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Constant Pressure Calorimetry03:02

Constant Pressure Calorimetry

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Calorimetry is a technique used to measure the amount of heat involved in a chemical or physical process or to measure the heat transferred to or from a substance. The heat is exchanged with a calibrated and insulated device called the calorimeter. Calorimetry experiments are based on the assumption that there is no heat exchange between the insulated calorimeter and the external environment. The well-insulated calorimeters prevent the transfer of heat between the calorimeter and its external...
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Calorimetry01:19

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When objects at different temperatures are placed in contact with each other but isolated from everything else, they attain thermal equilibrium. A container that prevents heat transfer in or out is called a calorimeter, and the use of a calorimeter to make measurements is called calorimetry. Generally, these measurements involve heat or specific heat capacity. The term "calorimetry problem" is used for any problem where the specified objects are thermally isolated from their...
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Constant Volume Calorimetry02:41

Constant Volume Calorimetry

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Calorimeters are useful to determine the heat released or absorbed by a chemical reaction. Coffee cup calorimeters are designed to operate at constant (atmospheric) pressure and are convenient to measure heat flow (or enthalpy change) accompanying processes that occur in solution at constant pressure. A different type of calorimeter that operates at constant volume, colloquially known as a bomb calorimeter, is used to measure the energy produced by reactions that yield large amounts of heat and...
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Enthalpy02:59

Enthalpy

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Chemists ordinarily use a property known as enthalpy (H) to describe the thermodynamics of chemical and physical processes. Enthalpy is defined as the sum of a system’s internal energy (E) and the mathematical product of its pressure (P) and volume (V):
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Quantifying Heat02:46

Quantifying Heat

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Thermal Energy Microscopically, thermal energy is the kinetic energy associated with the random motion of atoms and molecules. Temperature is a quantitative measure of “hot” or “cold”, which depends on the amount of thermal energy. When the atoms and molecules in an object are moving or vibrating quickly, they have a higher average kinetic energy (KE) (or higher thermal energy), and the object is perceived as “hot”, or it is described as being at a higher temperature. When the...
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Specific Heat01:16

Specific Heat

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The specific heat capacity of a substance refers to the energy required to increase the temperature of one gram of that substance by one degree Celcius. Specific heat capacity is often represented in calories (cal), grams (g), and degrees Celsius (oC), but can also be expressed in joules (J), kilograms (kg), and Kelvin (K), among other units.
For example, increasing the temperature of one gram of water by 1°C requires one calorie of heat energy and can be written as 1 cal/g-°C, or...
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Related Experiment Video

Updated: Mar 12, 2026

Pool-Boiling Heat-Transfer Enhancement on Cylindrical Surfaces with Hybrid Wettable Patterns
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Water Calorimetry: The Heat Defect.

Norman V Klassen1, Carl K Ross1

  • 1Ionizing Radiation Standards, Institute for National Measurement Standards, National Research Council Canada, Ottawa K1A 0R6 Canada.

Journal of Research of the National Institute of Standards and Technology
|January 1, 1997
PubMed
Summary

This study explored how different gas mixtures in water affect the performance of water calorimeters used to measure absorbed radiation dose. Researchers found that water saturated with a 50% hydrogen and 50% oxygen mixture works well if it is stirred and has a gas space. H2-saturated water is also viable but needs to avoid oxygen contamination. Pure water may require a priming dose to remove impurities. The study used simulations and experiments to compare various water types. The results help clarify the best conditions for accurate water calorimetry. These findings could improve the reliability of radiation dose measurements in medical and industrial applications.

Keywords:
absorbed dose to waterdosimetryionizing radiationwater calorimetryradiation dosimetrywater calorimetergas-saturated waterH2O2 production

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Area of Science:

  • Radiation metrology
  • Thermal physics in analytical chemistry
  • Water-based dosimetry

Background:

Water calorimetry is a key method for measuring absorbed dose in ionizing radiation. However, the presence of gases in water can alter the accuracy of these measurements. Prior research has shown that gas mixtures can influence radiolysis products and heat transfer. No prior work had resolved the specific impact of varying hydrogen and oxygen ratios in gas-saturated water. This gap motivated the current investigation into how different gas compositions affect calorimeter performance. Researchers had already noted anomalies in calorimetry when using gas-saturated water. The behavior of water saturated with hydrogen and oxygen mixtures remained unclear. This study aimed to clarify the role of gas composition in the heat defect. Understanding this could improve the reliability of water calorimeters in radiation dosimetry.

Purpose Of The Study:

The study aimed to investigate the heat defect in water calorimeters using different gas-saturated water mixtures. The researchers wanted to determine how hydrogen and oxygen ratios affect calorimeter behavior. They focused on mixtures where the amount-of-substance of H2 and O2 was not 50%. The goal was to understand the underlying radiolysis processes. This could help optimize water calorimeters for more accurate dose measurements. The study also examined other aqueous solutions used in calorimetry. The researchers compared experimental results with computer simulations. Their findings could guide the selection of appropriate water conditions for calorimetry.

Main Methods:

The team used computer simulations to model the radiolysis of water under various gas conditions. They tested mixtures with differing proportions of hydrogen and oxygen. Simulations were run for pure water, air-saturated water, and H2-saturated water. The production of H2O2 was measured and compared with simulation results. The researchers assessed how gas composition affects heat transfer in calorimeters. They evaluated the role of OH radicals and scavengers in the process. The simulations helped explain the observed anomalies in calorimeter behavior. The study combined theoretical modeling with experimental validation.

Main Results:

The simulations showed that gas mixtures with non-50% H2 and O2 ratios caused the observed calorimeter anomalies. Water with 50% H2 and 50% O2 was found suitable if stirred and in contact with a gas space. H2-saturated water did not need a gas space but required protection from O2 contamination. Pure water lacked OH radical scavengers, which could affect impurity removal. Some pure water might need a priming dose to remove reactive impurities. The study found that air-saturated water posed experimental and theoretical challenges. O2-saturated water also introduced complications in calorimeter design. The results suggest that gas composition significantly influences calorimeter accuracy.

Conclusions:

The study supports the use of 50% H2 and 50% O2 mixtures in water calorimeters under specific conditions. Stirring and gas space contact are necessary for this setup. H2-saturated water is viable but requires careful handling to avoid O2 contamination. Pure water may need a priming dose depending on its purity. The absence of OH scavengers in pure water affects impurity removal. Air and O2-saturated water present unresolved issues in calorimetry. The findings help clarify the role of gas composition in water calorimeters. These conclusions align with the observed calorimeter behavior and simulations.

A 50% H2 and 50% O2 mixture is suitable if the water is stirred and in contact with a gas space.

H2-saturated water does not require a gas space but must be protected from O2 contamination.

The lack of scavengers in pure water may require a priming dose to remove reactive impurities.

H2O2 production was measured in various aqueous solutions and compared to computer simulations.

The heat defect refers to anomalous behavior in calorimeters using gas-saturated water mixtures.

Air-saturated water introduces experimental and theoretical problems in water calorimetry.