262 Bcrzelkis on<t new Mineral Body, [Oct. 



The solutions of the salts of barytes, stiontian, magnesia, 

 alumina, and the otjher earths, yield with the seleniuret of potash 

 insoluble, flesh-coloured compounds, from which the acids 

 separate selenium. Barytes and stiontian retain the selenium at 

 a red heat ; but it may be separated from the others by distil- 

 lation. 



If a metalline salt be precipitated by seleniuret of potash, the 

 selenium and the oxide precipitate together. This would take 

 place even if no affinity existed between the two bodies ; but as 

 selenium has a decided affinity for the strong saline bases, we 

 may conclude that it has an affinity likewise for the weak bases; 

 and that consequently these precipitates are real metalline sele- 

 niurets. I have not particularly studied this class of combina- 

 tions. I have produced some of them, and remained satisfied 

 "with the knowledge of their existence. 



Sulphur possesses the same property in common with sele- 

 nium ; but the metalline sulphurets have not been examined. I 

 have shown in the Elements of Chemistry, published in Swedish, 

 vol. ii. p. 113 — 213, that the protoxides of iron and cerium may 

 be combined with sulphur even in the dry way. 



Selenium may likewise be combined with melted wax and 

 with the fat oils, but not with the volatile oils. A solution of 

 selenium in olive oil appears orange and clear when seen by 

 transmitted light ; but pale-red, and muddy, by reflected light. 

 At the ordinary temperature of the atmosphere, it assumes the 

 consistence of an unguent, and loses the colour at the instant of 

 its congealing. The colour returns when we melt it. This 

 compound has no peculiar smell. It would appear that the 

 selenium merely dissolves in the oil without occasioning any 

 decomposition of it, as is done by sulphur. 



9. Combinations of Selenic Acid with the Bases. 



Selenic acid has a considerable degree of strength. It unite* 

 with oxide of silver when dropped into the nitrate of that metal; 

 and of the oxide of lead when dropped into the combination of 

 this oxide with muriatic or nitric acid. In consequence of its- 

 less volatility, it often displaces the nitric and muriatic acids by 

 distillation, and seizes on the bases with which they were united ; 

 but in its turn, it is expelled by the more fixed acids, as the 

 sulphuric, phosphoric, arsenic, and boracic. It seems to be 

 nearly on a footing with arsenic acid, or perhaps its affinity is 

 somewhat weaker. With the alkalies, it does not form neutral 

 salts. This is the case likewise with the phosphoric, arsenic, and 

 boracic acids. The compounds approaching nearest to neutra- 

 lity, and which, therefore, we call neutral, act on vegetable 

 colours like the bases and have an alkaline taste. All the neutral 

 seleniates formed with other bases are either insoluble or very 

 little soluble in water. In the neutral seleniates, the acid con- 



