Wednesday, September 17, 2008

Water Bath

Device that maintains water at a constant temperatureElectrically heatedHas a thermostatic temperature regulatorProvide temperature ranging from room temperature to 100◦C. Various sizes to suit various workloads are available. Types of water bath.

Unstirred water baths

The cheapest laboratory baths Least accurate temperature control because the water is only circulated by convection and so is not uniformly heated.

Stirred water baths

Have more accurate temperature control.In-built pump/circulator or a removable immersion thermostat / circulator (some of which can pump the bath liquid externally into an instrument and back into the bath).

Shaking water baths

Have a speed controlled shaking platform tray (usually reciprocal motion i.e. back and forwards, although orbital motion is available with some brands) to which adaptors can be added to hold different vessels.

Cooled water baths

Available as either an integrated system with the cooling system (compressor, condenser, etc.) built into the laboratory water baths or using a standard water bath as above using an immersion thermostat / circulator with a separate cooling system such as an immersion coil or liquid circulated from a circulating cooler.

Boiling water baths

Usually designed with an analogue control to control water temperature from simmering up to boiling and have a water level device so that the bath does not run dry and an over temperature cut-out thermostat fitted to or near the heating element.

Cooling circulators

Vary in size, cooling capacity / heat removal, temperature accuracy, flow rate, etc. and are used to cool laboratory water baths or remove heat from another piece of equipment by circulating the cooled water / liquid through it and back to the circulator 1

Water Bath Controls Temperature Control: All water baths have a control to set temperature. This control can be digital or a dial. Often there is an indicator light associated with this control. When the light is on the water bath is heating. When the water bath reaches the set temperature, it will cycle on and off to maintain constant temperature.

Safety Control: Most water baths have a second control called the safety. This control is set at the maximum temperature the water bath should attain. It is usually set just above the temperature control. Often an indicator light is associated with the safety control. If the water bath reaches the temperature that the safety control is set at, the light will go on. It will be impossible for the water bath to heat higher than the safety setting even when the temperature setting is higher. If your water bath stays a temperature lower than the temperature control setting, try increasing the safety control setting.

Shaking Control: Shaking water baths have additional controls for shaking. The shaking mechanism can be turned on or off. The speed of shaking can also be set. Cultures grown in liquid media are often shaken to allow constant mixing with air and oxygen with the culture

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