*>W ORPIMENT AND REALGAR. 

 XIV. 



Remarks on Orpimcnt and Realgar: by Mr. Thenard*. 



?XZT mid "RPIMENT and realgar are two ores of arsenic sum-, 

 ciently abundant. The first is almost always in the form of 

 laminae of a pure yellow colour; and the second is as gene- 

 gaid to be the rally a red mass more or less brown. Bucquet asserted, that 

 of arsenic mo- these compounds were formed of oxide of arsenic, and sul- 

 difiedby heat; phur, in the same proportions, and ascribed their difference 

 of colour to the different degree of heat employed in pre- 

 thensulphurot- paring them. Bergman likewise admitted the oxide of ar- 

 fering m 'their semc » as well as sulphur, in both ; but he imagined they 

 proportions j differed in colour because they contained different propor- 

 tions. These opinions, supported by some experiments that 

 were capable of deceiving, prevented chemists for some time 

 fjjom forming a decided opinion: that of the Swedish che- 

 mist however prevailed, and since the creation of the new 

 theory, and the reform of chemical language, orpinient and 

 realgar are described in chemical treatises under the names 

 of yellow sulphuret of oxide of arsenic, aud red sulphuret- 

 and lastly ted oxide of arsenic. Nevertheless some have lately thought, 

 d£en?ox- f that these two substances differed less with respect to their 

 ides. proportions of sulphur, than those of their oxigen. 



Thus it has been successively supposed, 1st, that orpiment 

 and realgar were hornogeneal compounds containing burned 

 arsenic: 2dly, that they were oxides more or less sulphuret- 

 ted: and 3dly, that they were oxides more or less oxided, m 

 well as more or less sulphuretted. 

 AT-^montsfor The partisans of the first opinion ground it on the fact, 



the first opi- \\m\ by heating equal quantities of arser.ious acid and sul- 

 ttion. i i i • 



phur in a less or greater degree the product is sometimes or- 

 piment, at others realgar: therefore say they, if their colour 

 differ, it is owing to the heat, which occasions a different ar- 

 rangement of their particles. 



* Annates de Chimic, vol. L1X, p. 284, Sept. 1806. This paper was 

 read to the Phdomathic Society about a year ago. 



Those 



