Technical Abstract: The constant capacitance model, a chemical surface complexation model, was applied to boron, molybdenum, and arsenate, As(V), adsorption on up to 49 soils selected for variation in soil properties. The constant capacitance model was able to fit boron, molybdenum, and arsenate adsorption on all soils. General regression models were developed for predicting soil B, Mo, and As(V) surface complexation constants from easily measured soil chemical characteristics. These chemical properties were cation exchange capacity, inorganic carbon content, organic carbon content, aluminum oxide content, iron oxide content, and surface area. The prediction equations were used to obtain values for the B, Mo, and As(V) surface complexation constants for additional soils, thereby providing a completely independent evaluation of the ability of the constant capacitance model to describe adsorption. Incorporation of these prediction equations into chemical speciation-transport models will allow simulation of soil solution B, MO, and As(V) concentrations under diverse agricultural and environmental conditions without the requirement of soil specific adsorption data and subsequent parameter optimization.