140 Analysis of the magnet lad Pyrites. 



afier the wax is burned^ combines with the superficial part 

 of the oxide, and converts a portion of it into the red or 

 peroxide ; so that the surface in the crucible appears browu 

 when compared with the interior. 



To this cause, therefore, I am inclined also to attribute 

 a small part of the increase observed in the weight of th« 

 iron obtained by the preceding analyses. 



§V. 



Before I make any observations on the nature of the sul- 

 phurct which has been proved to constitute the magnecical 

 pyrites, it may be proper to state some comparative analvses 

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

 as the method employed v/as precisely the same as that 

 which has been described, all that sec:»s to be requisite is 

 to give an account of the results. 



in each analysis the whole of the sulphur was converted 

 into sulphuric acid, which was precipitated bvbarytes; and, 

 in the selection of the specimens, great attention was paid 

 to take>the internal p<Trts of' the fragments, and not to make 

 use of any which exhibited an appearance of decomposition, 

 or of extraneous substances. 



The iron was, as before, reduced to the state of black 

 oxide J and the addition of weight in each separate analysis 

 corresponded, within a few fractional parts, with the pro- 

 portion of oxygen requisite to form into black oxide a given 

 quantity of metallic iron, equal to that which in each pyrites 

 was ascertained to be the real proportion, by deducting the 

 quantity of sulphur from the total quantity of each pyrites. 



The iron, therefore, in these is comjiletely metallic, and 

 as swch is stated in the following results. 

 No. 1. Pyrites in the form of dodccaedrons^ Sulphur 53-l.i 

 with pentagonal faces. - - I Iron 47'S5 



Specific gravity 4S30. C 



J 100- 



'Sulphur 52-30 

 No. 2. Pyrites in the form of striated cubes. I Iron 4 7'50 



X 



100' 



Ko. 3. Pvritcs m the form of smooth po-"i c i u c^. ^r. 



r 1 'i u V 1 • *'., 1 • II • Sulphur 52*70 



Iishcd cubes, round \\\ tne lapis ollaris K ' .- „„ 



, . , ' ,, ' ^- 1 I iron 47'30 



which accompanies the magnetical > 



pyrites. . " - - - joo- 



Speciuc gravity 4831. J 



No. 4. 



