Semiconductor processing systems and methods are provided in which an amount or concentration of a chemical in a chemical mixture contained in a tank is automatically controlled based on a sensed properties of the chemical mixture. In some embodiments, a semiconductor processing system includes a processing tank that is configured to contain a chemical mixture. A chemical sensor is configured to sense one or more properties of the chemical mixture. The system further includes an electrically controllable valve that is configured to adjust an amount of the first chemical in the chemical mixture based on the sensed one or more properties of the chemical mixture.