Iron. 



colour, of a radiated or foliated texture, 

 of a moderate hardnefs, and fometimes fo 

 brittle, as to be eafily broken between the 

 fingers, but very weighty fince its fpecific 

 gravity is 7,119 ; when fcratched it fhews a 

 red trace, which diitinguiflies it from tung- 

 ften. It is fcarcely folubb in acids, and of 

 very difficult fulion. According to, Lehman* 

 it confifts of filiceous Earth, calx of iron, and 

 a fmall proportion of that of tin, Chym. Schrift* 

 356, and from his experiments, I am incli- 

 ned to think it contains manganefe. 



SPECIES XXV. 

 Native Prujfian Blue. 



39. It confifts of play mixed with iron, 

 and fome unknown tinging fubftance, gene- 

 rally found in fwampy grounds or bogs. 

 It is at firft white but when expofed to the 

 air, it becomes either of a light or deep blue. 

 When heated, it turns greenifh, and emits 

 a flight flarne, and then becomes red and 

 magnetic, it is foluble both in acids and 

 Alkalis, but the latter precipitate it from the 

 former, and the former from the latter ; 

 the precipitate is at firft greenifli, but gra- 

 dually aflumes a white hue, but recovers its 

 falue tinge if it be fteeped in vegetable aftrin- 

 gents, Ber^m. Sciagr. . 206. Phil* Tranfi 



1768 



