oxalate. 

 In order to remove iodine the solution of potassium bromide was 

 boiled for some time, with the occasional addition of small amounts of 

 the partially purified bromine which had been saved for this purpose. 

 Toward the end of the boiling several small portions of potassium 

 permanganate and sulphuric acid were added to remove last traces 

 of iodine. Next the solution was evaporated to dryness and the dry 

 salt was fused in a large platinum crucible to destroy organic matter. 

 From the fused potassium bromide bromine was prepared as needed 

 by solution in water and the addition of sufficient potassium per- 

 manganate and sulphuric acid to oxidize three fourths of the bromide. 

 In this process the bromine was distilled a second time from a bro- 

 mide, and since this bromide was already nearly pure, last traces of 

 chlorine must have been eliminated from the product. The bromine 

 was separated as far as possible from water, and was dried by re- 

 sublimed phosphorus pentoxide, from which it was distilled imme- 



2 For a discussion of methods for purifying bromine see Richards and 

 Wells, These Proceedings, 41, 440 (1906); Baxter, Ibid., 42, 204 (1906); Jour. 

 Amer. Chem. Soc, 28, 1325; Zeit. anorg. Chem., 50, 392. 



