Parts per million (ppm) is a unit used to express very small concentrations of a substance in a mixture or solution. It represents the number of parts of a substance per one million parts of the total mixture. For example, 1 ppm means one part of a substance in one million parts of the solution or mixture
. PPM is dimensionless and often used to measure concentrations in gases, liquids, or solids. It is equivalent to 1 milligram of substance per liter of water or 1 gram of substance per 1,000 kilograms of solution, depending on whether volume or mass is used
. In practical terms:
- 1 ppm can be thought of as 1 unit of solute in 1 million units of solution.
- For example, 1 ppm is like having one red cube in 999,999 blue cubes, where the red cube is the substance being measured and the blue cubes are the solvent
- In atmospheric chemistry, ppm is used to describe gas concentrations, such as pollutants in air
PPM is widely used in fields like chemistry, environmental science, water quality testing, pollution monitoring, and industrial process control. It helps quantify very small amounts of substances to assess quality, safety, or performance
. How to calculate ppm:
ppm=(mass or volume of substancetotal mass or volume of solution)×1,000,000\text{ppm}=\left(\frac{\text{mass or volume of substance}}{\text{total mass or volume of solution}}\right)\times 1,000,000ppm=(total mass or volume of solutionmass or volume of substance)×1,000,000
For example, if 0.2 grams of salt is dissolved in 1 liter (about 1 kilogram) of water, the ppm concentration of salt is:
0.2 g1000 g×1,000,000=200 ppm\frac{0.2\text{ g}}{1000\text{ g}}\times 1,000,000=200\text{ ppm}1000 g0.2 g×1,000,000=200 ppm
This means the salt concentration is 200 parts per million in the water
. In summary, ppm is a precise and standardized way to express very dilute concentrations, useful across many scientific and industrial applications.
