Abstract: An acid bath including an inner vessel, having non-opaque wall sections, is sealingly mounted within an outer housing with electric heating elements mounted therebetween. A condensing lid is mounted to enclose the inner vessel to prevent escape of acid fumes therefrom, an optical-type sensor is mounted to transmit and receive optical signals through the non-opaque walls to determine liquid level within the vessel.

Abstract: A nitride etch bath having an inner vessel encapsulated within an outer housing with an electric heating element sandwiched therebetween. A condensing collar is heat sealed about the top of the inner vessel and supports a condensing lid hinged to the collar. The condensing lid includes an array of enclosed channels and canals in the top and bottom of the lid for transporting a condensing medium. As acid is boiled in the inner vessel, hot acid water vapors rise and impact the condenser lid which condenses the vapors to a liquid utilizing the condensing medium to cool the lid surface. The condenser lid and collar seal the inner vessel to prevent vapor leakage.