HOW WATER GETS MIXED WITH LIME.

Throughout a very wide area of territory in the United States and Canada, limestones, or various forms of calcareous rocks, constitute the upper rock stratum immediately underlying the subsoil of the great agricultural regions. During the stupendous operations of Nature in building up this continent, the rocks have been subjected to vast disintegrating agencies: they have been torn and eroded by huge masses of ice; they have been burned by the rays of the unshadowed sun; fractured by the congealing power resulting from deep-searching frost; melted by water,—that most universal solvent in nature; then scattered far and wide by ice and flood. This process has been so complete, that, in the whole limestone territory, all the earth seems charged with lime. Limestones are very sparingly soluble in pure water; but the rain that falls from the clouds is not pure, but contains a charge of carbonic acid that acts chemically upon the lime, forming salts, which the water readily dissolves. Owing to this circumstance, there are few streams, and fewer wells, in the calcareous districts that are not contaminated with lime. The water that passes into streams, generally runs over surfaces that have been washed partly free from lime; and, in consequence of this, creeks and rivers are not so badly tainted with lime-salts as the water in wells that stands saturating the rocks. The appearance or taste of water gives no indication of the quantity of lime held in solution; for the ice-cold well, or sparkling spring, that supplies water so pleasant to drink, may yield so much lime-salts that the water would be ruinous to sheets and flues when used for boiler purposes.

EXPENSE ENTAILED BY USING BAD WATER.

Considering the financial influence of the matter alone, it might be supposed that parties building railroads would exercise diligence in selecting the best water that possibly could be secured for boiler purposes, since the operating expenses are largely magnified by using impure water; but for many years the subject appeared to receive no attention whatever from those best able to regulate the water supply, and water stations were established without any consideration as to the character of the water available.

It is owing to the absence of care in the original locating of water stations, that numerous tanks are to-day drawing their supply from bad wells, where surface water could easily be obtained. Railroad companies are peculiarly conservative about making changes that entail expenditure of money: and existing evils in the water supply arrangements are often continued, because some expense would be incurred in making them; although no kind of money expenditure would bring a more ample return in economy.

EFFORTS OF MASTER MECHANICS TO SECURE GOOD WATER.

The paramount importance of the quality of water used in locomotive boilers, has been long recognized by nearly all master mechanics; for the effect of bad water is brought to their attention in an unmistakable manner. The subject has been frequently before the Master Mechanics’ Association for investigation. A report of a committee appointed at an early meeting to investigate the subject, declares that “Master mechanics have had the conviction forced home, that impure water is the bane of good boilers;” and, even then, a vigorous effort was being made to eliminate the injurious ingredients from the water; and the work was carried on in a hopeful and confident spirit, which was indicated by the words of a subsequent report, which asserted that “Different waters differ widely in the component parts of the impurities they contain, and each requires separate study and treatment;” but the committee were satisfied that the engineering and mechanical skill of railway men could readily devise a suitable appliance for each particular case. In those days, railroad men thought that they could, by mechanical and chemical means, purify bad water, and render it suitable for boiler use. Purifying bad water proved about as difficult an undertaking as reforming the average bad man is recognized to be; and few railroad men can now be found who believe a purifying process can be successfully performed on the large quantity of water needed for locomotive boiler feeding.

LOSS OF FAITH IN PURIFYING METHODS.

The conclusion that artificial methods of purifying bad water can not be carried out in railroad water supply, was not arrived at hastily. It was reached by slow degrees, and through the convincing ordeal of many disappointments, with methods and nostrums that promised to effect the desired results.

Experience demonstrated, that, in the limestone regions, the proper and only way to avoid trouble from lime incrustation in locomotive boilers, is to obtain soft water from streams, or by collecting the rainfall in ponds or reservoirs.

SCALE-MAKING AGENCIES.

Water, as has been mentioned, is the most universal solvent in nature; and what is known as hard water contains many foreign ingredients, but those that exercise such a pernicious influence upon locomotive boilers are lime and magnesia. The scale-making lime appears in two forms,—sulphate of lime, and carbonate of lime. The former is the more dangerous and troublesome scale-making agent; the latter is most frequently met with.

Ordinary well-water will be found to contain solid matter in solution varying from 10 to 100 grains to the gallon. Under 20 grains to the gallon of impurities may be considered fair water if the principal ingredient is carbonate of lime, but that amount of sulphate will make highly objectionable boiler water. Where the use of well-water is unavoidable on a road, quite a saving to boilers can be effected by ascertaining the quantity and character of the impurities received from each water-tank, and directing the engineers to avoid those that contain the worst scale formers.

TO ASCERTAIN THE QUALITY OF WATER.

The proper way to ascertain with accuracy the character of water, is to send specimens to a competent analytical chemist for quantitative analysis. But, as few railroad companies will incur the expense of having the water of the water stations systematically tested, master mechanics may, by a little labor, study, and practice, learn to make tests for themselves that will indicate near enough for practical purposes the character of each water station supply.

As master mechanics are the railroad officials most directly interested in the kind of water supplied for locomotive use, they ought to have direct control of all the water stations on the roads where they are in charge.

APPLIANCES NEEDED IN TESTING WATER.

The chemical apparatus needed for the examination of well-water are, a balance that will weigh accurately to half a grain; an oil stove for evaporative purposes; a few pint porcelain evaporating dishes; a sand-bath, which can be made from a piece of sheet-copper; a dozen test tubes; half a dozen vials to hold solutions of chemically pure chemicals; some pieces of glass tubing; a small mortar and pestle; a supply of filtering-paper; and the vessels needed for measuring accurately. For the solution of the chemical re-agents to be used, a supply of distilled water is necessary; and water of this kind is also necessary to make comparisons with. A piece of pure crystalline ice, when melted, will generally produce water pure enough for experimental purposes.

PREPARING FOR THE EXPERIMENTS.

In bringing in water for examination, it is best to have it drawn from the water-tank into a perfectly clean jug, which should be corked and labeled. Weigh an evaporating dish, noting down the exact weight, and on a sand-bath evaporate one quart or half a gallon of the water to be inspected. When the dish becomes dry, rub off all dust that may be adhering to the bottom, and weigh the dish. The added weight will indicate approximately the total amount of solid matter in the water. Note that down, and every other detail of the experiments.

LIME HELD IN SOLUTION BY FREE CARBONIC ACID.

Sometimes a large quantity of bicarbonate of lime is held in solution by free carbonic acid, which escapes as soon as the water is boiled, leaving the lime to subside in the form of mud. Water of this kind may appear very hard, yet not be very objectionable for boiler use; since the deposit can be blown out if the blow-off cock is used freely. To test this, boil a pint of water for two or three minutes in a perfectly clean dish, then pass it through a filter paper that has been previously dried and weighed. When the operation is finished, dry and weigh the filter paper again; and the added weight will indicate the amount of solid matter held in solution by free carbonic acid gas.

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.

TEST FOR CHLORINE.

The fifth tube we will examine for common salt, which is nearly always present in water. This test is done by dropping in some nitrate of silver solution, which produces a white precipitate, caused by the silver combining with the chlorine, which is the principal element in common salt. This is an excessively fine test, and the nitrate of silver will detect an incredibly small trace of common salt in water. The worst effect that common salt has in water, is to cause priming. Where it is present to any great extent, the blow-off cock should be used frequently on the road; and a surface-cock is quite an aid in keeping the boiler in order. Water that is taken from wells or streams about cities, and found to give strong chlorine re-actions, is nearly always contaminated with sewage.

LEARNING THE MANIPULATION OF TESTS.

Practice in making superficial qualitative tests of water, produces skill in reading the meaning of the various chemical re-actions. This skill can be rapidly developed by practice on prepared specimens. Water for experiments on carbonate of lime can be prepared by dissolving calcite crystals or marble dust in hydrochloric acid, or by mixing chalk with clean rain-water, and filtering it till free from turbidity. While the chalk is mixed with the water, and unfiltered, the specimen will be made stronger by blowing air from the lungs through a glass tube into the water. A preparation for testing sulphate of lime may be made by dissolving some gypsum in distilled water. Fluid magnesia, dropped into pure water, will provide carbonate of magnesia specimens; and Epsom salts will give the magnesia re-action, with the addition that it will indicate sulphuric acid under the chloride of barium test. A grain of salt no larger than a pin-head dropped into a pint of distilled water, will give a distinct chlorine test when nitrate of silver solution is added. Stronger, or even weaker, salt solution can be used by the experimenter while he is working into practice. A small piece of sulphate of iron, dissolved in water, will provide a test for iron.

MAKING QUALITATIVE TESTS.

While pursuing the apprentice practice of tests with these solutions, care must be taken to have the test tubes perfectly clean. Go over the tests in something like the following order. The carbonate of lime test is to be made first. Four test tubes will be used. In the first we put distilled water alone; in the second we put ten drops of the chalk solution; in the third we put twenty drops of the solution; in the fourth we put thirty drops, then add distilled water till all the test tubes are about two-thirds filled. Drop into each tube about the same quantity of oxalate of ammonia solution, and the degree of turbidity will help to indicate the hardness of each specimen. The first tube, containing pure water, will give no re-action if the chemicals are pure.

This process should be extended to all the other solutions, and will be found very helpful. In carrying out experiments of this kind, much assistance will be obtained from having a work like Stuckhardt’s Chemistry at hand for reference.

THE SOAP-TEST FOR HARDNESS.

Most people are aware that hard water has a peculiar effect upon soap, making it curdle instead of lather when used for washing purposes. This peculiarity was made use of some years ago by Dr. Clark of Aberdeen, Scotland, in devising a test for the hardness of water, in which the quantity of a standard soap solution needed to produce a permanent lather on water, indicated the degree of hardness of the water. A modification of the Clark process can be used very conveniently by master mechanics in making superficial tests of the hardness of water, and the plan has the advantage of being easily applied. With a test tube and a small bottle of soap-solution, the investigator is ready at any time or place to make tests; and a few minutes spent over each specimen will give him an idea of the value of the water for boiler purposes.

The original Clark soap-test was made with a soap-solution of known strength, of which a certain measured quantity was required to produce a permanent lather on a gallon of water containing a given quantity of carbonate of lime. The degrees of hardness of other specimens were computed according to the quantity of the soap-solution required to produce a permanent lather. Preparing soap-solution of a certain strength, and water of a certain hardness, for the purpose of indicating a point for beginning the computations, is a tedious operation; and the soap-test can be used in a much simpler way. While making numerous tests of water on the Burlinglington, Cedar Rapids, and Northern Railway some years ago, to ascertain the condition of water tanks at different seasons of the year, and in examining the supply of proposed water stations on extensions of the road, I used the following modification of the Clark process:—

MODIFICATION OF THE CLARK SOAP-TEST.

The Cedar River, during its normal flow in summer, contains about ten grains of solid matter, mostly calcium carbonate, to the American gallon of 58,373 grains. This I considered good boiler-water, and made it the standard of comparison for my tests. Beside the shop, there is a well, which the people who built the road dug for supplying boiler-water; although the Cedar ran a few rods distant. This well-water contained about forty grains of solid matter to the gallon, one-fourth of the impurity being sulphate of lime. This water I made my “awful example” standard of comparison, so that water approaching this in hardness was condemned.

The soap-solution I made by dissolving seventy grains of castile soap, or white soap-powder, in a pint of alcohol. Care must be taken that all the soap is dissolved, and then it is best to keep the mixture in an even temperature not below 60° Fahr. The tests can be made more accurately by having the water under examination brought to the same temperature as the soap-solution.

APPLYING THE SOAP-TEST.

In making the tests, a measured quantity of the Cedar water was put into a stoppered bottle. One ounce of water put into a two-ounce bottle is a convenient quantity. The soap-solution was then measured out with a pipette made to hold thirty drops, and the bottle was well shaken after each measure till it was found that a lather was formed which held on for five minutes. The operation was then repeated; and the last charge from the pipette was put in, drop by drop, till the point where a permanent lather formed was noted. A similar performance was gone through with the bad well-water, and very little practice enabled the operator to ascertain where a specimen of water stood between the range of the good and bad water.

The soap-solution must be kept in a properly stoppered bottle; and, every time a new solution is made, its strength must be tested in the above fashion. The solution deteriorates when kept longer than a month or six weeks.

The degree of turbidity caused by the first charge of soap-solution, is an indication to the practiced experimenter of the degree of hardness of the water.

Most men interested in ascertaining the condition of boiler-water, can devise means for obtaining water of known hardness wherewith to make comparative tests.

If water under examination prove very hard, the test will be more accurately done by diluting it with its own volume of distilled water.

The soap-test is good for lime in all its forms, and magnesia; but the latter impurity uses up more soap than lime does. So, where magnesia abounds in water, the specimen under trial will seem harder than it actually is. Magnesia is also slower than lime in acting upon the soap. Water that contains magnesia will produce a lather when enough solution is put in to overcome the lime present; but if it be allowed to stand a few minutes, till the magnesia acts, the lather will not then form. The presence of certain alkaline salts in water, such as the carbonates and sulphates of soda and potash, injuriously affects the soap-test by making the water appear softer than it is; since they accelerate the forming of a permanent lather. Keeping these facts in mind will often prove of valuable service in making tests of water.

When the soap-test indicates that water contains hardening ingredients, representing more than fifteen grains to the gallon, other tests should be at once made to ascertain what the leading ingredients are.

DIFFICULTIES OF PURIFYING WATER FOR LOCOMOTIVES.

The nostrums offered to railroad managers for purifying feed-water are legion, but it is doubtful if a single remedy has proved entirely successful. In most instances, the material or means used have been worthless or impracticable; but, in other cases, the appliances have not received justice from those attending their application. Most people underrate the magnitude of the task involved in undertaking to render the impurities of feed-water innocent in locomotive boilers. The case of a learned professor who undertook to doctor the feed-water for locomotives on a prominent road, where he made his arrangements for each engine using one thousand gallons of water a day, is representative. When provision has to be made for some engines using double that quantity each hour, the difficulty of the transaction becomes apparent. As has already been said, I believe that obtaining soft surface-water is the proper way to avoid trouble with locomotive boilers; but, where this is impracticable, considerable saving can be effected by “doctoring” the water if the operations are intelligently conducted.

MUD.

Mud is the most universal impurity of feed-water; and, in many cases, it causes the destruction or injury of sheets, particularly the crown-sheets of fire-boxes. Where the water of a road is habitually muddy, it would pay to filter the water, or to have two tanks at each water station, so that a system could be followed of letting the water settle in one tank while the other was in use. The settled mud, by this means, could be washed out regularly before a tank were refilled.

CARBONATE OF LIME.

Dr. Clark, inventor of the soap-test, recommended a method of purifying water containing carbonate of lime, which has been successfully followed in many places, especially in England. It consists of adding caustic lime to water containing carbonate of lime. By this process, 28 grains of caustic lime result in the precipitation of 100 grains of lime carbonate. Or, to put it in a practical shape, where a tank contains 30,000 gallons of water, each gallon being impregnated with 30 grains of lime carbonate, 36 pounds of caustic lime will be sufficient to precipitate the whole of the impurity, making a total deposit of 164 pounds.

SULPHATE OF LIME.

Where the water impurity is principally sulphate of lime, the caustic lime remedy will not work; but a precipitate of the objectionable compound can be made by treating the water with caustic baryta or caustic soda. In the first case, the baryta takes possession of the sulphuric acid holding the lime in solution, allowing the latter to fall down as mud: when the soda cure is applied, the sulphuric acid deserts the lime, and combines with the soda, for which it has greater affinity, leaving the lime to precipitate, unless it be preserved in solution by the carbonic acid that accompanied the soda.

Where the water contains a mixture of lime sulphate and carbonate, the soda treatment may be advantageously used in combination with the caustic lime system.

Attempts have frequently been made to purify water by putting chemicals into the locomotive tenders, the impurity being precipitated in the boiler. The leading objection to this system is, that it leads to enormous quantities of sediment being deposited inside the boiler; since, in some instances, the purifying substance is as bulky as the original impurity. In other cases, the chemical introduced into the boiler causes foaming. Let us take the case of water that contains fifteen grains of sulphate of lime to the gallon, and is treated with sulphate of baryta. To do so properly, one grain of the chemical will be required for each grain of lime. A freight engine uses seventy-five gallons of water to the mile, and runs one hundred miles a day. This is light service, both for water and mileage; yet, within ten days, nearly three hundred pounds of solid matter is injected into the boiler. To purify water by injecting chemicals into locomotive boilers, and prevent the boiler filling up rapidly with mud, or giving trouble from foaming, the blow-off cock and surface cock must be used so frequently as to be felt on the consumption of coal. Where purifying of feed-water must be done, the right place to carry on the process is in the station tanks, or in special appliances beside them. By carefully watching the character of the impurities in the water, and treating them with their proper precipitants, labor and expense devoted to the purification of feed-water may bring in good returns: where attempts are made to improve the water over a whole road by one method of treatment, failure is certain.