Sodium monoselenide

Sulphur and selenium unite when warmed with the metal 51 when sulphur is triturated with sodium, the reaction proceeds with explosive violence which can be moderated by dilution with common salt. Under boiling toluene, sulphur forms the trisulphide Na2S3. Selenium forms the monoselenide, Na2Se, when heated with sodium. Sodium is attacked by hydrogen sulphide at ordinary temp., and at the fusion point the metal bums in the gas. Gaseous ammonia reacts readily with sodium, and liquid ammonia forms blue soln.—the so-called alkali-ammoniums. 

Sodium selenides.—The monoselenide, Na2Se, is formed by the action of selenium on a solution of excess of sodium in liquid ammonia, and separates out.6 It can also be produced by the interaction of selenium and sodium hyposulphite, Na2S204.6 It melts above 875° C., and on exposure to air its solution in water acquires a reddish colour, and deposits selenium. In solution it is extensively hydrolyzed, and under these conditions may be regarded as a mixture of sodium hydrogen selenide, NaSeH, and sodium hydroxide. Four hydrates are known, with 4, 9, 10, and 16 molecules of water respectively.7 For the heat of formation of the anhydrous compound Fabre8 gives 59 7 Cal., and for the heat of solution at 14° C., 18-6 Cal. He has also investigated the heat of solution of the hydrates. 

Potassium selenides.—The monoselenide, K2Se, is formed by the action of selenium on excess of potassium dissolved in liquid ammonia with excess of selenium the tetraselenide, KjSe is produced.3 Each compound resembles the corresponding sodium derivative. With solutions of potassium carbonate, hydrogen selenide reacts forming a number of hydrates of the monoselenide. The heat of formation of the anhydrous mono-derivative is given as 79-4 Cal.4 The triselenide has been isolated,5 and Fabre has also described the primary selenide, KSeH. 

Na2S04[lll] SODIUM SULFATE (III) 1150 NdSe NEODYMIUM MONOSELENIDE 1193... 

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