A physico-chemical study of sodium amalgams. Part II. The electrical conductivity
Transactions of the Faraday Society
Previous work has shown that the thermal diagram for sodium amalgams is very complex.:: Not only are several compounds shown to exist, but some of these compounds undergo polymorphic changes in the solid state. The investigation of the specific volumes of the solid and liquid alloys added but little to our present knowledge of these substances. It was thought desirable to examine some other physical property which would be likely to show abnormal values when compound formation or polymorphic
... n or polymorphic change occurred. Guertler has pointed out the great importance of electrical conductivity measurements for determining the constitution of al1oys.f Such measurements have already been made for liquid sodium amalgams by Bornemann and Muller.1 Evidence was obtained of the existence in the liquid state of one compound only, viz., NaHg,. No reliable measurements of the electrical conductivity of the solid sodium amalgams have been made. The resistances of a few alloys were determined by Grimaldi,$ but the number examined was totally inadequate for drawing any conclusions as to the constitution of the alloys. The present Paper deals with the determination of the electrical conductivities of about twenty alloys at room temperature. The composition of the amalgams varied from pure sodium to 54 atoms per cent. of sodium. The electrical resistance of sodium is much less than that of mercury, so in order to obtain accurate values a long narrow thread of metal must be obtained. A capillary glass spiral I mm. diameter and a metre in length (when unwound) was used. At the ends of the spiral small bulbs were blown, into which were sealed platinum terminals. A glass tap was sealed to one end of the spiral; the other end terminated in a piece of wide glass tube left open. The resistance of the mercury between the platinum terminals was measured. The spiral was then filled with the liquid amalgam, using the arrangement previously described for filling pipettes in determinations of the specific volumes. I] The liquid amalgam was allowed to cool slowly in the vapour jacket. I t * Trans. Faraday SOC., vii., 1911. t Zeit. anorg.