Making a dilution is a fundamental technique in fields ranging from chemistry and biology to household cleaning and cooking. This process involves reducing the concentration of a stock solution by adding a solvent, typically water. Understanding how to perform a simple dilution is an important skill for achieving the correct concentration for experiments or practical applications. The 1:2 ratio is one of the most basic and common calculations encountered.
Defining the 1:2 Dilution Ratio
The “1:2” dilution ratio describes the final composition of a solution. This ratio signifies that the final mixture contains one part of the original substance (solute) for every two total parts of the final solution volume. Consequently, the solution has been diluted by a factor of two, meaning the final concentration is exactly half of the initial stock concentration.
To achieve this ratio, one part of the concentrated solute is combined with one part of the diluting medium (solvent). This combination results in a final solution that has a total volume of two parts. For example, a 1:2 dilution of juice concentrate means using one cup of concentrate and adding one cup of water, yielding two cups of diluted juice. The second number in the ratio always refers to the total volume of the final solution, not the volume of the solvent alone.
Calculating the Required Components
The calculation for a 1:2 dilution requires determining the volumes of solute and solvent needed to reach the target total volume. Since the final volume (Vf) must be twice the volume of the initial stock solution (Vi), the volume of concentrated material needed is half of the desired final volume.
For example, to prepare 100 mL of a 1:2 solution, the volume of solute is calculated by dividing the final volume by two: 100 mL / 2 = 50 mL of the concentrated stock. The remaining volume is the solvent, found by subtracting the solute volume from the final volume: 100 mL – 50 mL = 50 mL of solvent. This 1:1 volume addition of solute and solvent ensures the final concentration is halved.
Step-by-Step Mixing Procedure
The physical process begins with the precise measurement of the concentrated material. Use a calibrated measuring tool, such as a graduated cylinder or pipette, to accurately dispense the calculated volume of the solute. Transfer this measured volume of the initial stock solution into the final mixing container.
Next, introduce the solvent, which is often distilled water, into the container. When diluting strong acids or bases, it is standard practice to add the concentrated material to a volume of solvent, not the reverse, to manage heat generation. Add the calculated volume of solvent to the solute; the final volume in the container should match the total volume calculated earlier.
Once both components are added, the solution must be thoroughly mixed to ensure the solute is uniformly distributed. This is typically accomplished by gently swirling the container or, if stoppered, by inverting it multiple times. Thorough mixing is necessary to achieve the true diluted concentration.
Necessary Equipment and Safety
Accurate dilution relies on using precise measuring tools, such as volumetric flasks or graduated cylinders. Volumetric flasks are preferred when the final volume must be highly accurate. Graduated cylinders offer a slightly lower level of precision but are suitable for general dilutions. Smaller volumes of concentrated stock may require using a pipette to measure the solute accurately.
Handling concentrated solutions requires adherence to basic safety protocols. Appropriate personal protective equipment (PPE) should always be worn to protect the eyes and skin from accidental contact. The dilution process, particularly when working with volatile chemicals, should take place in a well-ventilated area, such as under a fume hood, to prevent the inhalation of fumes.