Antilysis of the magnetlcal Pyrites. 143, 



• ??. 1"hat when to this residuum a quantity of sulphur \va3 

 added, and the whole was distilled iu a degree of licat not 

 too srreat, the 20 per cent, of sulphur, which had heen se- 

 parated by the first distillation, was by this again restored j 

 and the mass in the retort thus recovered nearly the original 

 colour, lustre, and chemical properties of the pyrites. 



4. That, by adding sul{)hur to iron filings, or tine iron 

 wire, heated to a low red in a retort, a compound is ob- 

 tained, in \\liich the proportion of sulphur amounts only 

 to about 20 or 30 parts ; but, if this compound is again, 

 treated with sulphur in a red heat, a Hulphuret is formed, 

 which is readily dissolved in acids, and plentifully affords 

 sulphuretted hydrogen gas. 



This is the real minimum of the sulphurets of iron, fixed 

 by the invariable law of proportions (according to Mr. 

 Proust) at 5f) or 60 of sulphur and 100 of iron, the former 

 being (as 1 have already observed) in the proportion of 

 37'5o per cent. 



5. and lastly. That when this sulphurct is again mixed 

 and distilled with sulphur, (due attention being paid to the 

 degree of heat,) ttie product is found to have assumed most 

 of the chemical and external properties of the natural com- 

 mon pvritcs, density alone being excepted. 



The application of the above observations to the principal 

 subject of the present paper is sufnciently obvious; for, 

 when it is considered that the maanetical pyrites is so dif- 

 ferent from the common pyrites iu colour, hardness, solu- 

 bility in sulphuric acid, and more especially in muriatic 

 acid, with the copious production of sulphuretted hydrogen 

 gas ; when, by analysis, it has I)een found to consist of 3^ 

 or 37 of sulphur, combined with about C3 of metallic iron; 

 and, when the artificial sulphuret of iron which has been 

 lately described is proveil to agree with the magnctical py- 

 rites in the nature and proportions of its component ingre- 

 dients, and in every one of the above-mentioned proper- 

 tics ; it is evident that the magnctical pyrites is identically 

 the same with this sulphurct, which hitherto has remained 

 undiscovered in nature, and has only been known as a pro- 

 duct of our laboratories. In order, however, more fully to 

 satisfy mvself, 1 made experiments on the artificial sulphu- 

 Tet, which 1 formed with sulphur and fine iron wire. 



This substance a-jreed, in all the properties which have 

 been noticed, with The iii;igrieiical pyrites ; and the precipi- 

 tates obtamed by adding prussiale of potash, and ammonia, 

 t« the muriatic and sulphuric solutions, were precisely si- 

 milar- 



