A water bath is laboratory equipment made from a container filled with heated water. It is used to incubate samples in water at a constant temperature over a long period of time. Most water baths have a digital or an analogue interface to allow users to set a desired temperature, but some water baths have their temperature controlled by a current passing through a reader. Uses include warming of

reagent In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...

s, melting of substrates, determination of

boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envi ...

, or incubation of cell cultures. It is also used to enable certain chemical reactions to occur at high temperature. Water baths are preferred heat sources for heating flammable chemicals, as their lack of open flame prevents ignition. Different types of water baths are used depending on application. For all water baths, it can be used up to 99.9 °C. When the required temperature is above 100 °C, alternative methods such as oil bath,

silicone oil A silicone oil is any liquid polymerized siloxane with organic side chains. The most important member is polydimethylsiloxane. These polymers are of commercial interest because of their relatively high thermal stability and their lubricating prop ...

bath or sand bath may be used.

Precautions

It is not recommended to use water bath with

moisture Moisture is the presence of a liquid, especially water, often in trace amounts. Moisture is defined as water in the adsorbed or absorbed phase. Small amounts of water may be found, for example, in the air (humidity), in foods, and in some comme ...

sensitive or

pyrophoric A substance is pyrophoric (from , , 'fire-bearing') if it ignites spontaneously in air at or below (for gases) or within 5 minutes after coming into contact with air (for liquids and solids). Examples are organolithium compounds and triethylb ...

reactions. Do not heat a bath fluid above its flash point. Water level should be regularly monitored, and filled with distilled water only. This is required to prevent salts from depositing on the heater.

Disinfectant A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than ...

s can be added to prevent growth of organisms. If application involves liquids that give off fumes, it is recommended to operate water bath in fume hood or in a well ventilated area. The cover is closed to prevent evaporation and to help reaching high temperatures.

Types of water bath

Circulating water baths

Circulating water baths (also called ''stirrers'' '')'' are ideal for applications when temperature uniformity and consistency are critical, such as

enzymatic An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as produc ...

and serologic experiments. Water is thoroughly circulated throughout the bath resulting in a more uniform temperature.

Non-circulating water baths

This type of water bath relies primarily on

convection Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoy ...

instead of water being uniformly heated. Therefore, it is less accurate in terms of temperature control. In addition, there are add-ons that provide stirring to non-circulating water baths to create more uniform heat transfer.

Shaking water baths

This type of water bath has extra control for shaking, which moves liquids around. This shaking feature can be turned on or off. In

microbiological Microbiology () is the scientific study of microorganisms, those being of unicellular (single-celled), multicellular (consisting of complex cells), or acellular (lacking cells). Microbiology encompasses numerous sub-disciplines including virol ...

practices, constant shaking allows liquid-grown

cell cultures Cell culture or tissue culture is the process by which cells are grown under controlled conditions, generally outside of their natural environment. After cells of interest have been isolated from living tissue, they can subsequently be main ...

grown to constantly mix with the air. Some key benefits of shaking water bath are user-friendly operation via keypad, convenient bath drains, adjustable shaking frequencies, bright LED-display, optional lift-up bath cover, power switch integrated in keypad and warning and cut-off protection for low/high temperature.

Water bath technologies

The bath is a fundamental product in any laboratory. Over the years, water baths have evolved from basic analog tools to advanced digital machines capable of sophisticated and programmable controls, functions, and capabilities. Key features in water baths often include: * Multi-language operation * User-settable limit values * "Eco modes" which save energy after set programs are completed * User-settable alarms: audible, visible or both * Displays of actual and/or set point temperatures * Programmable pre-sets for frequently used temperatures * Integrated timers * Hinged gable covers * Calibration off-set capabilities * Stainless reservoirs * Reservoir drains * Primary and automatic safety thermostats * Compatible with waterless alloy bath beads

Additional images

File:WaterBath.jpg, LWIA seawater cleaning methods; water bath with injector block, septum support and insert. File:Water bath adjustment knob 2015.jpg, Temperature control knob of a water bath File:Inside water bath.JPG, Inside water bath with micro-centrifuge rack File:Floating Rack for Water Bath (5544004133).jpg, A water bath float rack.

References

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