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Did you know?
Reverse osmosis is the finest water filtration method known. This process will allow the removal of particles as small as ions from a solution. It is used to purify water and remove salts and other impurities in order to improve the color, taste or properties of the fluid. R.O. uses a membrane that is semi-permeable, allowing the fluid that is being purified to pass through it, while rejecting other ions and contaminants from passing. This technology uses a process known as crossflow to allow the r.o. membrane to continually clean itself. This is the reason of why an r.o. element can last many years before clogging or need replacement. This water purification process requires a driving force to push the fluid through the membrane, and the most common force is household water pressure or pressure from a booster pump. The higher the pressure, the larger the driving force and efficiency.

WATER ANALYSIS—HYPOTHETICAL COMBINATIONS

Suppose for a minute we analyze the total mineral content of a typical water. This one has, as we shall see, nine grains of minerals per gallon. It could well be the water which Chicago, Detroit, Cleveland or any of a number of other cities draw from the Great Lakes.

Diagrammed, these minerals would appear as shown on the chart below:

Diagram of Mineral Concentration of Water with 9 Grains Total Minerals

NOTE: Analysis for sodium is not usually made directly in a water analysis. Its concentration is estimated by the difference between the total of the anions and the total hardness.

EXPLANATION

The bar at the left in the graph represents the cations of positive ions of the various minerals in solution.

The bar at right represents the anions or negative ions.

Remember that in all compounds the sum of the positive Charges equals the sum of the negative charges. As a water analysts report simply gives the total of various compounds, the same holds true.

Our sample shows positive ions as follows: 5.0 gpg calcium, 2.5 gpg magnesium, 1.5 gpg sodium for a total of 9.0 gpg. The compensating negative ions are: 7.0 gpg bicarbonate, 1.0 gpg sulfate and 1.0 gpg chloride.

A chemist making an analysis of this 9 grain water could report its dissolved minerals in the following manner:

These hypothetical combinations shown above are one of the ways of describing dissolved minerals in water.

Of course, all of the compounds listed would separate into ions when dissolved in water. Thus the various ions, not the complete compounds, would actually be present. However, if a chemist wanted to prepare a water sample having the same chemical characteristics as the sample which was analyzed, he could simply weigh out the amounts of the compounds listed, and dissolve them in water.

When hypothetical combinations are calculated, the ions are combined in their order of increasing solubility. As calcium compounds are generally less soluble than other compounds, calcium is usually first on the list of cations. Magnesium is second and sodium or potassium is last.

Similarly, the anions are used in the following order: hydroxides, carbonates, bicarbonates, sulfates, chlorides, and nitrates.

Note that all the various hardness mineral compounds listed above are expressed in grains per gallon as calcium carbonate (CaC0₃).

In order to make the calculations as shown, the concentrations of the ions must be expressed in such a way that they can be added and subtracted directly. This is similar to the conversion of 1/3 and 1/4 to 4/12 and 3/12 when these fractions are to be used in the same addition or subtraction problem.

Calcium carbonate has a molecular weight very close to 100, (actually 100.089) and an equivalent weight of 50 (50.045). It is possible that this is the reason for its selection as the basic compound, for it certainly simplifies the calculations.

If it is stated that a water has invisible hardness minerals in the amount of 10 grains per gallon as CaCO₃, this hardness may be due to calcium or magnesium carbonates, bicarbonates, sulfates or chlorides or any combination of these compounds. But in every case the combined concentration is chemically equivalent to 10 grains per gallon of calcium carbonate, and the various calculations involved can be made with ease.

The hardness as CaC0₃ of the mineral compounds in water can be determined if the chemical analysis of the water is known. The concentrations of each of the hardness-forming impurities are divided by the equivalent weight of the compound and multiplied by the equivalent weight of CaC0₃. Here are a few of these equivalent weights:

Hardness Producing Compound           Equivalent Weight

Magnesium sulfate MgS0₄                                   60.187

Calcium bicarbonate Ca(HC0₃) ₂                         81.057

Calcium chloride CaCl₂                                          55.493

To determine the equivalent weight of any mineral compound in terms of calcium carbonate:

concentration                equivalent weight of CaCO₃,
                        X
of the mineral                 equivalent weight of mineral

equals the concentration of that mineral as CaC0₃

For example:

10.0 gpg MgSO₄  X  equivalent wt CaCO₃, / equivalent wt MgSO₄, concentration of MgSO₄, as CaCO₃,

10.0 X 50.045 / 60.187  =   8.3 gpg as CaCO₃

Traces of elements or compounds are not normally considered in these calculations. Iron, for example, would not be included, unless present in extremely high concentrations.

In the example shown above, the calcium and bicarbonates are combined first. The excess bicarbonates are then combined with the magnesium. The analysis still does not balance, and the remaining magnesium is combined with part of the sulfates present. The remaining sulfates and all of the chlorides are expressed as sodium compounds. (Adding 5.0 gpg Ca ++ as CaCO₃, to 5.0 gpg HC0₃^- as CaCO₃, produces 5.0 gpg Ca(HC0₃)₂ as CaC0₃, not 10 gpg.)

Table of Equivalent Weights

ANIONS

Hydroxide       17.007

Carbonate       30.005

Bicarbonate     61.017

Sulfate           48.031

Chloride          35.453

Nitrate            62.005

Phosphate       31.657

Fluoride           18.998

Sulfide             16.032

Aluminum sulfate           57.025

Calcium carbonate         50.045

Calcium bicarbonate       81.057

Calcium sulfate              68.071

Calcium chloride             55.493

Calcium hydroxide           37.047

Magnesium carbonate      42.161

Magnesium bicarbonate     73.173

Magnesium chloride           47.609

Magnesium sulfate             60.187

Sodium bicarbonate            84.007

Sodium carbonate               52.995

Sodium sulfate                   71.021 (--> Next article)

Many cities across the U.S. have started to ban traditional water softeners from their communities even though they have hard water. These ion-exchange systems use large amounts of salt, which is then flushed down the drain and harms the environment. Sanitary departments are then forced to build treatment plants to remove the salt and they in-turn pass these costs down to the consumer through higher monthly water bills. Thus many cities have decided that it is not worth the cost and effort and have banned the use of salt-based water softeners altogether.

Salt-free water softeners are a better solution. These systems use catalytic conversion to safely soften water without the use of salts and are much better for our environment and local waterways. Salt-free water softeners deliver all the benefits of traditional water softeners and are approved for use by every community.

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