Abstract
In this part of the paper the variations of lattice-parameter with the composition of the alloys is considered. Twenty alloys in the γ phase ranging in composition from 23 to 97 atomic per cent of nickel, and four alloys in the α phase ranging in composition from 3 to 16 atomic per cent of nickel were studied at different temperatures. At room-temperature, when iron is added to nickel the nickel lattice expands almost linearly with the atomic composition until the lattice-parameter reaches a maximum value of 3.5895 A. for an alloy the composition of which is 39 atomic per cent of nickel. On further addition of iron the lattice contracts. The variation of the parameter of the γ alloys with composition was examined at temperatures ranging up to 600°C. From the values of the lattice parameters the densities of pure iron-nickel alloys over the whole range of composition from pure iron to pure nickel were calculated.