76 °N ORPIMENT AND REALGAR, 



prove the ab- to me> t h e experiments adduced by this learned chemist are 



sence or oxi- , . r 



gen. not altogether sufficient to prove the nonexistence of o.vi- 



gcn in orpiment : for we may account for the result, whe- 

 ther we admit the existence of sulphuretted hidrogeu in 

 this compound, or that of an oxide less oxided than the 

 white oxide of arsenic. Mr. Proust has said nothing of real- 

 gar. 

 Bothsulphu- Both orpiment and realgar, if reduced to powder, and 



rets of arsenic • . ■■ » • *■'•*'% ,, i 



decomposed on P ro jected on burning coals, melt, swell up,, and emit sul- 

 the open fire, phurous acid : but all these phenomena are more obvious 

 and sublimed with realgar. Heated in close vessels the fusion and tume- 

 * faction are the same, and they are sublimed without chang- 

 ing their nature, consequently without giving out any sul- 

 phurous acid. 

 Realgar con- Sulphur fused with realgar converts it into orpiment; 

 g^k " while arsenic fused with orpiment converts it into realgar. 



Acids that at- The sulphuric, nitric, nitrous, and oxigenized muriatic 

 tack them. acid, are, as is well known, the only ones that attack orpi^ 



ment and realgar. 

 Sulphuric. Sulphuric acid acts perceptibly with greater power on or- 



piment than on realgar. In both cases sulphurous acid 

 is formed, and likewise arsenious acid ; but more sulphu- 

 rous acid, and less arsenious, are produced with the orpi- 

 ment. 

 ftitrlc, Nitric acid is decomposed by both these substances, even 



without the assistance of heat : and orpiment affords with it 

 more sulphur, and less arsenious acid, than realgar. 

 Oxigenized With oxigenized muriatic acid, and with the nitro-muri- 



nitro-muriatic a *' c ' tne same results are obtained as with the nitric. 

 Alkalis. The alkalis, particularly potash and soda, easily dissolve 



both, even cold. Hidroguretted sulphnret. of potash and 

 arsenite of potash are formed : since on pouring lime-water 

 into the solution a pretty copious white precipitate is obtain- 

 ed, which, treated with carbonate of potash, affords a liquor, 

 that yields, on adding a sufficient quantity of muriatic acid, 

 and evaporating to a proper point, a great deal of arsenious 

 acid. 



Orpiment con- ^11 these experiments show, that more sulphur is contam- 

 fcains most sul- . . . . . , , ,. , . , , 



phur, and nei- ed ,n orpiment than in realgar, and some ot them lead us to 



ther probably suspect, that no oxigeii is present in either. The following 

 ">J °* wUl 



