1. What is the Alligation Method?

The alligation method is a mathematical technique used in pharmacy to calculate the relative proportions of two solutions of different concentrations needed to prepare a solution of intermediate concentration.

2. How Does the Calculator Work?

The calculator uses the alligation formula:

Where:

• \( \text{High} \) — Higher concentration component (%)
• \( \text{Desired} \) — Target concentration (%)
• \( \text{Low} \) — Lower concentration component (%)
• \( \text{Ratio} \) — Parts of high concentration to parts of low concentration (dimensionless)

Explanation: The ratio tells you how many parts of the higher concentration solution to mix with how many parts of the lower concentration solution to achieve the desired concentration.

3. Importance of Alligation Calculations

Details: Alligation is essential in pharmacy for preparing customized concentrations of medications, especially when stock solutions of different strengths are available.

4. Using the Calculator

Tips: Enter all concentrations as percentages. The high concentration must be greater than the low concentration, and the desired concentration must be between them.

5. Frequently Asked Questions (FAQ)

Q1: What if my desired concentration equals one of the inputs?
A: If desired equals high, use 100% high solution. If desired equals low, use 100% low solution. The calculator will show "Undefined" in these cases.

Q2: Can I use this for non-percentage concentrations?
A: Yes, as long as all concentrations use the same units (mg/mL, g/L, etc.), the ratio calculation remains valid.

Q3: How do I apply the ratio in practice?
A: The ratio tells you the relative parts to mix. For example, a ratio of 2 means mix 2 parts high with 1 part low concentration solution.

Q4: What if I get a negative ratio?
A: Negative ratios indicate invalid inputs where desired concentration is outside the range between high and low concentrations.

Q5: Can this be used for more than two components?
A: For multiple components, you would need to perform multiple alligation calculations or use an alternate method.