Laboratory Water bath Principle, Types, Parts, Operating Procedure, Uses

A water bath is laboratory equipment consisting of a heated water-filled container. It is utilised to incubate water samples at a steady temperature for an extended period of time. Some water baths have their temperature controlled by a current going through a reader. The majority of water baths allow users to specify a desired temperature via a digital or analogue interface. Utilizations include warming of chemicals, substrate melting, and cell culture incubation. It is also utilised to facilitate the high-temperature occurrence of certain chemical processes. As their lack of an open flame avoids ignition, water baths are the preferred method for heating combustible compounds. Various forms of water baths are utilised for various applications. It can be used for all water baths up to 99.9 °C. When the temperature exceeds 100 degrees Celsius, alternative treatments such as oil bath, silicone bath, and sand bath may be utilised.

What is Laboratory Water Bath?

A hot water bath or Laboratory Hot water bath is one of the essential instruments of a laboratory. It’s normally used for incubation of test samples underwater at constant temperature (hot or cold) over a long period of time.

A hot water bath features a large container with heated water. The design configurations, sizes, and dimensions of a hot water bath always varies. The container size of a laboratory water bath varies from12 liters to 32 liters for a standard model and 50 -100 liters for a large size water bath.

Its mainly used in clinical and microbiology laboratories, university’s lab, environmental research, and even food technology for warming reagents, sample thawing, corrosion tests and bacteriological examinations etc.

A water bath can heat a small amount of liquid sample for over a long period of time without changing the concentration of constituents by evaporation.

There are present different types of laboratory water baths and they are used depending on the applications.

When you require balanced high-temperature heating that no more than 100℃, a water bath is a good choice.

Definition of Laboratory Water Bath

A hot water bath or Laboratory hot water bath is one of the essential instruments of a laboratory, which contains a large container with heated water. It’s normally used for incubation of test samples underwater at constant temperature (hot or cold) over a long period of time without changing the concentration of constituents by evaporation.

Working Principle of a Laboratory Water Bath

The water bath’s working mechanism is relatively basic. A heating plate placed around the reservoir increases the water’s temperature. The operating mechanism of the water bath differs depending on whether it is analogue or digital.

Turning on the mains in an analogue water bath causes current to flow to the thermostat and subsequently to the water-immersed heater. When the water temperature falls below the calibrated threshold, the thermostat will allow current to flow through the heater. Consequently, the water’s temperature will begin to rise. Once the desired water temperature is reached, the thermostat will shut off. Therefore, a heating rod will not conduct electricity. As a result, the water temperature decreases, as evidenced by the heating light going out.

The digital water bath has a similar mechanism as the analogue water bath. In it, the PID controller and solid-state relay (SSR) regulate the heater’s current flow. When the water temperature is below the calibrated value, the controller will provide DC current to the relay. The relay will then be triggered, causing the heating rod to receive current. Consequently, the heater begins heating the water. The relay is activated and deactivated by the controller when the temperature reaches a predetermined value. As a result, the heating rod will be continually ON and OFF. Consequently, regulating the ON/OFF stage duration keeps the temperature constant in a digital water bath.

Similarly, digital water baths have a resistive temperature detector (RTD) that measures the temperature of the water and converts it to a resistance value for the controller. The controller compares the received value to the predetermined value.

Parts of laboratory Water Bath

1. Container or Tank Bath: In the container, the test samples are kept in hot water for a long period of time. The container of a  Laboratory Water Bath is made up of insulated metal such as stainless steel.
2. Container Lid: The lid helps to keep covering the container, so that water does not evaporate out of it. It’s mainly made up of heat resistant glass or insulated metal.
3. Heater: A laboratory water bath contains a Cu50 temperature sensor, which helps to generate heat.
4. Thermometer: This helps to check the temperature of the water bath. It can be inbuilt or placed individually.
5. Thermostat or regulator: A thermostat helps to maintain the temperature of a water bath at a constant level.
6. Propeller or stirrer device: It helps to circulate the water inside the water bath (Found in Circulating water baths).
7. Outlet: It helps to get the water out of the container.
8. Indicator light: All water bath should contain an indicator light. When the light is on the water bath is heating. If the water bath reaches the required temperature the light will be turn off to maintain the constant temperature.
9. Digital/analog interface: It allows the desired temperature of the water bath to be chosen.
10. Propeller/stirrer device: It is present in a continuous water bath and aids in the circulation of water within the container.

Controls of a Laboratory Water Bath

1. Temperature controller: All water baths contain a temperature controller it should be digital or dial. 
2. Safety Controler:  Most of the water baths contain a safety controller, which is mainly located above the temperature controller or associated with the indicator light. A Safety controller helps to set a maximum temperature which the water bath should attain. If somehow the water bath is able to reach the temperature which is set by the safety controller, then the safety light will be turn on. It is impossible for a water bath to reach the temperature higher than the safety settings even the temperature setting is higher. 
3. Shaking Controler: A shaking controller only found in a shaking water bath. This may allow us to speed up and stop or turn the shaker on.

Types of laboratory Water Bath

There are present different types of water bath. They are divide based on their applications.

1. Shaking water bath

A shaking water bath is a type of laboratory water bath that has a mechanism for shaking the samples being incubated. It consists of a container filled with water that is heated to a desired temperature using a heating element. The samples to be incubated are placed in tubes or containers and immersed in the water bath. The water bath has a mechanism for shaking the samples, which may be a motor-driven platform or a vibrating mechanism. The temperature of the water bath is typically controlled using a temperature control system.

Shaking water baths are commonly used for incubating samples that require mixing or shaking, such as cell cultures. They are also useful for incubating samples that require precise temperature control, as the circulating water helps to maintain a more stable temperature. Some shaking water baths also have built-in temperature controls and stirrers to help maintain a uniform temperature and mix the water.

Shaking water baths are commonly used in research and industrial laboratories, as they are able to maintain a uniform temperature and provide gentle shaking to the samples being incubated. They are also useful for incubating samples that require precise temperature control and mixing, such as cell cultures.

Applications of Shaking water bath

• Shaking water baths are utilised in a variety of food and beverage, material, and corrosion tests, as well as bacterial cultivation and molecular biology studies. Customize the shaking’s speed and/or frequency for better control.

Advantages of Shaking water bath

Some advantages of using a shaking water bath over a normal water bath include:

1. Improved mixing: The shaking mechanism in a shaking water bath helps to mix the samples being incubated, which can be beneficial for certain types of samples that require mixing or stirring.
2. Enhanced temperature control: The shaking mechanism in a shaking water bath can help to maintain a more uniform temperature throughout the bath, as the water is circulated by the shaking action. This can be beneficial for incubating samples that require precise temperature control.
3. Increased oxygenation: The shaking action in a shaking water bath can help to increase the oxygenation of the samples being incubated, which can be beneficial for certain types of samples that require oxygen.
4. Efficient incubation: The shaking mechanism in a shaking water bath can help to reduce incubation times, as the shaking action can help to accelerate certain reactions or processes.
5. Versatility: Shaking water baths can be used for a wide range of applications, including incubating cell cultures, enzymes, bacteria, and tissue cultures. They can also be used for maintaining the temperature of samples during experiments or reactions.

2. Circulating water bath

A circulating water bath is a type of laboratory water bath that has a pump and a heating element that work together to circulate the water and maintain a uniform temperature throughout the bath. The pump circulates the water from the bottom of the bath to the top, ensuring that all parts of the bath are evenly heated. The temperature of the water bath is typically controlled using a temperature control system.

Circulating water baths are suitable for incubating large volumes of samples at a constant temperature, such as enzymes, bacteria, and tissue cultures. They are also useful for maintaining the temperature of samples during experiments or reactions. Some circulating water baths also have built-in temperature controls and stirrers to help maintain a uniform temperature and mix the water.

Circulating water baths are commonly used in research and industrial laboratories, as they are able to maintain a uniform temperature over a longer period of time than non-circulating water baths. They are also useful for incubating samples that require precise temperature control, as the circulating water helps to maintain a more stable temperature.

Applications of Circulating water bath

• The circulating water bath is used to maintain a consistent temperature of water for incubating laboratory samples.
• Often referred to as “stirrers,” these devices are indispensable in settings where maintaining a constant temperature is crucial, such as in enzymatic and serologic research. The bath’s water temperature is more consistent because it is circulated thoroughly.

Advantages of Circulating water bath

1. Greater temperature stability: The circulating pump in a circulating water bath helps to circulate the water and maintain a more uniform temperature throughout the bath. This can be beneficial for incubating samples that require precise temperature control.
2. Larger volume capacity: Circulating water baths typically have a larger volume capacity than shaking water baths, making them suitable for incubating larger volumes of samples.
3. Gentle mixing: The circulating pump in a circulating water bath provides gentle mixing of the samples being incubated, which can be beneficial for certain types of samples that require mixing or stirring without being subjected to vigorous shaking.
4. Greater versatility: In addition to being used for incubating samples, circulating water baths can also be used for maintaining the temperature of samples during experiments or reactions. They can be used for a wide range of applications, including incubating cell cultures, enzymes, bacteria, and tissue cultures.
5. Durability: Circulating water baths are typically more durable than shaking water baths, as they do not have a shaking mechanism that is prone to wear and tear. This can make them more suitable for use in environments where the equipment is subjected to heavy use or vibration.

3. Non-circulating water bath

A non-circulating water bath is a type of laboratory water bath that does not have a circulating pump to circulate the water. It consists of a container filled with water that is heated to a desired temperature using a heating element. The samples to be incubated are placed in tubes or containers and immersed in the water bath. The temperature of the water bath is typically controlled using a temperature control system, and the water may be stirred using a stirrer to ensure a uniform temperature throughout the bath. Non-circulating water baths are suitable for incubating small volumes of samples at a constant temperature, such as enzymes, bacteria, and tissue cultures. However, they may not be suitable for incubating larger volumes of samples or for maintaining a uniform temperature over a longer period of time, as the water may cool down or become unevenly heated.

Applications of Non-circulating water bath

• This sort of water bath relies on convection rather than consistent heating of the water. Therefore, its temperature control accuracy is diminished.

Advantages of Non-circulating water bath

1. Simplicity: Non-circulating water baths are simpler in design and do not have a circulating pump, making them easier to use and maintain.
2. Lower cost: Non-circulating water baths are typically less expensive than circulating water baths, as they do not have the added complexity and cost of a circulating pump.
3. Suitable for small volumes: Non-circulating water baths are suitable for incubating small volumes of samples, as they do not have the pumping action of a circulating water bath, which can cause samples to be displaced.
4. Energy efficient: Non-circulating water baths do not have a circulating pump, making them more energy efficient compared to circulating water baths.
5. Gentle mixing: The lack of a circulating pump in a non-circulating water bath means that the samples are not subjected to any pumping action, which can be beneficial for certain types of samples that require gentle mixing or stirring.

4. Water-jacketed heating block

A water-jacketed heating block is a type of water bath that consists of a heating element surrounded by a water-filled jacket. Materials are placed in a container, such as a test tube or flask, and the container is placed in the heating block. The water in the jacket helps to evenly distribute the heat to the materials.

Applications of Water-jacketed heating block

• A water bath is laboratory equipment consisting of a heated water-filled container. It is utilised to incubate water samples at a steady temperature for an extended period of time.

Advantages of Water-jacketed heating block

1. Precise temperature control: The water-jacketed heating block allows for precise temperature control, as the temperature of the heating block can be accurately regulated using a temperature control system.
2. Uniform heating: The water jacket surrounding the heating block helps to distribute the heat evenly, resulting in uniform heating of the samples.
3. Gentle heating: The water jacket helps to gently heat the samples, reducing the risk of overheating or thermal shock.
4. Efficient heat transfer: The water jacket helps to efficiently transfer heat to the samples, resulting in faster heating and shorter incubation times.
5. Versatility: Water-jacketed heating block water baths can be used for a wide range of applications, including incubating cell cultures, enzymes, bacteria, and tissue cultures. They can also be used for maintaining the temperature of samples during experiments or reactions.

5. Immersion water bath

An immersion water bath is a type of laboratory water bath that is used to incubate samples in a water bath. It consists of a container filled with water, which is heated to a desired temperature using a heating element. The samples to be incubated are placed in tubes or containers and immersed in the water bath. The temperature of the water bath is typically controlled using a temperature control system, and the water is stirred using a stirrer to ensure a uniform temperature throughout the bath. Immersion water baths are commonly used for incubating small volumes of samples at a constant temperature, such as enzymes, bacteria, and tissue cultures. They are also useful for maintaining the temperature of samples during experiments or reactions.

An immersion water bath consists of a container filled with water that is heated using a heating element. Materials are placed directly into the water to be heated.

Applications of Immersion water bath

• These are utilised to incubate water samples at a steady temperature for extended periods of time. They are useful for flammable liquids and biological substances that should not be exposed to direct heat.

Advantages of Immersion water bath

1. Simplicity: Immersion water baths are simple in design and easy to use, making them suitable for a wide range of applications.
2. Low cost: Immersion water baths are typically less expensive than other types of water baths, as they do not have the added complexity of a circulating pump or shaking mechanism.
3. Suitable for small volumes: Immersion water baths are suitable for incubating small volumes of samples, as they do not have the pumping action of a circulating water bath or the shaking action of a shaking water bath, which can cause samples to be displaced.
4. Gentle heating: Immersion water baths provide gentle heating of the samples, reducing the risk of overheating or thermal shock.
5. Efficient heat transfer: The direct contact between the samples and the water in an immersion water bath helps to efficiently transfer heat to the samples, resulting in faster heating and shorter incubation times.
6. Versatility: Immersion water baths can be used for a wide range of applications, including incubating cell cultures, enzymes, bacteria, and tissue cultures. They can also be used for maintaining the temperature of samples during experiments or reactions.

6. Polycarbonate Water Bath

Polycarbonate water baths are laboratory water baths made from polycarbonate, a type of plastic that is known for its strength and durability. They are often used in laboratories due to their lightweight and break-resistant properties. Polycarbonate water baths are available in a range of sizes and styles to accommodate different sizes and types of samples. They are commonly used for incubating samples at a constant temperature, such as enzymes, bacteria, and tissue cultures. Polycarbonate water baths are also resistant to most acids and bases, making them suitable for use in a variety of applications. Some polycarbonate water baths also have built-in temperature controls and stirrers to help maintain a uniform temperature and mix the water.

Applications of Polycarbonate Water Bath

• Designed for a range of applications, including the heating of liquids, samples, emulsions, creams, and consumables in test tubes, containers, bottles, Erlenmeyers, bags, and utensils.

Advantages of Polycarbonate Water Bath

1. Lightweight: Polycarbonate water baths are lightweight and easy to handle, making them suitable for use in a variety of settings.
2. Durability: Polycarbonate is a strong and durable material, making polycarbonate water baths resistant to breakage and wear and tear.
3. Chemical resistance: Polycarbonate is resistant to most acids and bases, making polycarbonate water baths suitable for use in a wide range of applications.
4. Transparency: Polycarbonate is a transparent material, which can be useful for monitoring the samples being incubated in the water bath.
5. Ease of cleaning: Polycarbonate water baths are easy to clean and maintain, as they do not rust or corrode.
6. Versatility: Polycarbonate water baths can be used for a wide range of applications, including incubating cell cultures, enzymes, bacteria, and tissue cultures. They can also be used for maintaining the temperature of samples during experiments or reactions.

6. Other Types of Water Bath

1. Water baths with a fixed water volume: These water baths have a fixed volume of water that cannot be adjusted. They are suitable for incubating small samples.
2. Water baths with adjustable water volume: These water baths have a water volume that can be adjusted to accommodate different sizes of samples.
3. Low-temperature water baths: These water baths are designed to maintain low temperatures, usually below 25°C. They are commonly used for incubating samples that require cool temperatures, such as enzymes and bacteria.
4. High-temperature water baths: These water baths are designed to maintain high temperatures, usually above 50°C. They are commonly used for incubating samples that require higher temperatures, such as tissue cultures.

Operating Procedure of a Laboratory Water Bath

1. Open the container’s lid and fill it with water up to three-quarters of the bath’s height, then close it.
2. Turn ON both the mains and the instrument.
3. Red and yellow light will reflect off of the mains and the heaters, respectively.
4. Then, with the use of a temperature control knob, set the temperature and allow it to increase to the desired level.
5. After attaining the required temperature with the aid of a thermometer, open the container’s lid and place the sample inside for the required time.
6. Upon completion, remove the sample and turn off the instrument and main power.
7. Finally, pour all water from the container through the valve and dry the instrument before replacing the lid.

What is Analog water bath?

An analog water bath is a type of laboratory water bath that uses an analog temperature control system. An analog temperature control system uses a dial or knob to adjust the temperature of the water bath. The user sets the desired temperature by turning the dial or knob to the appropriate setting, and the temperature of the water bath is then maintained at that level.

Analog water baths are typically less expensive than digital water baths, as they do not have the added complexity of a digital temperature control system. However, they are not as precise as digital water baths and may not be suitable for incubating samples that require precise temperature control. Analog water baths are also less user-friendly than digital water baths, as the user must manually adjust the temperature using the dial or knob.

Principle of Analog water bath

When power is supplied to the device, the mains indicator will illuminate. The current will then proceed to the thermostat. Current will flow through the water immersion heater from the thermostat.

When the water temperature is below the set point, the thermostat will enable current to flow through the heating element. Consequently, the water’s temperature will begin to rise. Once the water reaches the desired temperature, the thermostat will shut off. Consequently, no current will travel via the heating rod. The water temperature then begins to decrease. Additionally, the heating indicator will cease to light.

What is Digital Water Bath?

A digital water bath is a type of laboratory water bath that uses a digital temperature control system. A digital temperature control system allows the user to set the desired temperature using a digital display and buttons, rather than a dial or knob. The temperature of the water bath is then maintained at that level using a heating element and temperature sensor.

Digital water baths are more precise and user-friendly than analog water baths, as the user can set the temperature to a specific value using the digital display and buttons. They are also easier to read and monitor, as the temperature is displayed digitally rather than on a dial or knob. However, digital water baths are typically more expensive than analog water baths, as they have the added complexity of a digital temperature control system.

*A digital water bath is constructed similarly to an analogue water bath. The only difference is that a solid-state relay and PID temperature controller replace the thermostat. Similarly, there is a temperature sensor present.

Principle of Digital Water Bath

The mechanism is nearly identical to that of an analogue water bath. Here, the PID controller and the solid-state relay (SSR) serve as water immersion heater controllers. When the water temperature falls below the specified point, the controller will send a specific DC voltage to the relay. The relay will then be engaged, causing AC current to flow to the heating rod. Consequently, the heater begins heating the water.

When the actual water temperature approaches the preset value, the PID controller will constantly activate and deactivate the relay. Thus, the heating rod will be continually ON/OFF. Therefore, by regulating the duration of the ON and OFF stages, the water bath helps to maintain a nearly correct result with a variance of no more than 1°C.

The resistance temperature detector (RTD) or PT100 sensor measures the water’s temperature. The temperature is then converted to a resistance value and sent to the controller. This incoming signal will be compared to the predetermined value by the controller.

Analog Water Bath Vs Digital Water Bath

Analog water baths and digital water baths are both types of laboratory water baths that are used to incubate samples at a constant temperature. Some differences between analog water baths and digital water baths include:

1. Temperature control system: Analog water baths use an analog temperature control system, which uses a dial or knob to adjust the temperature of the water bath. Digital water baths use a digital temperature control system, which allows the user to set the temperature using a digital display and buttons.
2. Precision: Digital water baths are more precise than analog water baths, as they allow the user to set the temperature to a specific value using the digital display and buttons. Analog water baths are less precise, as the user must manually adjust the temperature using a dial or knob.
3. User-friendliness: Digital water baths are generally more user-friendly than analog water baths, as they have a digital display and buttons that are easy to read and use. Analog water baths require the user to manually adjust the temperature using a dial or knob.
4. Cost: Digital water baths are typically more expensive than analog water baths, as they have the added complexity of a digital temperature control system.

What is the temperature range of water bath used in laboratory?

The temperature range of a water bath depends on the type of water bath and the specific model. Most water baths are able to maintain temperatures within a certain range, usually between 4°C and 99°C. However, some water baths may be able to maintain temperatures outside of this range, either higher or lower.

It is important to choose a water bath with a temperature range that is suitable for the samples being incubated. For example, if the samples require a temperature of 37°C, a water bath with a temperature range of 4°C to 99°C would be suitable. If the samples require a lower or higher temperature, a water bath with a wider temperature range may be necessary.

It is also important to consider the precision of the water bath when selecting the appropriate temperature range. Some water baths are more precise than others and may be able to maintain a specific temperature more accurately. This can be important for incubating samples that require precise temperature control.

What is Oil bath and sand bath?

Oil soak

• In place of water, a high-conduction oil (such as soybean or cottonseed oil) is utilised.
• It can maintain temperatures up to 300 degrees Celsius.
• It offers more consistent heat than water and sand baths.

Sand soak

• Yellow sand is used in place of water, however its conductivity is lower than that of a bath of water and oil.
• The heating rod is constructed from aluminium.
• A portion of the reaction vessel is covered with sand. The sand transfers heat from the plate to the reaction vessel walls.

Advantages of laboratory Water Bath

1. Constant temperature: Water baths are able to maintain a constant temperature, making them suitable for incubating samples that require precise temperature control. Even if numerous samples are heated at the same time, there is a low probability of temperature fluctuations since water baths may retain a substantial amount of heat.
2. Gentle heating: Water baths provide gentle heating of the samples, reducing the risk of overheating or thermal shock.
3. Efficient heat transfer: The direct contact between the samples and the water in a water bath helps to efficiently transfer heat to the samples, resulting in faster heating and shorter incubation times.
4. Versatility: Water baths can be used for a wide range of applications, including incubating cell cultures, enzymes, bacteria, and tissue cultures. They can also be used for maintaining the temperature of samples during experiments or reactions.
5. Ease of use: Water baths are relatively easy to use and can be set up and operated with minimal training. The greater surface area of water baths enables samples to be heated more quickly.
6. Ease of cleaning: Water baths are easy to clean and maintain, as they do not have complex moving parts that can be damaged or require maintenance.

Limitation of laboratory Water Bath

1. Limited temperature range: Water baths are typically only able to maintain temperatures within a certain range, usually between 4°C and 99°C. They may not be suitable for incubating samples that require temperatures outside of this range.
2. Risk of evaporation: Water baths are open systems, which means that there is a risk of evaporation over time. This can lead to a loss of water and a decrease in the temperature of the water bath.
3. Limited sample capacity: Water baths have a limited capacity for samples, depending on the size of the water bath and the size of the tubes or containers holding the samples. This can be a limitation for incubating large volumes of samples.
4. Risk of contamination: Water baths are open systems, which means that there is a risk of contamination if the samples are not properly sealed or handled.
5. Maintenance requirements: Water baths require regular maintenance to ensure that they are functioning properly and maintaining the desired temperature. This may involve cleaning the bath, replacing the heating element, or replacing the temperature control system.

Application of laboratory Water Bath

Laboratory water baths are widely used in research and industrial laboratories for incubating samples at a constant temperature. Some common applications of water baths include:

1. Incubating cell cultures: Water baths are commonly used for incubating cell cultures at a constant temperature, such as bacteria, fungi, and cells from higher organisms.
2. Enzyme reactions: Water baths are often used to maintain the temperature of enzyme reactions, as enzymes have optimal activity at specific temperatures.
3. Bacterial cultures: Water baths are used to incubate bacterial cultures at a constant temperature, allowing the bacteria to grow and multiply.
4. Tissue cultures: Water baths are used to incubate tissue cultures at a constant temperature, allowing the tissues to grow and differentiate.
5. Protein crystallization: Water baths are used to maintain the temperature of protein crystallization experiments, as proteins have optimal crystallization conditions at specific temperatures.
6. Chemical reactions: Water baths are used to maintain the temperature of chemical reactions, as many reactions have optimal conditions at specific temperatures.
7. Industrial processes: Water baths are used in industrial settings to maintain the temperature of various processes, such as chemical reactions, heating, and cooling.

Precautions

• Utilize with care.
• With moisture-sensitive or pyrophoric reactions, it is not suggested to utilise a water bath.
• Never heat a bath fluid past the flash point.
• The water level should be monitored frequently and filled with only distilled water.
• This is essential to prevent the deposition of salts on the heater.
• Add disinfectants to prevent the growth of microorganisms.
• Once a week for half an hour, raise the temperature to 90 °C or greater for the aim of disinfection.
• Markers are typically easily removed from water baths. Use water resistant ones.
• If the application involves liquids that emit vapours, it is recommended to operate the water bath inside a fume hood or in an area with enough ventilation.
• The lid is sealed to avoid evaporation and aid in achieving high temperatures.
• Establish on a stable surface away from combustible materials.

Also Read:

• The Complement Pathway, Activation, Functions, and Deficiencies.

Reference

• https://www.tec2med.com/water-bath-working-handling-maintenance/
• https://www.labkafe.com/blog/how-to-use-water-bath-in-laboratory-working-principal-types-maintenance#:~:text=Working%20principle%20of%20water%20bath%3A%20The%20sensor%20transfer%20water%20temperature,maintain%20water%20in%20constant%20temperature.
• https://www.stericox.com/water-bath/
• https://www.labrotovap.com/working-principle-of-water-bath/
• http://www.lanphan.com/lab-instruments/working-principle-of-water-bath-605.html
• https://www.slideshare.net/TayyabTariq8/water-bath-instrument
• https://www.slideshare.net/goldenalzaidy/pdf-water-bath-laboratory-applications
• https://en.wikipedia.org/wiki/Laboratory_water_bath