A determination by weight; e.g. in the older method of $\ce{Cl^{−}}$ ion determination, a weighed amount of sample is dissolved in water, $\ce{AgNO3}$ solution added, $\ce{AgCl}$ is precipitated, dried and weighed. From the known mass fraction of silver in $\ce{AgCl}$, the weights of the initial sample and that of the $\ce{AgCl}$ precipitated, the percentage of chlorine in the sample can be calculated readily.