Blumenihal — Preparation of Selenic Acid. 95 



showing that the selenium had been oxidized almost com- 

 pletely to selenic acid, only a little selenious acid remaining. 



Next, the finely powdered metal (1 grm.) was fused with 

 sodium peroxide (5 grm.) in a nickel crucible, and after cool- 

 ing, the melt was partially neutralized with sulphuric acid, to 

 facilitate the analysis, and filtered. The filtrate and washings 

 were made up to 100 cm3 and 10 cm3 of this solution were anal- 

 yzed by the method of Gooch and Scoville.* Two analyses 

 showed the yield to be fairly quantitative, and suitable for the 

 analytical elimination of bromine. 



Preparation of the Reagent. — In utilizing the method on 

 a larger scale, about 105 grm. of powdered selenium and 

 500 grm. of sodium peroxide were thoroughly mixed and fused 

 in charges containing 10 grms. to 15 grms. of selenium, nickel 

 crucibles being employed. The reaction was rapid and a few 

 minutes' heating over a Bunsen burner sufficed to bring the 

 mass to liquid condition. After cooling, the crucible was 

 placed in a beaker of cold water, and covered with a watch- 

 glass to avoid loss by spattering. The melt dissolved with 

 great evolution of heat, and cold water was added from time 

 to time, to prevent boiling. Some finely divided material 

 remained floating in the strongly alkaline liquid. A slight 

 green color, probably clue to the solution of small amounts of 

 nickel, was also noticed. The solution could not be filtered 

 through paper, and a platinum cone, lined with asbestos, was 

 utilized, although the process was exceedingly laborious. The 

 opaque filtrate consisted chiefly of sodium selenate and sodium 

 hydroxide, with some sodium carbonate due to contact with 

 the air. 



In order to purify the selenate from sodium hydroxide, the 

 attempt was first made to remove the latter by shaking the 

 solution with alcohol. This procedure was found to have 

 several disadvantages. The amount of time involved, the 

 inconvenience of handling large quantities of strongly alkaline 

 solution, and the not inconsiderable amount of carbonate 

 formed, all militate against the process. But the greatest disad- 

 vantage lies in the fact that the dissolved carbonate and sele- 

 nate of the lower aqueous layer are very difficultly crystallized. 

 The successful method of purification ultimately developed 

 consisted in evaporating the alkaline liquid to pasty condition 

 over a free flame and removing as much caustic alkali as possi- 

 ble by continued extraction with alcohol which had been dis- 

 tilled from lime (97-99 per cent pure). The extraction was 

 hastened by warming on the steam bath, but in this latter 

 treatment, red, amorphous selenium was formed by reduction 

 of the solution. Six or eight extractions sufficed to remove 

 most of the hydroxide. 



* Gooch and Scoville, this Journal (3), 1, 402. 



