How Do You Spell PART PER MILLION?

Part per million (ppm) is a unit of measurement used to express the concentration of a particular substance in a solution or mixture. It is a dimensionless quantity that represents the proportion of the substance in terms of the number of parts of the substance per million parts of the mixture.

In other words, a concentration of 1 ppm means that there is one part of the substance being measured for every one million parts of the mixture. This is equivalent to one milligram of the substance per kilogram (mg/kg) or one microgram of the substance per gram (µg/g).

Part per million is commonly used in various fields such as environmental science, chemistry, and toxicology to quantify the level of pollutants or contaminants in air, water, soil, food, or other substances. It allows for the comparison and understanding of very small concentrations, particularly when dealing with substances present in trace amounts.

The unit ppm is preferred when working with extremely low concentrations, as it provides a more manageable and comprehensible scale compared to working with proportions or percentages. It simplifies the expression of minute concentrations that can be difficult to represent using standard units due to their small values.

It is important to note that part per million is based on a ratio scale, meaning that it considers the amount of the substance being measured relative to the whole mixture. The concentration of a substance can range from zero ppm (absence of the substance) to higher values indicated by the number of parts per million.