= Heat defect
{disambiguate=calorimetry}
{title2=$k_{\mathrm{HD}}=(E_a-E_h)/E_a$}
= Heat defect
{synonym}
The \b[heat defect] in <water calorimetry> measures the fraction of absorbed energy that does not appear as heat because of radiation-induced chemical changes. Writing absorbed energy as $E_a$ and the energy appearing as heat as $E_h$, the convention used by <Norman V. Klassen> and <Carl K. Ross> is
$$
k_{\mathrm{HD}}=\frac{E_a-E_h}{E_a}.
$$
A positive value means less heat than the absorbed-energy equivalent; a negative value means the chemical response adds heat.<Water Calorimetry: The Heat Defect by Norman V. Klassen and Carl K. Ross>[Printed p.63, Eqs1–2 and accompanying definition.]{ref}
If other thermal corrections are treated separately, the <absorbed dose> is
$$
D_w=\frac{c_w\Delta T}{1-k_{\mathrm{HD}}}.
$$
An illustrative $k_{\mathrm{HD}}=0.02$ means that $c_w\Delta T$ represents 98% of the dose, so the chemical correction multiplies that thermal estimate by $1/0.98$. The example fixes a sign convention; it is not a measured universal value for water.
The motivating evidence included variations with dissolved gases and comparison of <radiolysis> calculations with chemical measurements of <hydrogen peroxide>. Those tests address chemical energy accounting. An external heat leak or a drifting thermometer can also alter a temperature reading, but belongs to a different correction mechanism.<Water Calorimetry: The Heat Defect by Norman V. Klassen and Carl K. Ross>[Abstract and Introduction: radiolysis model and independently measured chemical product.]{ref}
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