40 0. C. Farrington — Action of Copper 



ever, gave no deposit at all, though left twenty-four hours in 

 the solution. With the exception of Knoxville and josephinite 

 the period required for deposition seemed to correspond quite 

 closely to the percentage of nickel. Thus ordinary iron would, 

 as it is well known to do, take on a coating of copper almost 

 instantly upon immersion in the solution. For the native iron 

 of Greenland, which contains 2 or 3 per cent nickel, about 

 thirty seconds were required. Irons like Charcas, Braunau, 

 Bemdego and Lexington Co., which contain 4 to 6 per cent of 

 nickel, required from one to two minutes, and Cape of Good Hope 

 and Babb's Mill, which have about 15 per cent of nickel, three 

 to four minutes. The somewhat eccentric Knoxville is a mete- 

 orite with a high percentage of nickel and josephinite contains 

 72 per cent nickel. Incidentally, therefore, the experiments 

 indicated that immersion of an iron-nickel alloy in a solution 

 of copper sulphate will afford a rough test of the percentage 

 of nickel contained in the alloy, and, since a meteorite must 

 contain nickel, a quick means of distinguishing meteoric from 

 terrestrial iron. 



To the experiments made in the above manner as compared 

 with those of Wohler, the objection may be made that Wohler 

 described his solution as a " Losung von neiitralem schwefel- 

 sauren Kupferoxyd^'' while a solution of copper sulphate has 

 normally an acid reaction. In order to remove doubt on this 

 point a solution was prepared according to the method given 

 by Blair.* Such a solution is one of 200 grams to the liter, 

 but to it sodium hydroxide is added until a slight precipitate 

 appears and the latter is removed by filtration. The solution 

 still has an acid reaction, but the possible presence of free acid 

 is avoided. 



The sections immersed in this solution gave, however, as far 

 as could be observed, results exactly similar to those obtained 

 with the simple solution. As no mention is made by Wohler 

 or other investigators of treatment to reduce the acidity of 

 their solutions, it is highly probable that only the simple solu- 

 tion was used. Employment of solutions of different strengths 

 was likewise without effect on the results obtained. Tests 

 were made with a solution of 100 grams to the liter and some 

 intermediate strengths, but the fact of the deposition of the 

 copper and the period required for its deposition seemed 

 unchanged. 



Different temperatures were however of considerable influ- 

 ence in changing the time required for deposition. Thus the 

 cube nickel, which required thirty minutes at 18° C, reduced 

 copper in five minutes when the solution was heated to 63° C. 



* The Chemical Analysis of Iron, 3d ed. , p. 63. 



