Measurements of lattice parameters and room-temperature magnetic susceptibilities were carried out on solid solutions of gold, aluminum, indium, tin, and zirconium in platinum. The results of the X-ray analysis indicate a range of primary solid solutions of aluminum, indium, and tin in platinum extending at 1000 degree C up to 11, 10 and 7 at. %, respectively. The magnetic data of the various systems can be represented by a common curve when plotted against the valence electron concentration. This result is consistent with the idea that the valence electrons of the solute atoms are transferred to the electron gas of the alloys. The electronic structure of the alloys is discussed.