Scientific NoticeA^Mineralogy* fSEFt, 



strongly ; becomes yellow by the action of sulphuric acid, and 

 red by sulphuretted hydrogen: hence it is similar to selenic 

 acid. 



Cold nitric acid acts on seleniuret of lead, and after some time 

 the mass assumes a cinnamon red colour^ in consequence of the 

 separation of selenium, if the acid be heated, the whole of the 

 ore is dissolved, the selenium first separating in the form of red 

 flakes, which soon lose their colour, turn brown, and gradually 

 disappear. If the quantity of ore be in excess, the selenium 

 collects in brown flakes on the surface of the solution, which 

 sometimes assumes the appearance of an oily film. 



The nitric acid solution has a pale reddish colour, derived from 

 a slight portion of cobalt ; but no other metal, besides lead and 

 cobalt, is contained in the ore ; neither is any trace of sulphur 

 detected by the action of nitrate of barytes. 



The analysis of this ore gave M. Stromeyer per cent. 



Lead 70-98 



Cobalt 0-83 



Selenium 28-11 



99-92 



6. Selenium in the Sulphur of the Lipari Isles. 



Amongst the volcanic productions of the Lipari Isles, a sal 

 ammoniac is found combined with sublimed sulphur in alternate 

 white and brownish orange layers, the colour of the latter of 

 which has generally been attributed to iron. On examination, 

 however, heither tincture of galls, prussiate of potash, nor 

 ammonia, gave any indication of that metal, but sulphuretted 

 hydrogen gave a precipitate of orpiment, owing to the presence 

 of some arsenious acid. 



When the sal ammoniac is dissolved in water, a brownish 

 yellow residuum is left, which fuses readily in a glass tube, and 

 affords an orange coloured sublimate. On hot coals it inflames, 

 and exhales at first a mixed odour of sulphur and arsenic, which 

 is succeeded by the peculiar offensive smell of selenium. By 

 digestion in nitric acid till the orange colour disappeared, a solu- 

 tion was obtained from which sulphate of potash threw down a 

 considerable quantity of a cinnabar coloured precipitate, possess- 

 ing all the characters of selenium ; and the solution afforded by 

 evaporation acicular crystals of selenic acid. 



This discovery by M. Stromeyer of selenium amongst the vol- 

 canic products of the Lipari Islands, renders it probable that the 

 peculiar orange tint of the sulphur found in those islands pro- 

 ceeds chiefly from selenium, and not, as hitherto supposed, from 

 arsenic combined with the sulphur. 



