Alkalies and alkaline earths are discovered in the following manner: Blue litmus paper should be colored pale red by diluted vinegar and dipped into the water; if the former blue color is restored, the water has alkaline properties. In some mineral waters they occur in relatively large quantities, and give to the waters some of their medicinal properties. In waters used for potable or industrial purposes, the presence of potash or soda has no undesirable effect.

Tests For Air, Oxygen And Acid

Whether water contains dissolved gases or air may be found by raising the temperature of the water slowly, until globules of air appear on the sides of the vessel and the bulb of the thermometer. They are generally distinct at about 70° Fahrenheit.

A ready mode of testing the aeration of water for oxygen is by the use of sulphate of iron. This salt oxidises very rapidly, and leaves a deposit of protoxide of iron in a yellow state. If the water is boiled previously, it remains perfectly clear.

If a milky appearance follows the addition of lime-water before, but not after the water under test has been boiled, it contains carbonic acid. The addition of muriatic acid removes the cloudiness.

Another test is as follows: Add from five to ten drops of a solution of oxalate of ammonia to water in test-tube. If the water will show after a little while a clouded or milky appearance before, and not after a short boiling of the water, it is a proof of the presence of free carbonic acid: but if it takes place also after the boiling, then it must be carbonate of lime.