The general problem of mass transfer from a solid spherical surface in a fluid is discussed following consideration of the flow patterns around a sphere and actual dissolution of solid spheres in a controlled stream of water. Experimental mass-transfer data for the dissolution of 0∙5 in. benzoic acid spheres in a stream of water at room temperature are correlated by the equation Kd / D = 44 + 0∙48 R 0∙5 S 0∙33 , where K is the mass-transfer film coefficient, d the sphere diameter and D the diffusivity. From a consideration of mass transfer by natural and forced convection, the following general equation is proposed for the mass transfer from solid spheres in a fluid: Kd / D = 0∙50 (G' S) 0∙25 + 0∙48 R 0∙5 S 0∙33 for G' S ⊀ 10 5 .