1819.] extracted from P yritei- at Fahlun.- 103 



very easily with 100 parts of liquid sulphur, and the sulphur 

 acquires a dirty-yellow colour. A little sulphur being added to 

 the sulphuret of selenium (of which we shall speak immediately) 

 does not diminish its transparency ; but renders its colour paler. 

 A greater quantity of sulphur destroys the transparency. 



The only method of obtaining a sulphuret of selenium of a 

 determinate composition is to precipitate a solution of selenic 

 acid by sulphuretted hydrogen gas. The liquid becomes muddy, 

 and assumes a fine lemon colour ; but the sulphuret of selenium 

 is not easily separated from the liquid. If we add a few drops 

 of muriatic acid, it separates more easily ; and when we heat the 

 liquid, the precipitate coheres together, forming an elastic mass 

 of a deep orange colour. In this combination, 100 parts of 

 selenium are united to 60|. parts of sulphur. It contains an 

 atom of selenium and two atoms of sulphur. The sulphuret of 

 selenium thus obtained is very fusible. At the temperature of 

 boiling water it becomes soft, and the different pieces of it unite 

 into one. When heated a few degrees higher, it becomes fluid. 

 At a still higher temperature, it boils, and may be distilled over. 

 The portion thus distilled, when cold, is transparent, of a red 

 orange colour, and resembles melted orpiment. 



Sulphuret of selenium is attacked with difficulty by nitric 

 acid. Nitromuriatic acid dissolves it with much greater facility. 

 There remains a sulphur of an impure yellow, and sometimes 

 spotted-red, which retains a portion of the selenium with much 

 obstinacy. At last, the sulphur liquifies in the boiling liquid ; 

 and when it becomes yellow on cooling, it contains no more 

 selenium. 



Sulphuret of selenium is soluble in the fixed caustic alkalies, 

 as well as in the alkaline hydrosulphurets. The solution has a 

 very deep orange colour. The acids precipitate from it sulphuret 

 of selenium. 



If we heat this sulphuret in the air till the sulphur catches 

 fire, we perceive at first the odour of sulphurous acid, which by 

 degrees becomes mixed with that of horseradish, and at last this 

 odour prevails. If the air has not free access, selenium likewise 

 sublimes. If we heat together selenic acid and sulphuret of 

 selenium, the acid oxidizes the sulphur ; and I conceive that by 

 employing the requisite proportion of each, we may, by this 

 method, deprive selenium entirely of sulphur. 



Phosp/ntret of Selenium, — When we let a piece of selenium fall 

 on melted phosphorus, the selenium is speedily dissolved, and 

 the solution of it sinks in the melted phosphorus in reddish 

 striae, which gradually mix with the fused mass, so that selenium 

 may be mixed wilh phosphorus in all proportions, If we saturate 

 phosphorus with selenium, we obtain a very fusible compound, 

 which, when cold, has a dark-brown colour, much lustre, and a 

 vitreous fracture. 



If we digest phosphuret of selenium in water, a small portion 



