Note 75 — Chapter VIII · ABSORPTION BY SOILS.
Reading edition
The prompt absorption of a base by soils is shown by the following experiment: To some freshly boiled distilled water add several drops of alcoholic phenolphthalein, and then just enough base to produce a decided red color. If the solution be now passed through a short column of soil, cotton, shredded filter-paper or similar absorbent, the percolate will be perfectly colorless. The red color will be restored, however, by adding a little of the base to the percolate.