

[ 477 ] 

 LXVIII. Intelligence and Miscellaneous Articles. 



ON THE PASSIVE STATE OF METEORIC IRON. 

 BY PROF. WOHLER. 

 T HAVE observed the remarkable fact that the greater portion of the 

 -*- meteoric iron which I have had the opportunity of examining, is in 

 the so-called passive state, that is to say, that it does not reduce the 

 copper from a solution of neutral sulphate of copper, but remains 

 bright and uncoppered on immersion therein. But if touched in the 

 solution with a piece of common iron, the reduction of the copper 

 commences immediately upon the meteoric iron. It also becomes 

 active instantaneously on the addition of a drop of acid to the solu- 

 tion of copper ; but if the reduced copper be filed away, the new sur- 

 face is again passive ; indeed I was unable by filing away to pro- 

 duce an active or reducing surface on any passive meteoric iron. I 

 convinced myself by experiments on meteoric iron, which had never 

 been in contact with nitric acid and nevertheless was passive, that 

 this state could not have been produced by the corrosion of the sur- 

 face by the acid for the production of the Widmanstattean figures. 



I thought at first that this deportment might be employed as a 

 means of distinguishing true meteoric iron ; but it soon appeared 

 that some undoubtedly genuine meteoric iron was not in this state. 

 In this respect I have observed the following differences : — 



The Pallas iron, the iron which fell at Braunau in 1847, that of 

 Schwetz, Bohumilitz, Toluca, Green County (N. America), Red 

 River, and that from the Cape of Good Hope, are passive. 



The iron from Lenarto, Chester County, Rasgata, Mexico, Senegal 

 and Bitburg (the latter forged), is active or reducing. 



Between the two stands the iron from Agram, Arva, Atacama and 

 Burlington (N. America), which do not become coated with copper 

 immediately, but on which the reduction gradually commences after 

 a longer or shorter contact with the cupreous solution, and usually 

 from one point or from the margins of the fluid. 



These peculiarities appear to have no connexion either with the 

 presence of nickel or the property of forming regular figures on cor- 

 rosion, as is shown by the iron from Lenarto, which is active, although 

 it contains 8 - 45 per cent, of nickel and - 66 of cobalt, and exhibits 

 the most beautiful figures on corrosion, and also by the iron brought 

 by Boussingault from Rasgata in Columbia, which, according to my 

 analysis contains 6"74 per cent, of nickel and 023 of cobalt. On 

 the other hand, the iron from Green County, which is completely 

 passive, contains 19 per cent, of nickel and exhibits no figures. 



I also found that an artificially prepared alloy of iron and nickel, 

 which on corrosion acquired a damasked surface, reduced the copper 

 from solution in the same manner as common iron. 



Whether this state is proper to all meteoric iron on its reaching 

 the earth, and, as may have happened in the case of the active kinds, 

 have only been lost in the course of perhaps a very long period of 

 time, and what probable opinion can be formed of these phamo- 

 mena, must be settled by experiments and observations of a more ex- 

 tended nature. — PoggendorfF's Annalen, vol. lxxxv. p. 449. 



