Dilution is the process of decreasing the concentration of a solute in a solution, typically by adding more solvent, which reduces the amount of the original substance per unit of total volume. The technique is fundamental across various scientific and domestic fields when a starting material, known as the stock solution, is too concentrated for its intended application. The 1:10 dilution is one of the most common and standardized methods used for creating solutions with a lower, more manageable strength.
Decoding the 1:10 Ratio
The 1:10 ratio represents a dilution factor of 10, meaning the final solution will have one-tenth the concentration of the original stock solution. This ratio is interpreted as one part of the stock solution mixed to achieve a final total volume of ten parts. Therefore, to make a 1:10 dilution, one volume of the concentrated stock solution is combined with nine volumes of the solvent (or diluent) to reach the final total volume. For instance, combining 1 milliliter (mL) of a stock solution with 9 mL of water yields 10 mL of the 1:10 diluted solution.
Essential Equipment and Materials
Accurately executing a 1:10 dilution requires the correct concentrated stock solution, the appropriate solvent (often distilled or deionized water), and precise measuring tools. In laboratory settings, volumetric glassware is preferred because it is specifically calibrated to contain a highly accurate, single volume. Volumetric flasks are the best choice for preparing the final volume, as they have a single mark on the neck indicating the exact volume they are meant to contain. For transferring the stock solution, a volumetric pipette is used, offering superior precision compared to a graduated cylinder or a simple dropper. All equipment must be clean and dry to prevent contamination or alteration of the concentration.
Step-by-Step Procedure for Accurate Dilution
Before mixing, calculate the precise volumes of stock solution and solvent needed based on the desired final volume. For example, preparing 100 mL of a 1:10 dilution requires measuring 10 mL of the stock solution and adding 90 mL of solvent to reach the 100 mL mark. Safety measures, including wearing personal protective equipment such as chemical splash goggles and gloves, must be taken, especially when handling concentrated or corrosive materials.
The measured volume of the stock solution is carefully added to a clean volumetric flask; the stock solution must be added first before the diluent. The flask is then filled partway—approximately two-thirds full—with the solvent to begin the dilution and initial mixing. If the stock solution is a concentrated acid or base, the correct technique involves adding the concentrated substance slowly to the larger volume of water, never the reverse, to safely manage the heat generated.
After initial mixing by gentle swirling, add the solvent until the liquid level approaches the calibration mark on the flask’s neck. The final few drops are added carefully, often with a dropper or wash bottle, until the bottom of the liquid’s meniscus aligns perfectly with the engraved mark when viewed at eye level. This process, known as “diluting to volume,” ensures the final volume is exactly ten parts. Once diluted, the flask is stoppered tightly and inverted repeatedly, typically ten to fifteen times, to ensure the stock solution is thoroughly and homogeneously dispersed.
Common Practical Applications
The technique of creating a 1:10 dilution is employed across many different fields to reduce strength to a workable concentration. In clinical and analytical laboratories, a 1:10 dilution is routinely used to prepare patient samples or chemical standards so their concentrations fall within the measurable range of testing equipment. Microbiology labs frequently use this ratio in a series to count bacteria or other microbes by systematically reducing the concentration to a countable number on culture plates. Outside of a laboratory, a 1:10 ratio is a standardized recommendation for creating household cleaning and disinfecting solutions from concentrated products. Gardeners also use a 1:10 dilution for certain concentrated liquid fertilizers to prevent chemical burn on sensitive plants and ensure the proper delivery of nutrients.