Alkalimetry, the process employed to estimate the quantity of alkali present in any mixture. Its principle consists in exactly neutralizing a certain weight of the alkali, and knowing the quantity of acid of a given strength which is required to effect this. The alkaline substance, carefully weighed, is dissolved in warm water, placed in an alkalimeter, which is usually a graduated glass tube, and diluted sulphuric acid cautiously and slowly added till the solution is made neutral. This is known by the use of little bits of test paper in the liquid, which, by their change of color, indicate the slightest acid or alkaline reaction. The process may be reversed to test the strength of acids, and is then called acidimetry.