1. SPECIFIC GRAVITY

2. INTRODUCTION Defined as the ratio of the weight of a substance to the weight of an equal volume of another substance that is determined to be the standard. Written as a decimal Water is the standard for liquids and solids. Water has a specific gravity of “1”, which means that 1 mL of water weighs 1 gram.

3. Why Do We Need Specific Gravity? There will be times when you need to know the weight of a liquid or the volume of a solid, especially when you are compounding. The specific gravity for most substances can be found in pharmacy references.

4. Solving Problems Equation: SG = weight of substance (grams) equal volume of water (mL) For example: If 5000 mL of a substance weighs 6565 g, what is the specific gravity of the substance? Answer: 1.13 (6565 ÷ 5000 = 1.13)