142 Br. R. B. Thomsons Chemical [Feb. 



Article VII. 



Chemical Analysis of Crucilite, a new form of peroxide of 

 Iron. By Robert D. Thomson, M. D. 

 """ -— * vc 

 Iron is such an important metal, that every particular con- 

 nected with its natural history must be received with plea- 

 sure, both by the manufacturer and the man of science. It 

 is from this consideration that I venture to describe a new 

 form in which I have met with it occurring native, in com- 

 bination with its saturating dose of oxygen. 



Previous to doing so, however, it may be observed, that 

 there are four principal states in which the peroxide of iron 

 has been hitherto found , which it may be proper to enumerate . 



1 . Anhydrous peroxide of iron, or anhydrate or specular 

 iron ore, the primary form of which is a rhombohedron, and 

 whose composition may be represented by/. 



2. Hydrous peroxide of iron, or perhydrate of iron. Its 

 primary form is a scalene four-sided pyramid, and its sign 

 /+Aq. 



3. Dihydrate of iron, which has not been noticed in mi- 

 neralogical books, but has been examined by Dr. Thomson. 

 A massy specimen from his cabinet which I analyzed pos- 

 sessed a spec. grav. of 4*016, dissolved with some difficulty 

 in aqua regia, and consisted of 



Peroxide of iron - - - - 77*48 



Lime 6*41 



Silica 6*00 



Peroxide of manganese - - 1*50 



Water - - 8*50 



99*89 

 Now this is equivalent to 



Peroxide of iron 2 atoms 

 Water - - - 1 atom 

 and the formula which expresses this composition is 2/ 

 + Aq. 



4. Magnetic iron ore, consisting of 1 atom of protoxide 

 and 2 atoms peroxide of iron. 



During the course of last year, the variety which has 

 been already alluded to was brought from Ireland by Mr. 

 Doran, the mineral dealer. It was seated in sandstone, the 



