# Which measure of concentration is best used when working with small concentrations?

Jul 9, 2016

#### Answer:

Perhaps $\text{ppm}$, $\text{parts per million}$?

#### Explanation:

$\text{1 ppm}$ in aqueous solution $=$ $1 \cdot m g \cdot \text{solute per litre of solution}$. At these concentrations, we really do not have to bother about considerations of density.