ON THE NATIVE SULPHVRETS OF IRON. 269 



VI. 



On the Native md Artificial Sulphurets of Iron, ^Professor 

 Proust*., 



IN a former memoir f I remarked, that the reafon why the why native ful- 



acids which eafily diflolve the artificial fulphuret, do not exer- phurets of iron 



. r ., r J . . /• i , m • arenotfoluble in 



cile the lame power on the native lulphuret, coniiits in an ex- ac ;d s y^ t t ear _ 



cefs of fulphur in the latter, which art has not yet fucceeded tificial. 

 in combining with iron. Hitherto in fact, I have not pre- 

 fumed that our imperfect means could approach fufficiently 

 near thofe of nature for us to hope to imitate the formation of 

 pyrites. Accident, however, has lately removed this diffi- 

 culty. 



I heated, without any particular attention to the quantities, iron pyrites 

 a mixture of about ten ounces of fulphur and of filings, in or- forn » ed b y art « 

 der to fupply my laboratory ; and judging by the colour that 

 the quantity of fulphur was infufficient, I thought proper to 

 add a new dofe. In confequence of this, the crucible was 

 made nearly red hot ; but not to fulion, becaufe it is more 

 convenient for ufe to obtain it in the ftate of powder. When 

 1 afterwards tried to diflolve it in an acid properly diluted, I 

 was fomewhat furprized to find that it did not afford fulphu- 

 rated hidrogen. It was to no purpofe that I altered the 

 flrength of my acid, for I obtained no gas. This unexpected 

 refult fliewed the poffibility of forming pyrites by art. 



Since pyrites becomes foluble as we have feen, only by de- Roafted pyrites 



priving it of the fulphur which exceeds its point of faturation, ? eft ° red . b y 8 iv r 

 b r r ' ing it the rebui- 



lt appeared to me, that I mould firli endeavour to reltore all f ltt dofe of ful- 



its qualities by producing its firfl flate from a fimilar excefs of P nu r» 

 fulphur ; and this in facl fucceeded. 



I mixed an indeterminate quantity of fulphur with four Experuneats. 

 hundred grains of the pyrites of Soria, deprived of its excefs 

 by diflillation, and I heated the mixture in a retort befide an- 

 other, which alfo contained four hundred grains of pyrites in 

 the crude flate. My object in this laft arrangement was to 

 obtain a kind of thermometer, to prevent my giving too great 

 a degree of heat to the firft retort ; that is to fay, not to ex- 



* Journal de Phyfique, Pluviofe X year. 

 f Philok Journal, I. 109, 



£>©fe 



