Last updated 3-15-08
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Testing Water & Soil
Experiment #11: Testing Water Filters
(old name was Lab5)

Understanding the strengths and weaknesses of filters is important in knowing the quality of the water that comes out the filter. Filters can do three things.
1) They can improve the quality of water.
2) They can do nothing.
3) They can make it worse.

It depends on what they are designed for and if they are scientifically valid. In other words, many companies make their products sound scientific but on closer scrutiny you are apt to find misinformation.


For example, many companies sell water "conditioning" devices that are supposed to do the same as traditional water softeners. Anyone who understands chemistry can discover for themselves the truth about these kind of products. They can decide if their money can be better spent on something else that really works.
What we want to do for this experiment is to see how different filter materials perform. On the right is activated charcoal. Next to it is ion exchange resin (Sodium type). The middle one is ion exchange resin (deionizing type). Then there are two magnets, and the left one is tap water only.

This graphic is from Lab 1. It says that activated charcoal is good for removing organic compounds. This includes pesticides, certain fertilizers, and many decay products from plants and animals. Organic compounds are usually responsible for bad tastes and smells. So activated charcoal can be good in helping there. What it is NOT good for are dissolved salts. These salts make water "hard." Dissolved salts are too small for the charcoal to trap, plus because salts are charged, water pulls on them and keeps them from sticking to the charcoal.

Dissolved salts have positively charged metal ions like sodium ion (Na+), potassium ion (K+), calcium ion (Ca2+), copper ion (Cu+/Cu2+), and dozens more metal ions. >>> The negative half of these salts are chloride (Cl-), fluoride (F-), carbonate (CO32-, nitrate (NO3)2-, hydroxide (OH)-, arsenate (AsO4)3-, and dozens more. >>>Notice in the picture, water surrounds the ions. The negative end of water will attracted the positive metal ions. The positive end of water the negative ions. The bites out of the positive metal ions means some other atom took an electron away. The bumps on the negative ions represent the extra electron(s) it has gotten from the metal ions.

The Ion Exchange Resin Deionizing type (below) is good at removing the dissolved salts (minerals) that activated charcoal can't. It has two resins. The black resin spheres absorb the positive metal ions and the clear spheres absorb the negative ions like chlorides and carbonates. To keep charges balanced, the positive metal ions are replaced with positive hydrogen ions. The negative ions are replaced with hydroxide ions (OH-). If this resin only had black spheres, the positive hydrogen ions (H+) released would cause the water to become quite acidic (not good)...  Notice that when Ca2+ is absorbed two H+ ions must be released so that the charge in the water stays balanced.
...Fortunately, the clear resin spheres are releasing an equal number of negative hydroxide ions. What you should learned already is that H+ and OH- will combine to form water. So the beauty of this resin is that the salts are absorbed and pure water takes their place. This dual resin goes beyond just softening water. It removes all dissolved ions. The drawback is the spheres will reach a limit of how much salt it can absorb. When this happens, the resin has to be thrown out and replaced with new resin.
The Ion Exchange Resin (Sodium Type) is similar to the previous resin. However, this is only made up of one type of resin. Like the clear resin above, this one also attracts positively charged ions. This one however, doesn't release H+, but releases sodium ion (Na+). The action of removing calcium ions (Ca2+) and magnesium ions (Mg2+) makes this a water softening resin. Potassium is removed even though it doesn't need to be to "soften" water. Removing copper and certain other metals is a healthy outcome of this resin. Note that the negative ions of salts are not touched by this kind of resin.

This type of resin is commonly used in home water softening systems. Let's reveiws the pro's and con's.
Pro's: It removes the calcium and magnesium ions that interfere with soaps and some cleaners.
Pro's: It removes some metals that are not healthy (copper, lead, chromium, tin, and more).
Pro's: By passing concentrated salt solution (NaCl) through the resin, the trapped metal ions can be flushed away as new sodium ions regenerate the resin's ability to soften water. This is why we add bags of salt every so often in our water softeners.
Pro's: Sodium salts are more soluble than most other salts. So cleaning water spots and scale made from sodium salts is easier.

Con's: It removes all metal ions (minerals) except for sodium. Some that are healthy like calcium. Potassium is considered healthier than sodium. People who are on low sodium diet (like for heart problems) should not be drinking water coming through this kind of water softener.
Con's: This water softener does not remove the salts (minerals), it just makes them all sodium type of salts.
Con's: It does not remove most organic type of pollutants unless they are positively charged.

Magnets have always fascinated us. They seem so mysterious. Here is a picture of the Levitron. The spinning top floats above the surface. I own one myself and marvel at the "magic" of levitation. This "magic" may be possible with a spinning magnet and a fixed magnet. But can magnetic forces perform magic with body therapy or water softening?

Here's a quote describing the book, Magnet Therapy: "Magnet Therapy presents the history and science of this fascinating subject, explaining in clear language why magnets increase oxygenation in the blood, reduce cholesterol levels and blood pressure, reduce pain, enhance cellular regeneration, and may even inhibit tumor growth."
Here's a quote describing the other book, Bad Medicine: "The idea of bloodletting or shock therapy as cures for what ails you seems antiquated and foolhardy. However, Wanjek believes that many people believe in and practice equally bogus medical treatments today. He debunks many common medical myths and misconceptions, including touch therapy, magnet therapy, and the use of shark cartilage to ward off cancer."

As you can see there are some opposite views as to the validity of magnet therapy. But those who believe in magnet therapy will probably buy into the idea of magnetic water softening.

Here's a quote from the site who sells these products. "Magnetically treated water has been used in Europe and Asia for many years. In the past 10 years this “new” idea has become widespread in the United States. It requires no pipe cutting, electricity or maintenance and lasts virtually forever. Just place the units over the pipe and attach with the included plastic ties.When water is magnetically charged, it electrically takes on a greater ionic charge than the minerals, which creates a natural magnetic attraction between the two. The magnetization then attracts and locks the dissolved minerals into the water creating healthy and cost-free de-scaling. Softening and better tasting water are the outcome of an actual reduction in the size of the water molecules. The small, magnetized water molecules have a greater solvency and a magnetic attraction that results in cleaner bathing and washing, and dramatically reduces the gases and foul taste of sulfur, chlorine, fluoride, etc."

A common approach of all these pseudoscience products is the use of technobabble (technical descriptions that are meaningless and have no basis in real science) and wonderful claims (Note words like: wide-spread use, easy, lasts forever, no maintenance, healthy, cost-free, dramatic.) They often succeed in selling these products for these reasons:
1) Most people are ignorant of physics and chemistry.
2) People love things that are cheaper and easier.
3) People want to believe what others are saying. Especially when they are saying such wonderful things.
4) The saying, "A fool and his money are easily parted." is sadly true.
5) People are generally too lazy to check things out for themselves to see if they are valid.
6) When something works, people often jump to the conclusion of why it worked. The credit is often given to something that had nothing to do it.

Before we move on let's analyze some of the technobabble used to promote the product.

"When water is magnetically charged, it electrically takes on a greater ionic charge than the minerals, which creates a natural magnetic attraction between the two."

They are confused about magnetism and electrical charge. "Magnetically charged" makes no sense because charge comes from only electrons or protons, not magnetism. Have you ever heard of someone using a magnet for a battery? Again, by saying "a greater ionic charge...creates a natural magnetic attraction..." they are still confused about these two entirely different forces. Plus the only way water can have "a greater ionic charge" is for it to absorb an acid (a positive hydrogen ion, which doesn't come from magnets, only acids). But even then it would repel the positive metal ions (because like charges repel) and not "create a natural magnetic attraction."

Just reading this technobabble is annoying and painful to us who understand chemistry and physics.

In this lab, you will see for yourself the effectiveness of magnets in water softening. These magnets are small but are neodymium magnets, which are the strongest permanent magnets made. It's the same kind of magnet that often gets mentioned in the magnetic water "conditioning" ads.
Your kit has all items needed for this experiment.

#1, 2, &3: You will be using both Ion Exchange Resins (Sodium type and Deionizing type). You will also use the activated charcoal.

#4: Your kit also has two small neodymium magnets. They are stored in a small ziploc bag.  In some kits, the magnets are small cubes.   They work the same.

#5. You will be using the small 50 mL beaker for holding the tap water.

If your residence has a water softener, you need to get the water from an outside faucet. That water does not go through the water softener.


#5 & 6: You will be using the food coloring that came with your kit (may be red, yellow, blue, or green) and just the Hardness test papers.
#7: You will also use five empty test tubes.

#8: You will be using the Color Chart..



Fill the small 50mL beaker with tap water.

If your residence has a water softener, you need to get the water from an outside faucet. That water does not go through the water softener.

This is how the 5 test tubes will look like once the filter materials are added. But first read ahead for more tips on adding the materials to the test tubes.
For the activated charcoal, instead of using the microspatula, you might try just tapping it to help the charcoal drop into the test tube. Put it into the far right test tube (one on right end).
Scoop out some of the Ion Exchange Resin (Sodium type) and place it in the second from the right test tube. Unlike the picture shows, you should have a cap on the other test tubes so that the resin doesn't get into the other tubes.

The Ion Exchange Resin Deionizing type will also require a microspatula to get it out. Place it in the middle test tube. Again, the caps to the other test tubes should be on so some of this doesn't fall into the wrong tube. That was the mistake I made, and it took a while to fish out the stray particles.


Drop the two magnets into the second test tube from the LEFT.

The far left test tube is left empty.

The tap water is now added to each test tube. Fill the test tubes to about half way.

After the tap water has been added, you should have this line up. From Left to Right. Tap water only, magnets, ion exchange resin (deionizing type), ion exchange resin (sodium type), and activated charcoal.

With the cap on the test tube, turn the test tube with the activated charcoal up and down to mix the water with the activated charcoal. Or you can shake the tube. Do it for about 1/2 a minute.
Do the same with the sodium ion exchange resin test tube. (You might notice I have more than half a tube of water. This was how I started the lab. But later I realized the resin would work better with less water. So my instructions ended up saying to use about half a tube of tap water)
Next comes the dual ion exchange resin (deionizing type).
The magnets get their turn. Do NOT shake the test tube with magnets, the test tube can break.  Just rock the test tube back and forth until the water gets plenty of contact with the magnets.
You will need the hardness test papers next. I believe you should have 4 papers left. Which isn't enough to test all 5 test tubes. However, you already tested the tap water in the previous experiment. So just test the right 4 test tubes. As the chart says, just dip it in and remove immediately and check the chart 15 seconds later.

HARDNESS Results : Here I have the results from all 5 test tubes (remember you probably only have enough to do the right four.)

The results show that the two ion exchange resins brought the hardness to zero. The water in the other test tubes all read the same as the original tap water.

Remember hardness is measuring the amount of calcium and magnesium ions in the water. These are the ions that bind to soap and keeps it from making suds and available for cleaning. Calcium bound to soap comes out of solution and forms soap scum.

(Take a picture of your test tubes at this point in the lab.) Also report your values to me when you send the picture.

The activated charcoal didn't help in reducing the metal ions calcium and magnesium. Of course, it was not expected to help. These ions are too small for the crevasses in activated charcoal to hold. But large compounds can be captured with activated charcoal.

Food coloring contains dyes from plants or animals. These are usually large organic compounds. You can use the food coloring that came with your kit to test activated charcoals ability to absorb it. Fill your small beaker with distilled water and then place one or two drops of the dye in the water. Notice I placed a saucer under the beaker to protect the counter top.

Now add about 1 or 2 drops of the colored water to each of the test tubes. Remember, you may have a different color than shown here.

Trivia: There are only 9 color additive certified to be used in food for humans in the United States.

This is what my test tubes looked like after adding the diluted green food coloring. The next thing to do is to shake the tubes again to see if they absorb this colored organic molecule.
After shaking, I noticed that the middle test tube with the dual ion exchange resin (deionizing type) had absorbed the green food coloring. However, the activated charcoal was not settling and I couldn't see the color of just the water. What you can do is take half of a cotton ball (from your kit) and push it into the test tube with the activated charcoal. As the cotton ball goes down, water will come up through it and be clear (see pic below).

Take a picture of your test tubes at this point in the lab and report which test tubes are clear and which have a greenish tint [or whatever tint of dye you have].

Here is the final line up. The test tube with only tap water is still greenish as expected. The water with the two magnets still has some green tint to it, so magnets apparently don't absorb organic molecules. The middle test tube with the dual ion exchange resin cleared up the water nicely. The ion exchange resin (sodium type) did not absorb this organic compound. The activated charcoal did. So what does this tell us? Being absorbed by the activated charcoal means that it is a relatively large organic (carbon-based) compound. The behaviour with the two resins indicate that the green food coloring molecule is probably negatively charged. Remember, the sodium ion exchange resin absorbs positive metal ions like calcium+2. It would also absorb any positively charged organic compound. But since it didn't, we can assume the green dye is not positive. The dual resin, however, can absorb both negatively and positively charged compounds.

Here is the structure for FD&C green # 3. You can see it is a large compound, which is why the activated charcoal trapped it.
In water the three sodium ions (Na+) will get carried away by water molecules. The main structure has three SO3- groups (3 negative charges) and one positive charge on the lower nitrogen atom (N+). Overall the molecule would have a net charge of a negative 2 [(-3) + (+1)=(-2)]. That it why the sodium ion exchange resin did not trap it, but the dual resin did.
FD&C Blue #2 is this structure. (Almost the same as the green dye above.) It comes from the Indigo plant, which has blue flowers. This dye has been used for centuries and is also the dye used for blue jeans. It doesn't bind to cotton very strongly, which allows blue jeans to get that faded look. If we wanted our blue jeans to fade faster, we could add some of the dual ion exchange resin (deionizing type) to the wash. Activated charcoal would help it fade also, but it would stain the cotton with black carbon particles.

(As always, I need a picture of you doing some step in this lab. Perhaps take a picture of you shaking a test tube or holding up a test tube and looking at it.)

Email the results you got to me along with the three pictures from this lab.

SinceApril 18, 2004
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