518 SELENIUM. 



then present. Concentrated at a heat above 576, and deducting 

 the selenious acid present, it appeared to contain 15.75 water. 



(c.) Attracts water powerfully, and by combining with it, evolves 

 as much heat as sulphuric acid. 



(d.) Boiled with muriatic acid, selenious acid is deposited and 

 chlorine liberated, and the solution dissolves gold but not platinum ; 

 it resembles aqua regia, and probably contains it. 



It unites with alkaline bases and forms salts, which are with diffi- 

 culty decomposed by sulphuric acid, which it appears strongly to re- 

 semble. 



(jf.) Selenic acid dissolves iron and zinc, with disengagement of 

 hydrogen gas. 



3. ITS EQUIVALENT. It appears to contain 3 equivalents of oxy- 

 gen, 24-f-l of selenium, 40 = 64. 



CLASSIFICATION. Selenium resembles the metals in sp. gr., and 

 metallic lustre, and in most of its chemical properties, but it is a non- 

 conductor of heat and electricity. Berzelius ranked it with the met- 

 als, and it has a considerable resemblance to tellurium, but it is rather 

 more like sulphur, and on the whole seems to form a connecting link 

 between the combustibles and the metals. Its combination with hy- 

 drogen appears to be particularly noxious, and it is probable that it 

 often renders sulphuretted hydrogen more noxious, since there is reason 

 to believe that it is not unfrequently present i*that gas, as sulphur is 

 often contaminated by it. It is obtained by heating the seleniuret of 

 iron with muriatic acid, by an obvious theory. The gas is acid and 

 has been called hydro-selenic acid and seleniuretted hydrogen. It is 

 colorless, fetid, irritates and paralyses the membrane of the nose for 

 some hours, so that the sense of smell is destroyed ; it is dissolved by 

 water and stains the skin brown. It is decomposed by the air and 

 leaves selenium. With all the metallic solutions it forms seleniurets.* 



Selenium being as yet a substance very difficult to be obtained, we 

 must refer, for numerous additional particulars and for the history of 

 the seleniates,, to the elaborate mempir of Berzelius, in the ninth vol- 

 ume of the Annales de Chimie et de Physique. 



* Turner, 2d ed. p. 356. 



END OF VOL. 1. 



