TEST FOR SULPHATE OF LIME.
The water in the second test tube will be examined for sulphate of lime. A few drops of hydrochloric acid are first put into the water, then twenty drops of chloride of barium. A white precipitate, which generally makes its appearance at once, indicates the presence of sulphuric acid. In water belonging to the calcareous regions, it may safely be concluded that the sulphuric acid is held in the form of sulphate of lime. An exception has sometimes to be made for water drawn from the vicinity of coal mines, and such places, where sulphate of iron abounds. Water that holds sulphuric acid in this form is readily identified by a test for iron salts.
When it is found that water gives a strong re-action indicating sulphate of lime, the inference may safely be drawn that the tank it came from should be avoided.