Chemical Science, 471 



Some of the sulphuret of selenium from Lukawitz, in Bohemia, 

 was dissolved in potash, and the solution converted into hyposul- 

 phite by exposure to the air at the temperature of 65° F. ; 0.1125 

 of the sulphuret experimented with were precipitated, and found 

 to be pure selenium. The solution being of a deeper red colour 

 than that of the common sulphuret, a piece of sulphur was put 

 into it, and the whole boiled for a moment ; a quarter of a grain of 

 selenium, perfectly free from sulphur, was precipitated. 



A solution of a neutral seleniate, or of one with excess of base, 

 is soon rendered turbid by having sulphuretted hydrogen passed 

 through it. At first pure selenium separates ; afterwards sulphuret 

 of selenium ; and, lastly, mere sulphur. The solution should be 

 considerably diluted ; when concentrated, the precipitate formed is 

 of a flame yellow colour, but soon becomes brownish-black, and 

 sulphur is deposited, sometimes crystallizing at the surface of the 

 deposite.— PAz7. Mag., N. S., ii. 390. 



13. On a new Compound of Selenium and Oxygen-^ Selenic Acid, 

 by MM. Mitscherlich and Nitzsch. — This acid contains half as 

 much more oxygen as that discovered by M. Berzelius, and with 

 potash forms a neutral salt, having the same form and optical pro-' 

 perties as sulphate of potash, containing no water when crystal- 

 lized, and producing insoluble precipitates with barytic salts. The 

 acid is isomorphous with the sulphuric, and may with propriety be 

 called selenic acid, that described by M. Berzelius being consi- 

 dered as the selenious acid. 



The new acid is easily prepared : for this purpose selenium, 

 selenious acid, a selenite or a metallic selenuret is to be fused with 

 nitre. Selenuret of lead, being the most abundant source, has 

 been used for this purpose, but being accompanied by sul- 

 phuret, the selenic acid is usually contaminated by sulphuric 

 acid. The selenuret of lead is to be freed from carbonates by 

 muriatic acid, and the residue mixed with its weight of nitrate of 

 soda, and thrown gradually into a red-hot crucible. Water then 

 dissolves out seleniate nitrate and nitrite of soda, no selenium 

 remaining in the residue The solution quickly boiled, deposits 

 anhydrous seleniate of soda, and this being separated, by cooling 

 crystals of nitrate of soda are formed; these being removed, ebulli- 

 tion again causes more seleniate to fall down, and proceeding in 

 this way an imperfect separation is effected. The seleniate, like 

 the sulphate of soda, is most soluble in water at 181°. To purify 

 the salt completely, the nitrite should be changed into nitrate by 

 nitric acid ; but then sulphate of soda would remain as an im- 

 purity formed from sulphuret in the ore, and no attempt to sepa- 

 rate this has as yet succeeded. 



But if the seleniate of soda be mixed with muriate of ammonia 

 and heated, selenium, nitrogen and water come over, no trace of 

 sulphur appearing. The selenium may, however, be dissolved in 

 excess of nitric acid, and the selenious acid produced tested by 



