Final answer:
The LD50, or median lethal dose, is the dose of a chemical that is lethal to 50% of a test animal population, and is used to express and compare the toxicity of different substances.
Step-by-step explanation:
The LD50, which stands for median lethal dose, is a measure used to express the toxicity of a substance. It is defined as the dose of a chemical that is lethal to 50% of a test animal population after a specified test duration. When determining the LD50, animals such as rats or mice are typically used for experiments, and the dosing is calculated relative to the animal's size, usually in milligrams of chemical per kilogram of body weight (mg/kg).
The determination of the LD50 requires precise controlled experiments where different groups of animals are administered varying doses of a toxin, and the percentage of animals that die after exposure is recorded. This information is then plotted on a log-dose response curve to determine the dose that will result in 50% mortality. It is essential when comparing the toxicity of different chemicals as it provides a standardized method for such comparisons.