DecAiuijHjsition <if Iroit Py riles. 131 



tlie radiated ]\vrites, I might be iiiduecd to adopt the contrai'V 

 oi)iiiioii."' 



" But I am inolined to attribute the effect of vitriolization ob- 

 served ill some of the ])vrites. not so much to the proportion, as 

 to tlie state of the sul})]iur in tlie compound ; for I much sus- 

 ])ect, that a predisposition to viti-iolization, in these i)yrites, is 

 jiroduced by a small portiou of oxvgen being ])reviously com- 

 bined with a part, or witli the general mass of the suli)hur, at 

 1 lie time of the original formation of these substances, so that 

 the state of the sulphur is tending to that of oxide, and thus the 

 accession of a farther addition of oxygen becomes facilitated." 



0. luterinixture loiih pijn-liotHe ur iron protosulphidc. The 

 attention of Berzelius was early called to these interesting })he- 

 nomena of decomposition, and in a paper^ on White Pyrites, he 

 states : *' if this pyrites is not regularly crystallized, it becomes 

 covered with an efltiorescence of vitriol, and is at last completely 

 decomposed into it. This result is certainly to be attributed to 

 a mixture of magnetic ])yrites."' However, even in the same ]ia- 

 ])er he presents an analysis of such a ciystal, in which the 

 only variation from the normal constitution consisted in the 

 ])resence of 0. TO ])er cent of manganese and 0.80 per cent of 

 silica. 



A few years latei', he made experiments on the same subject, 

 whose results are thus described :'" '' The white jn'rite consists 

 of two varieties, of whicdi one, perfectly crystallized, remains un- 

 altered in the air, while the other, whicli presents a confused 

 crystallization, eflfloresces on exi)osure to the air and falls into a 

 jiowder, evidently of the character of a vitriol. This phenom- 

 enon therefore proves a difference of composition between these 

 varieties — a difference which is worthy of study in order to as- 

 certain whetlier it is of a character which may explain the differ- 

 ence of both from yellow pyrite."' Of the latter of the two va- 

 rieties he allowed a fragment to efHoresce 2| years, and exam- 

 ined it after its complete disintegration. 



'' Its volume was nearly doubled ; it was fissured in every di- 

 rection, and fell to pieces at the slightest touch. A part of its 



1 Scbweigo-., Jour. Cli. Phys., (1819), XXVI. 67. 

 - Ann. Ch. et Phys., (1822), XIX. 440. 



