Nickel powder, and nickel boride (Ni-B) and nickel phosphide (Ni-P) alloy particles prepared by aqueous chemical reduction, were studied by microcalorimetry. Treatment of Ni powder, Ni-B, and Ni-P in H-2 at 623 K was sufficient to produce reduced nickel surfaces for chemisorption. After treatment, these samples were shown by X-ray diffraction to be crystalline. The presence of B and P increased the BET surface areas to values of 8.4 and 19.7 m(2)/g, respectively, compared to the value of 1.7 m(2)/g for Ni powder. Microcalorimetric measurements of CO and H-2 adsorption performed at 308 K on reduced Ni powder exhibited initial heats of 120 and 85 kJ/mol, respectively. The presence of B decreased the initial heats of CO and H-2 adsorption by 20 and 10 kJ/mol, respectively and decreased the saturation uptakes of these molecules per unit surface area. The presence of P decreased the initial heats of CO and H-2 adsorption by 30 and 20 kJ/mol, respectively, and also decreased the saturation uptakes of these molecules per unit surface area.