The Humboldt Hydrometer Water Bath is designed to provide a 68°F (20°C) ambient temperature throughout the unit by using a microprocessor-based temperature control with integral heater and chiller. The control processor in the bath provides a consistent bath temperature of 68°F (20°C) accurate to within 0.1% of input span ±1°F. Temperature range can be set between 50°F (10°C) and 120°F (49°C). The water bath is fully-insulated and includes a circulating pump, which ensures a constant water temperature throughout bath. While the Hydrometer Jar Water Bath can be used for many uses within labs, it was designed specifically for use in providing a consistent temperature bath for storing hydrometer jars in accordance with ASTM D422, AASHTO T88 and UNE 103.102 to determine the particle size distribution of very fine materials, such as silt and clay. The H-4239A can accommodate (8) hydrometer jars at a time. All models include a stainless steel shelf, which supports specimens while allowing 2" of free circulating water above and below specimens.