42 0. C. Farrington — Action of Copper Sulj^hate, etc. 



if heated a moment before immersion. This is probably on 

 account of the fihn of oxide formed. The sections of Cape 

 of Good Hope and Knoxville, which had an active behavior 

 as treated ordinarily, I found to be thoroughly passive when 

 reimmersed without rubbing after an interval of two weeks. 

 1^0 perceptible film of oxide could be detected, but on rubbing 

 the surface with emery cloth deposition took place as before. 

 There are some indications again that the molecular condition 

 of the substance and especially of its surface may determine its 

 degree of activity. For instance, a cube of nickel which was 

 perfectly passive when treated in the ordinary way, no deposit 

 being formed on it after standing 24 hours in the sulphate 

 solution, although fresh surfaces were frequently exposed by 

 abrasion, was made active by being heated to redness, cooled 

 and again made bright by abrasion. A deposit of copper then 

 formed within twenty minutes and the cube has shown active 

 behavior since. The activity was the same both when the 

 cube was cooled slowly and quickly. The specimen of josephi- 

 nite previously mentioned as being passive at ordinary tem- 

 peratures, was given a similar treatment, i. e., heated to 

 redness, cooled and rubbed. It also became active under this 

 treatment, reducing copper in a solution at the temperature of 

 18° C. at some time within a period of twelve hours, the exact 

 time not having been noted. It was noticeable in this case, as 

 in many others, that deposition began and was most active 

 about capillary cracks and fissures. This would indicate that 

 capillary tension was infiuential in effecting the reduction of 

 the copper, and it is reasonable to suppose that such would be 

 the case, since the molecules are probably brought into closer 

 contact in such situations. It is evident that several conditions 

 may affect the degree of activity of a meteorite or any other 

 iron-nickel alloy, but I have found nothing to accord with 

 Wohler's observation that passive meteorites which had been 

 made active by contact with iron, after the reduced copper 

 was filed off became again passive. While several phases of 

 the subject invite further investigation, enough evidence seems 

 to be obtained to warrant classing all meteorites as active to 

 copper sulphate and dropping the designation of passive 

 meteorites. 



I am indebted to my associate, Mr. H. W. ]S"ichols, for a 

 number of useful suggestions during the progress of the 

 investigation. 



Field Columbian Museum, Cliicago, 111. 



