Sulphate upon Iron Meteorites. 41 



The specimen of josephinite which reduced no copper at 18° C. 

 gave a deposit in twenty minutes at 63° C. At temperatures 

 below 18° C. the time required for the deposit is greatly 

 increased. Thus, Canon Diablo, which reduces copper in one 

 minute at 18° C, required sixty minutes at 10° C. and at 0° C. 

 was kept twelve hours without producing a deposit. Toluca, 

 which acquires a deposit in two minutes at 18° C, required 

 eighty minutes at 10° C. and at 6° C. was kept for four hours 

 without receiving a deposit. It was not tried longer at this 

 temperature. 



In these tests it was found necessary to immerse the sections 

 in water of the temperature whose effect it was desired to 

 study, for some minutes before transferring to the copper sul- 

 phate solution. Otherwise the heat of the section would cause 

 deposition at an earlier period. Also a fresh section which 

 had not been exposed to copper sulphate must be used, as 

 traces of a previous deposit of copper would hasten deposition. 



The periods named as sufficient for deposition are in all 

 cases somewhat approximate and variable, since the exact 

 moment at which deposition begins can be determined only 

 roughly by the eye. The general results are however suffi- 

 ciently accurate for the purpose. They show nothing to sup- 

 port Wohler's belief that certain meteorites are inherently 

 passive, but on the contrary point to the conclusion that mete- 

 orites act like any other iron-nickel alloy. 



Daubree considers the deposition of copper due to the fact 

 that the different alloys in a meteorite form electric couples,^ 

 but it hardly seems necessary to appeal to this force when 

 deposition takes place so quickly upon a piece of iron not 

 made up of different alloys. 



It is hardly essential to the purposes of this article to try to 

 account for the results reported by Wohler and other observ- 

 ers, but one or two suggestions may be made in this connec- 

 tion. It is possible that some of the surfaces tested by these 

 observers may have been rendered passive by treatment with 

 nitric acid. This was quite probably the case with Misteca as 

 treated by Bergemann, for he reports that upon freshly dis- 

 solved {gelost) pieces he could get no deposit, while pieces 

 from the outer surface of the meteorite without luster and of 

 dark gray color were quickly coated. f Wohler, however, 

 expressly states that the sections which he tested had not come 

 in contact with nitric acid. 



Again a slight film of grease or oxide may have prevented 

 deposition of copper. A substance so active to copper sul- 

 phate even as iron will be found to have become passive, 



* Comptes Rendus, 1867, vol. Ixiv, p. 685. 

 f Pogg. Ann., 1857, vol. c, p. 246. 



