Distilled water that has been stabilized, buffered, and aerated. Dilution is usually used in BOD tests for the purposes of removing the concentration of solute from a solution by increasing the amount of solvent in the solution. Solvent and solute make up the solution, which makes pure water more categorized as a substance rather than pure water since it can not be diluted. Dilute solutions generally consist of only a few solute dissolved in a specific amount of solvent. In layman terms, solvent molecules only have a minimal amount of solute in between them. But it is important to understand that water does not always contain solvent. Good examples of real solvents are turpentine and alcoholic beverages.