Dilution is a chemical process that involves reducing the concentration of a substance in a solution. This is achieved by adding more solvent, the component that does the dissolving, without adding any more of the dissolved substance, called the solute. The resulting solution has a lower concentration than the initial one because the same amount of solute is dispersed throughout a larger volume. This procedure is used across various scientific and commercial fields to achieve a reduction in strength.
Understanding Concentration and the Physical Process
A solution is a uniform mixture composed of a solute (the substance being dissolved) and a solvent (the substance doing the dissolving, such as water). The concentration of this solution measures the amount of solute present relative to the total volume.
A highly concentrated solution, often called a stock solution, holds a large amount of solute particles packed into a small volume. When dilution is performed, additional solvent is introduced into this stock solution. The total number of solute particles remains exactly the same because no solute is removed or added during the process.
The added solvent increases the overall volume, causing the existing solute particles to spread farther apart. This increase in the ratio of solvent to solute lowers the concentration of the final solution. A sample of any given volume now contains fewer solute particles than the same volume of the original stock solution.
Calculating Dilution Factors
Dilution is a mathematically precise process that relies on the principle of conservation of mass. The most common mathematical tool used to quantify this change is the dilution equation: \(C_1V_1 = C_2V_2\). In this formula, \(C_1\) and \(V_1\) represent the initial concentration and volume of the stock solution.
\(C_2\) and \(V_2\) represent the final concentration and the total final volume of the diluted solution. Since the product of concentration and volume (\(C \times V\)) represents the total amount of solute, the formula states that the amount of solute before dilution equals the amount after dilution. This relationship allows scientists to calculate any unknown variable if the other three values are known.
The Dilution Factor (DF) is another way to express the magnitude of the dilution, often presented as a ratio. A 1:10 dilution means one unit of the original solution is combined with nine units of solvent to create ten total units. This factor directly relates the volume of the stock solution to the final volume, indicating the factor by which the concentration has been reduced.
Practical Uses of Dilution
Dilution is a technique used across various fields, extending into everyday products and medical care. In household settings, many cleaning products are sold as concentrated formulas that must be diluted with water before use. This practice reduces transportation costs and packaging waste by allowing a smaller volume of concentrated product to yield many liters of ready-to-use cleaner.
In medicine, dilution is routinely performed to prepare patient-specific dosages from concentrated medications. A pharmacist or nurse may need to dilute an injectable drug or a stock solution for an intravenous (IV) drip to achieve the precise concentration required for a patient. This ensures the patient receives the correct therapeutic dose.
Laboratory science relies on controlled dilutions for accurate testing and analysis. Techniques like serial dilution involve a step-wise process necessary in microbiology to accurately count microorganisms. Analytical chemists also use dilution to bring samples with unknown concentrations into the measurable range of sensitive instruments.