Anahjsis of the magnetical Pyrites, 2 1 5 



phurcts of iron may be regarded as bodies peculiarly sus- 

 ceptible of strong magnetical impregnation. 



Havincr thus, for the greater perspicuity, reduced the 

 principal" facts of this paper into a concise order, 1 shall 

 now make some general observations. 



It is undoubtedly not a little singular, that a substance 

 like the mao-neticalpv^tcs, which, although not common, 

 has been long known to mineralogists, should not hitherto 

 have been chemically examined, especially as mmeralogical 

 authors have mentioned the analvsis ot it as a desidcratuni. 

 The result of this which I have attempted, proves that it is 

 really deserving of notice; for thus we have ascertanied, 

 that the sulphuret of iron hitherto known only as an arti- 

 ficial product, is also formed by nature, and that the com- 

 position of this last agrees with those proportions o^ the 

 artificial sulphuret which have been stated by Mr. I roust. 



But from this sulphuret or raao;netical pyrites I have 

 not, bv analysis, as yet been able to discover any regular 

 or immediate aradations into the common pyrites ; tor the 

 least proportion of sulphur in these amounted to 32-15, and 

 the greatest proportion to 54-34 ; so that, between the mag- 

 netical and the common pyrites, the difference is considera- 

 ble, in the proportions of 'their component substances, as 

 well as in their physical and chemical properties; whilst 

 the difference which I have hitherto been able to detect in 

 the proportions of some of the common pyrites, (very dis- 

 similar in figure, lustre, colour, and hardness,) has only 

 amounted to 2-19. 



Mr Proust, in a o-encral way, considers comnion pyrites 

 to differ from the Hrst sulphuret, or that composed of Co 

 parts of sulphur and 100 of iron, (= 37-50 per cent.) by 

 containincr a further addition of half the above quantity ot 

 sulphur, or 90 parts of sulphur and 100 ot iron, (= 4 7-36 

 per cent.;) but this opinion he appears to have formed in 

 consequence of results obtained by synthetical cxpetimcnis 

 made in the dry way. Now, when we consider liow dilii- 

 cult it is to regulate the high degrees of temperature, and 

 what a numerous chain of alterations in the relative order 

 of affinities most commonly result from alterations in these 

 degrees of heat, it seems to me that we cannot rely, with 

 absolute certainty, on synthetical experiments made in the 

 above way, unless they are corrected, and contrasted with 

 analytical experiments made on the same substances, but 

 it does not appear, from the two memon-s pubhshcd by 

 Mr. IVoust, to which I have so frequent y alluded, (hat 

 that "cnlkman did more, in respect to analysis, tiiantlist.i 

 <^ C) 1 "le 



