272 MAdNETICAL PYRITES. . 



pyrites, it may be proper to ftate fome comparative analyfes 

 which I have made of feveral of the common pyrites ; and, 

 as the method employed was precifely the fame as that which 

 has been defcribed, all that feems to be requiiite, is to give an 

 account of the remits. 



In each analyfis, the whole of the fulphur was converted 

 into fulphuric acid, which was precipitated by barytes ; and, 

 in the feleclion of the fpecimens, great attention was paid to 

 take the internal parts of the fragments, and not to make ufe 

 of any which exhibited an appearance of dec'ompofition, or 

 of extraneous fubftances. 



The iron was, as before, reduced to the ftate of black ox- 

 ide ; and the addition of weight in each feparate analyfis, 

 correfponded, within a few fractional parts, with the propor- 

 tion of oxigen requifite to form into black oxide a given quan- 

 tity of metallic iron, equal to that which in each pyrites was 

 afcertained to be the real proportion, by deducting the quan- 

 tity of fulphur from the total quantity of each pyrites. 



The iron, therefore, in thefe is completely metallic, and as 

 fuch is ftated in the following refults : 



The component No. 1. Pyrites in the form of dodecaedrons J j U P 1U jL'oe 

 partsofthecom- with pentagonal faces. 



mon pyrites 

 were, at a medi 

 urn, 9 fulphur 



and 8 iron, with j Sulphur 



l!on g . reac varia " No - 2 - p y rites in the form of flriated cubes - 



Specific gravity 4830. 





No. 3. Pyrites in the form of fmooth poliflied "| Sulphur 

 cubes, found in the lapis ollaris which I Iron 

 accompanies the magnetical pyrites. 

 Specific gravity 4831. J 



Sulphur 

 No. 4. Radiated pyrites. - (^ Iron 



Specific gravity 4698 



Sulphur 

 No. 5. A fmaller variety of radiated pyrites. I Iron 

 Specific gravity 477 



100. 



■ 52.50 



47.50 



100. 



• 52.70 



47. 30 



100. 



■ 5360 



46.40 



100. 



• 54.34 



45.66 



100. 



Confidering the difference in the figure, luftre, and colour 

 of thefe pyrites, I expected to have found a much greater 



difference 



i 



