## Abstract

An apparatus is described which makes possible the rapid determination of the temperature variation of the magnetic susceptibilities of small solid specimens. The deflexions of a beam of light passing through a Sucksmith balance are recorded photographically. The temperature of the specimen, measured by a Au-Co/Ag-Au thermocouple in contact with it, is initially reduced to 20 degrees K and deflexions are recorded at small intervals of temperature as the temperature of the specimen rises to 290 degrees K. The whole temperature range can be covered in 4 h. The mean deviation of single measurements from the best smooth curve passing through them is less than 0$\cdot $2% of the mass susceptibility of the specimens. The apparatus has been used to measure the temperature variation of the susceptibilities of spectrographically standardized specimens of platinum, rhodium and palladium. Measurements on three pure palladium specimens show a maximum in the susceptibility temperature curve at 80 degrees K. The experimental results for platinum show a change in the curvature of the susceptibility temperature curve below 90 degrees K, the susceptibility increasing more rapidly as the temperature decreases. The experimental results for rhodium show a regular increase of susceptibility with increase of temperature. The results for palladium are discussed in relation to the collective electron treatment of metals, and assuming a parabolic distribution of energy states in the d band, estimates are made of the effective Fermi-Dirac degeneracy temperature $\theta _{F}$, the number of holes per atom, q, and the exchange interaction energy $\theta ^{\prime}$ The estimated values are $\theta _{F}$ = 1020 degrees K, q = 0$\cdot $29, $\theta ^{\prime}$ = 554$\cdot $0 degrees K. Similar estimates are made in the case of platinum, the values being $\theta _{F}$ = 1750 degrees K, q = 0$\cdot $25, $\theta ^{\prime}$ = 770 degrees K.