TEST FOR LIME SALTS.
Superficial tests that will indicate the condition of the water from the coloring produced by the impurities combining with chemicals that take them out of solution, can be made in the following manner: Five test tubes are half filled with water to be tested. The first one will be examined for lime in any form. A teaspoonful of aqua ammonia is put in the water for the purpose of stimulating the chemical action, then twenty drops of a solution of oxalate of ammonia are added. The degree of turbidity will indicate the quantity of lime in the water. Should the quantity of lime be very small, the test tube would have to be kept in a warm place a few hours before the re-action showed itself.
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.
TEST FOR CARBONATE OF MAGNESIA.
The third test tube may be examined for carbonate of magnesia, which is found freely mixed with the water of many wells. Put aqua ammonia in this tube, and add twenty drops of a solution of phosphate of soda. A crystalline precipitate will indicate the presence of magnesium. Where carbonate of magnesia is present in considerable quantities in water, it sometimes forms along with lime a thick, porous scale; and in other cases it is apt to float on the top of the water, causing trouble by making the boiler foam. If an engine boiler has got scale formed from water free from magnesia, and goes on to a division where this impurity abounds, the magnesia will take off the old scale before it begins to form new incrustation. A few pounds of common salt put into the tender daily will have a good effect in preventing trouble with magnesia; since it forms chloride of magnesia, which is a decided preventive of lime scale.
TEST FOR SALTS OF IRON.
In the fourth test tube we will search for iron salts. A solution of potassa or ammonia will produce, should iron be present, a whitish precipitate, which presently turns to a dirty green, and, ultimately, a reddish-brown color, owing to its absorption of oxygen from the air. A more delicate test for iron is ferro-cyanide of potassium, or sulpho-cyanate of potassium; but other mineral combinations might deceive a novice using these reagents into the belief that iron was present when it was not. A light trace of iron in water is very common; and, so long as it is in minute quantities, the salt seems quite innocent. But occasionally water is found saturated with iron in the form known by chemists as FeSO4. Then it is very objectionable for boiler-feeding; since it exercises a strong corrosive action on the plates, pitting and furrowing being a common result of its action. Scale formed by water of this character is nearly always a hard, thin substance, that sticks with intense tenacity, and generally takes away part of the skin of the iron when it is taken off.