On the Mcctrical Resistivity of Electrolytic Nickel. 51 



as required in a state of such chemical piu:'ity, and brought so easily 

 into similar physical conditions as to annealing and density, that 

 determinations made by different observers of their resistivity or 

 specific electrical resistance are nearly identical. 



Matthiessen's long-accepted value"^ for the m.ass resistivity of copper 

 in the form of hard-drawn wire, viz., 0-14493 standard ohm per 

 metre-gramme, was substantially confirmed by the more recent work 

 of Mr. T. C. Fitzpatrick.f Even the pm-est electrolytic copper now 

 obtainable in an annealed condition does not show an electric con- 

 ductivity more than 3 per cent, greater than that of a similar character 

 prepared thirty-five years ago by IMatthiessen. 



In a research carried out in the years 1892 and 1893 by the author 

 in conjunction . with Professor Dewar, careful redeterminations were 

 made of the volume-resistivity at 0' C. of all ordinary metals, taken 

 for the most part in an annealed condition and in a state of great 

 chemical purity. 



The values so obtained for the electrical volume-resistivity of silver, 

 copper, gold, aluminium, zinc, platinum, tin, lead, magnesium, and 

 iron agreed fairly well with the values given by Matthiessen, and 

 quoted in most of the treatises on electricity. The resistivity of cad- 

 mium, as given by us was, however, considerably larger than that 

 usually stated, although our sample of cadmium was very carefully 

 prepared. 



In the case of nickel, the purest nickel we were able to obtain was 

 that prepared from nickel-carbonyl. Dr. Luclwig Mond, F.E.S., was 

 so kind as to furnish us with two tubes of this nickel. It was found, 

 however, to be too brittle to draw into wire, and the operation of 

 melting it would have most certainly introduced impurities. Accord- 

 ingly, the nickel tube was cut up in the lathe into a spiral, and a 

 resistance coil formed with it which could be used for taking the 

 resisti"\aty ratios at different temperatures, but which was not suffi- 

 ciently uniform in dimensions to permit its volume-resistivity to be 

 calculated. Hence, in our published results, w-e took the volume-re- 

 sisti^dty of this nickel at 0° C. to be 12,320 C.G.S. units, which is the 

 value given by Everett, said to be derived from ^latthiessen's experi- 

 ments, and simply calculated the resistivity at other temperatures 

 from the experiments given by our own observations with the Mond 

 nickel. About a year ago, however, Mr. J. W. Swan, F.E.S., sent me 

 a sample of nickel wire which he had prepared electrolytically from a 

 hot solution of very carefully piu-ified nickelous chloride. The electro- 

 lytic metal was annealed by heating in an atmosphere of hydrogen, 

 after having been drawn into wire through a die. 



The nickel wire so prepared and annealed is as soft as a silver wire. 

 * See ' B.A. Report,' 1864, or ' Phil. Mag.,' 1865. 



t See ' B.A. Report,' Leeds, 1890, or ' Electrician,' vol. 25, p. 608, 1890. 



