MR. HATCHETT ON MAGNETICAL PYRITES. 1^ 



fron filings, lie diftiiled the fulphuret with an additional quan- 

 tity of fulphur, in an inferior degree of heat, and obtained 

 378 grains of a fubdance which, excepting denfity, was fmii- 

 lar to the common martial p) riles.* 



It i^ however to be regretted, that Mr. Prouftdidnot make He did not maia 

 a regular analyfis of the pyrites of Soria, and of the refiduum ^^^^^ ^ ^"*^* 

 'after diliiliation ; for(unlefs thefe pyrites are very differentfrom 

 thofe which C have examined) he would moft probably have 

 foui^d the proportion of fulphur greater than that which he has 

 aflign^d to natural pyrites in general. This at leaft there is great 

 reafon to fuppufe, if we allow that moft or all of the pyrites 

 have been formed in the humid way, by which, we may con- 

 ceive, a larger proportion of fulphur may be introduced into 

 the compound, than can take place in high degrees of tem- 

 perature. And tiiis opinion is corroborated by the refults of 

 my analyfes; for, inftead of finding the general proportions to * 



be 47.36 of fulphur and 52.6 !• of iron, the mean refult of thefe 

 analyfes is very nearly the reverfe, being 53.24- of fulphur and 

 46.76 of iron. 



Mr. Proufi isalfo of opinion, that the pyrites which contain Prouftappr«- 

 the fmalleft quantity of fulphur, are thofe which are moft liable i^.^nds thatpy- 



. ^ ^ ^ ^ r ' rjjes holding the 



to vitriolizalion ; and, on the contrary, that thofe which contain leaft fulphur arc 



the largeft proportion, are the leaft affected by the air or "^®^ l^^^^^ ^^ 



weather. f This opinion of the learned profeflfor, by no means 



accords with fuch obfer vations as I have been able to make ; for 



the cubic, dodecaedral, and other regularly cryftallized pyrites, 



are liable to oxidizement, fo as to become what are called 



hepatic iron ores, but not to vitriolization; whilft the radiated 



pyrites (at leaft thofe of this country) are by much the moft 



fubjed to the latter effect; and therefore, as the refults of the 



preceding analyfes (liow that the cryftaHized pyrites contain 



lefs fulphur than the radiated pyrites, I might be induced to 



adopt the contrary opinion. But I am inclined to attribute the 



effect of vitriolization obferved in fome of the pyrites, not fo 



much to the proportion, as to the ftate of the fulphur in the 



compound; for I much fufped, that a predifpofition to vitrio- Sutthis dlfpo- 



lization, in thefe pyrites, is produced by afmall poi'tion ofo>ivgen ^bl^y aTlfe^ l^ 



being previoufly combined with a part, or with the general mafs, a coinraence- 



* Journal de Phyfique, Tome LIV. p. 92. 

 t Journal de fhyfique^ Tome LIII. p. *?1. 



5 of 



ment ot oxida- 

 tion. 



