130 Decomposition of Iron Pyrites. 



4. Feeble combination of the sulphur. In a footnote on tlie 

 paper of Berzelius, just referred to, the Editor, J. L. G. Mein- 

 ecke, objects that arsenic, manganese, etc., do not occur in all 

 the forms of white pyrite, and calls attention to its different 

 mode of crystallization, steel gray color, ready decay, and also 

 the fact that, " on nibbing it yields a strong sulphurous odor, 

 whereby, as well as by its weathering, it reveals a less intimate 

 combination with sulphur. From its ready decomposition and 

 its free sulphurous odor, it is clearly deduced that the sulphur is 

 not united to the iron in the same way as in pyrites." This 

 reasoning also api^ears too indefinite and insufficient. 



5. Undable condition of sulphur, through a little oxygen orig 

 inally combined. Among the earliest reported analyses of mar- 

 casite were those of Hatchett' in 1804, who advanced the follow- 

 ing view, in explanation of the tendency of that mineral to de- 

 composition, but one which remains uuconfirmed by later anal- 

 ysis. 



" The pyrites crystallized in regular figui-es, such as cubes and 

 dodecaedrons, according to the above analyses contain less sul- 

 phur, and more iron, than the radiated pyrites, and perhaps than 

 others which are not regularly crystallized. This difference, 

 however, is not ccnsid^'i-able ; for the dodecaedral pyrites which 

 afforded the snuillest quantity of sulphur of any of the regularly 

 crystallized ])yrites, yielded 5;^. 15 ; and the radiated pyrites, No. 

 5, gave 54. 31: ; the difference, therefore, is only 2.19." "Mr. 

 Proust is al.-o of oi)inioM, that the pyrites which contain the 

 smallest quantity of sulphur are those which are most liable to 

 vitriolization ; and, on the contrary, that those which contain 

 the largest proportion are the least affected by the air or weather. 

 Tliis opinion of the learned professor by no means accords with 

 such observations as I have been able to make ; for the cubic, 

 dodecaedral, and other regularly crystallized pyrites are liable 

 to oxidizement, so as to become what are called hepatic iron ores, 

 but not to vitriolization ; whilst the radiated pyrites (at least 

 those of this country), are by much the most subject to the lat- 

 ter effect ; and therefore, as the results of the preceding analy- 

 ses show that the crystallized pyrites conta-'n less sulphur than 



' Phil. Trans., (1804), XCIV, 826 and 340. 



