What Is a Calorimeter & How Is It Used In A Lab?

What Is a Calorimeter & How Is It Used In A Lab?

The history of the calorimeter dates back to the early 19th century. The concept of measuring heat exchange during chemical reactions can be traced to the work of Antoine Lavoisier, a prominent French chemist. In the late 18th century, Lavoisier conducted experiments that led to the development of the concept of heat as a form of energy.

The first practical calorimeter was constructed by Count Rumford, an American-born British scientist, in the late 18th century. Rumford's device, known as the "Rumford calorimeter," was used to study the heat generated by the boring of cannons. His experiments led to the understanding that heat was not a substance but a form of energy.

In the early 19th century, the French chemist Pierre-Joseph Dulong and the French physicist Alexis Thérèse Petit developed a type of calorimeter that allowed for the determination of specific heat capacities of materials. This marked a significant advancement in the field of thermodynamics.

One of the most renowned developments in calorimetry came in the mid-19th century with the work of James Prescott Joule, an English physicist. Joule's experiments on the mechanical equivalent of heat established the relationship between mechanical work and heat energy. His work provided crucial evidence for the conservation of energy and laid the foundation for modern thermodynamics.

Throughout the 19th and early 20th centuries, various types of calorimeters were developed, each suited for specific applications. These ranged from bomb calorimeters used to measure the heat of combustion to adiabatic calorimeters used for studying reactions in a controlled environment.

Advancements in technology and materials over the years have led to the development of more sophisticated and precise calorimeters. These instruments are now crucial in fields like chemistry, physics, biology, and material science, enabling researchers to gain deeper insights into the energy changes associated with chemical reactions and physical processes. If you’re looking to outfit your lab with a variety of analytical instruments, a calorimeter may be something you add to your list.

In the chemical industry, they are used for quality control, and in biological studies, they are used for metabolic rate examination. In this post, we'll explore what a calorimeter does, how it works, and more.

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What Does A Calorimeter Do?

A calorimeter is an instrument designed to quantify changes in heat. Typically, it comprises a metal container with water above a combustion chamber. A thermometer gauges the heat change within the water. While basic versions can be fashioned using household items like coffee or styrofoam cups, they aren't as precise as professional lab-grade equipment. More sophisticated calorimeters exist, offering enhanced accuracy and capabilities.

When energy is gained or lost, the liquid's temperature shifts. The calorimeter records both the mass of the liquid and its temperature alteration, enabling the determination of energy changes. It's important to note that calorimetry differs from thermal analysis, which assesses material properties across different temperatures. This distinction underscores the specialized role of each instrument in scientific experimentation.

How Does It Work?

Calorimeters, composed of inner and outer vessels separated by insulating air, control heat exchange with the surroundings. Lab-grade models incorporate a fiber ring for inner vessel centering, while a thermometer monitors the liquid's temperature. A stirrer ensures even heat distribution.

During exothermic reactions, heat release raises the solution's temperature; conversely, endothermic reactions absorb thermal energy, leading to a temperature drop. When energy exchange ceases, thermal equilibrium is reached. Accounting for temperature changes, solution mass, and specific heat enables precise heat quantification.

The temperature shift aids in determining the enthalpy change per mole of substance A in reactions. Calculated using q = Cv(Tf – Ti ), Q signifies heat in joules, Cv denotes calorimeter capacity (j/K), Tf is the final temperature, and Ti is the initial temperature. This formula is pivotal in accurately assessing energy changes during chemical reactions.

Calorimeters operate on the principle of energy conservation, maintaining a constant total energy in a closed system. The inner vessel, housing reactants, is enclosed by an insulating outer vessel. A fiber ring, made of insulating material, centers the inner vessel, ensuring efficient containment of reaction-generated or absorbed heat.

A stirrer guarantees uniform heat distribution within the inner container, facilitating precise temperature change measurement. The enthalpy change per mole of substance A is a crucial parameter in chemical thermodynamics, offering insights into energy transformations during reactions. By measuring initial and final temperatures and considering calorimeter heat capacity, scientists can calculate this vital value, enhancing understanding of underlying chemical processes.

Types of Calorimeters Used in the Lab

  • Adiabatic: Adiabatic calorimeters are used to study runaway reactions. With this type, some heat is always lost. As a result, a correction factor is applied to compensate for that heat loss.
  • Reaction: With this type, chemical processes occur within a closed, insulated container. The heat flow vs. time is measured to determine the reaction heat. It’s used to find the maximum heat a reaction releases, or for reactions that need to run at a constant temperature.
  • Heat flow: With this type, a heating/cooling jacket controls the temperature of the physical process or the temperature of the jacket. The heat of the reaction is determined by measuring the temperature difference between the heat transfer fluid and the process fluid. It is necessary to know the fill volumes, specific heat, and heat transfer coefficient before a correct answer can be found.
  • Heat balance: With this type of calorimeter, the heating/cooling jacket controls the temperature of the process. Heat is measured by monitoring the heat that’s gained or lost by the transfer fluid.
  • Power compensation: This uses a heater added to the vessel so it maintains a constant temperature. The energy for the heater can be adjusted as the reaction requires. The calorimetry signal comes from electrical power.
  • Constant flux: This comes from heat balance calorimetry, but has a specialized control to maintain a constant flow of heat across the container wall.
  • Bomb Calorimeter: Also known as a constant-volume calorimeter, this is built to withstand the pressure that builds up as a result of a reaction as air heats in the reaction vessel. The change in water temperature is used to calculate the heat of combustion.
  • Calvet-type: This type uses a 3D fluxmeter sensor that’s made of a series of thermocouple rings. It is well-suited for larger sample size because it allows for a larger reaction container size, without affecting the measurement accuracy.
  • Constant-pressure: The coffee cup calorimeter you can make at home is an example of a constant-pressure calorimeter. It measures the thermodynamic change in a solution, under constant pressure.
  • Differential Scanning: With DSC, there are typically two pans, one sample pan, and one reference pan. The sample pan contains the sample while the reference pan remains empty. Each pan is heated separately at a specific rate, and this rate is maintained throughout the experiment. A computer system ensures that each pan heats up at the same rate, however, so that a measurement can be taken. The heater underneath the sample pan has to work harder than the empty reference pan, meaning it puts out more heat. The difference in the amount of heat put out is how a measurement is made.
  • Isothermal titration: In this type, the heat of reaction is used to follow a titration experiment. It’s possible to determine the midpoint of the reaction and its enthalpy and its binding affinity. It’s helpful in the pharmaceutical industry to classify potential drug candidates.

How Much do Calorimeters Cost?

The cost of a calorimeter can vary widely depending on factors such as its type and size. For a brand new calorimeter, you can anticipate spending anywhere between approximately $15,000 to $40,000. This price range reflects the diversity of calorimeter models available in the market, which cater to different research needs and specifications. Larger and more advanced calorimeters typically fall towards the higher end of this range due to their increased capacity and capabilities.

If you are working within a budget, it's worth considering used models, which can offer significant cost savings. You can find pre-owned calorimeters for as little as $9,000. However, when purchasing a used instrument, it's crucial to ensure that it has been well-maintained and calibrated to ensure accurate and reliable measurements.

Ultimately, the choice of a calorimeter should be based on your specific research requirements, available budget, and the level of precision and capabilities needed for your experiments. Consulting with experts or colleagues in your field can also provide valuable insights into which type and model of calorimeter would best suit your needs.

Leasing vs. Buying Calorimeter

Leasing a calorimeter can be an excellent strategy for laboratories, especially when there's a need for multiple pieces of specialized equipment like TOC analyzers, elemental analyzers, or mass spectrometers. Acquiring such equipment outright often requires a substantial upfront investment.

By opting to lease, labs can effectively allocate their startup funds. Instead of a significant initial outlay, they make manageable monthly payments, which can be particularly advantageous for labs working within budget constraints. This approach not only eases the financial burden but also allows for the acquisition of all necessary equipment without compromising on quality.

Furthermore, one of the significant benefits of leasing is the inclusion of maintenance and repair costs in the lease agreement. This means that any unforeseen maintenance or repairs that may be required during the lease period are covered, providing labs with peace of mind and budget predictability.

In essence, leasing enables labs to access state-of-the-art equipment without depleting their initial capital. This approach not only fosters a more cost-effective procurement process but also ensures that labs have the necessary tools to conduct their research efficiently and accurately.

If your lab is considering leasing equipment like a calorimeter or other specialized lab instruments, don't hesitate to reach out. We can provide further information on the benefits of leasing, as well as guide you through the process to best suit your specific needs and requirements.