Testing Water and Soil
Experiment #12: Creating a Combination Filter (old name lab1, part 1)

Read the whole experiment before starting it. It will give you a better idea of the whole process.

What we learned from experiment #11 can help us design a combination filter that will filter most pollutants.

We learned that the dual resin will remove any positive or negative ions. These might be salts, such as sodium chloride (NaCl) which is Na⁺ and Cl^- in water. It can also trap any organic compounds that have a plus or minus charge. It won't trap large neutral molecules, but activated charcoal will.

Let's begin with the items that would be useful for this lab (but not mandatory) that you can buy at a grocery store. There are two items.

#1. Distilled water: This is not the same as bottled drinking water. Distilled water is made from steam that is cooled and collected. It is supposed to be free of any salts (minerals). An alternative to distilled water is deionized water. Deionized water is water that has been passed through resins that capture all dissolved salts. You use these to rinse off glassware so there are no mineral spots or where you want pure water.

#4. Drying Tube: This plastic tube with tapered (barbed) ends is normally packed with material to absorb water and dry air. Hence, the name "drying tube." We will pack it with materials that will absorb impurities from water. The drying tube has two caps, each with tapered (barbed) ends.

Open up one of the test tubes labeled, "Ion Exchange Resin Deionizing Type."  Pour the contents into the drying tube. The resin is damp so it sticks to itself, so you will have to tap on the test tube to get most of it to pour into the drying tube.

The word "ion" means something that has a charge. The name "Ion Exchange Resin" hints that one ion (charged particle) will be exchanged with another ion. The name "Deionizing type" indicates that all ions will be removed. Remember "De" means to take out.

Uncap one of the activated charcoal test tubes. The activated charcoal pours very easily, so be careful that it doesn't spill over. The only thing that dissolves charcoal is molten iron.

You may not have room for all of the activated charcoal from the test tube. It's OK to leave some in the test tube.

After pouring in the activated charcoal, place another cotton ball into the top of the drying tube. You will probably have to use fingers to pack it inside. Fortunately, the filter can trap contaminants from the fingers.

(Take a picture at this point. See if you can set your camera to either 1600x1200, 1280x960, or 1024x768. If you own a 2 megapixel camera, just use the highest setting [3 stars].)

Food colorings are extracts from plants. Activated charcoal is good at absorbing organic compounds (substances in plants or animals). To see that our activated charcoal is doing its job, we need to add a drop of food coloring to water the 250 mL beaker. This is the water we will filter. You can use the plastic pipette to do the transfer. The small 50 mL beaker has distilled water in it for rinsing out the pipette. I use a saucer to protect the counter top from the food coloring.

Add one or two drops of the food coloring. Return the remainder of the food coloring to the food coloring vial. Then you can use the pipette to stir the food coloring in the beaker by sucking water up into the pipette and squeezing it out.

Be sure to put the cap back on the food coloring vial.

So here's the setup before you begin using the syringe to inject water into and through the filtering tube. It might not be a bad idea to have it all sitting on a paper towels to catch any leaks.

(Take a digital picture of your setup at this point. If your camera is a 2 megapixel camera or higher, you can reduce the resolution to save space. Good sizes are 1600x1200 or 1024x768. On the cameras that use the star (***) system, two stars are fine. A picture from a cellphone camera is not the best, but it would be OK if you don't have a digital still camera.)

Draw some of the tap water into the syringe. The blue tubing will push onto the tip of the syringe.

Once you fill the test tube to over half way, pick up the "drying tube" filter and move it to an empty test tube next to it. Notice the green color is gone from the water, so the activated charcoal is working. But we need to see if the ion exchange resin is taking out the minerals.

Notice the hardness test strip has a color hue that is closer to color square for 0 ppm. It is more turquoise rather than the purplish color before the water was filtered. Report what reading you get with your filtered water.

Take a photo of your color chart with your hardness test strip next to it. This is a close up, so if you camera has a "tulip" icon for taking close-ups, try using that.

In past labs, I had students our the filtered water from the test tube to the bottle labeled, "Purified Water." But now, we are filling the "Purifed Water" bottle with store bought distilled/deionized water to be sure we have pure water.

To prove you were there, I need a picture of you. This is Melissa from the 2004 spring class. She's holding a graduated cylinder and purified water bottle, but you might hold the "drying tube" filter or something else that seems appropriate. Sometimes students' children help out, so it's fine to include them in photos as well.

Send your photos and data to me at costello107@chemistryland.com. Also, note your "Sent" folder may store a copy, which can cause your e-mail storage quota to go over, preventing receiving any e-mails. So you might want to erase the photos from your "Sent" folder after you send the photos.

Congratulations on finishing Experiment #12.