What is the determination of the osmotic pressure of a solution based on the relative number of solute particles in 1 kg of the solution?

The determination of osmotic pressure in relation to the relative number of solute particles per kilogram of solvent is best described by the term "osmolality." Osmolality specifically refers to the concentration of solute particles in a solution, measured in osmoles per kilogram of solvent. This is important in veterinary pharmacology as it helps understand the behavior of substances in biological systems, particularly in relation to fluid movements across cell membranes.

Osmolarity, while similar, refers to the concentration of solute particles in a given volume of solution rather than per kilogram of solvent, which can lead to different values depending on temperature and the density of the solution. Concentration is a more general term that encompasses any measure of the amount of solute in a given amount of solvent or solution but does not specifically address the impact of the number of particles on osmotic pressure. Dilution describes the process of reducing the concentration of a solute in a solution but does not pertain to the measurement of osmotic pressure or the evaluation of solute particles directly. Thus, osmolality is the most accurate term for the definition provided in the question.