JQ2 ON THE COMrOUNDS OF SULPHUR AND OXYGEN. 



Lac fulpburlu or I- ^^t is well Icnowti that fulphur, when firft obtained by 

 whitefulphur, is precipitation from any liquid, is always of a white colour, 

 fcrf Jel'"^ luU which gradually changes to greenifh yellow when the ful- 

 phur is the pure, phur is expofed to the open air. If this white powder, or lac 

 fulphuris, as It is called, be expofed to a low heat in a retort, 

 it foon acquires the colour of common fulphur ; and, at the 

 fame time, a quantity of water is depofited in the beak of the 

 retort. On the other hand, when a little water is dropt into 

 melted fulphur, the portion in contact with the water imme- 

 diately alTumes the white colour of lacfulpliuris. If common 

 fulphur be fublimed into a vefTel filled with the vapour of 

 water, we obtain lac fulphuris of the ufual whitcnefs, inftead 

 of the ufual flowers of fulphur. Thefe fa6ls prove that lac ful- 

 phuris Is ^ compound of fulphur and water. Hence we may 

 conclude that greenifli yellow is the natural colour of fulphur. 

 Whitenefs indicates the prefence of water. 

 Sulphur render. 2. It has been long known, that when a confiderablequan- 

 darJc.colou"ed ^'^y °^ fulphur is kept melted for fome time in an open veflel, 

 byfufion. it becomes vifcid, changes its colour to a dark violet, and ac- 



quires a kind of pitchy appearance. The nature of this change 

 has not hitherto been examined by chemifts. Fourcroy, in- 

 deed, affirms, that the fulphur, in this cafe, is in the (late of 

 an oxide. But the aflertion does not feem to have been the 

 refult of any pofitive experiment, 

 poes not fucceed j Jiave never been able to produce this change in the ap- 

 fgl, ' pearance of fulphur by heating it in a flat difli, where nothing 



impedes the volatilization, though I have kept it melted in a 

 glafs capfule on fand, heated to 250°, for ten hours toge- 

 ther. But the change takes place in a fliort time, when acon- 

 fiderable quantity of fulphur is kept melted In a crucible ; and 

 the greater the quantity employed, the fooner the change is 

 produced, and the more complete it is. 

 Thfs fuppofcd When fulphur, thus converted into a fuppofed oxide, is 

 let'colou°r-1s7oft "^wly prepared, its colour is a dark violet, with the metallic 

 if poured into luftre ; not very unlike newly-melted muriate of filver, when 

 rnfeVthTn fui? ''«^" ^X refleaed light. If it be thrown fuddenly, while in 

 phurj and tough, fufion, into water, it continues foft for a confiderable time j 

 and, as it hardens, the colour changes from purple to reddith 

 yellow. When broken, it exhibits a fibrous fracture, com- 

 pofed of fmall prifmatic cryflals. Its fpecific gravity was 

 2.325. It was very tough, refilling, with a good deal of ob- 

 4- ftinacy. 



