M. Weber on Selenium Compounds. 297 



The following seleniates were prepared by dissolving the car- 

 bonates or hydrates in selenic acid : — 



Seleniate of Soda, NaO, Se0 3 + 10 Aq — Large crystals resem- 

 bling Glauber's salt. 



Seleniate of Lime, CaO, SeO 3 + 2 Aq.— Needles like sulphate of 

 lime. 



Seleniate of Nickel, NiO, SeO 3 + 6 Aq. — Thesecrystals resemble 

 the corresponding sulphate, as has been shown by Mitscherlich. 

 They lose four equivs. of water at 100°. 



Seleniate of Nickel and Potassium, KO, NiO, 2Se0 3 + 6Aq. — 

 Obtained by the spontaneous evaporation of a solution of the 

 two salts. They lose four equivs. of water at 100°. The analo- 

 gous sulphate is not perceptibly altered at 100°. 



Seleniate of Cadmium, CdO, SeO 3 + 2 Aq.— These crystals differ 

 both in form and composition from those of the corresponding 

 sulphate. They lose 1 equiv. of water at 100°. 



Weber has described the formation of oxy chloride of selenium 

 and of the alum of selenic acid*. The former body is obtained 

 by distilling chloride of selenium, SeCl 2 , so that it comes in con- 

 tact with an equal volume of selenious acid. The two bodies 

 combine to form white vapours of oxy chloride of selenium, 

 which is redistilled over selenious acid. 



It is a yellowish liquid which fumes in moist air ; it has the 

 density 2*44, and boils at about 240°. It dissolves readily in 

 water, forming hydrochloric acid and selenious acid. Its compo- 

 sition may be expressed by the formula SeCl 2 4- SeO 2 , according 

 to which it is a compound of selenious acid and of chloride of 

 selenium. It may also be considered as being selenious acid 

 in which an atom of oxygen is replaced by an atom of chlorine. 

 Oxychloride of selenium is also formed by the action of a small 

 quantity of water on chloride of selenium. 



It was found impossible to prepare a compound corresponding 

 to Regnault/s chlorosulphuric acid. Chlorine is without action 

 on dry selenious acid. 



To prepare selenic acid, selenite of soda was fused with nitrate 

 of potass, the mixture treated with nitrate of lead, and the pre- 

 cipitate of seleniate of lead decomposed by sulphuretted hydro- 

 gen. The solution of selenic acid was concentrated, and a 

 quarter of it neutralized with carbonate of potass ; the remaining 

 three quarters were digested with pure hydrate of alumina. The 

 mixed liquids were left to spontaneous evaporation, and after the 

 expiration of twenty days, beautiful crystals were obtained. Their 

 composition was Al 2 O 3 , 3Se0 3 , KO, SeO 3 + 24 HO. The crystals 



* Poggendorff's Annalen, vol. cviii. p. 613. 

 Phil Mag. S. 4. Vol. 20. No. 133. Oct. 1860. X 



