by Naomi White, Science Teacher, Jefferson High School, LAUSD

STUDENT HANDOUT

Background and Information:

Hardness is a measurement of the amount of magnesium and calcium in thewater. Water with a lot of magnesium and calcium is considered "hard" whilewater with little magnesium and calcium is considered "soft". When peopleuse hard water, it takes more soap to create suds than with soft water.Hard water leaves behind more mineral deposits of magnesium and calciumthan soft water. Los Angeles has hard tap water because some of ourdrinking water comes from the Colorado River, a river with a lot ofminerals. You will also test for copper and iron, two other minerals thatcan be found in tap water.

Laboratory Procedure:

Total Hardness Test:

1. Fill the test tube (the glass tube with the blue top) up to thesecond line with the water sample.
2. Add five drops of hardness reagent #5. Mix.
3. Add 1 hardness reagent #6 tablet. Shake until dissolved. It willturn red.
4. Use the eye dropper to add hardness reagent #7 one drop at a time.Swirl each time. Count the number of drops until it turns blue.
5. Multiply the # of drops by 10 to find the ppm for the totalhardness.

Calcium Test:

1. Fill the test tube up to the second line with the water sample.
2. Add six drops of sodium hydroxide and mix.
3. Add one calcium hardness indicator tablet. Shake until it dissolves.It will turn red.
4. Use the eye dropper to add hardness reagent #7 one drop at a time.Swirl each time. Count the number of drops until it turns blue.
5. Multiply the # of drops by 10 to find the ppm for the total calcium.

Magnesium Test:

1. Subtract the calcium results from the total hardness to find theamount of magnesium.

Iron Test:

1. Fill a tube to the 5 ml line.
2. Add 5 drops of Iron 1 and one Iron 2 tablet.
3. Cap and shake the tube to dissolve tablet.
4. Allow color to develop for 3 minutes. If copper is to be tested,begin test now. If not go to the final step.

Copper Test:

1. Fill a tube to the 5 ml line.
2. Add three drops of Copper 1.
3. Cap tube and shake to mix. Go to final step.

Final step: Remove caps. Place tube bottom above appropriate standards.Hold ColoRuler at 45 degree angle with natural light coming over yourshoulder. Looking down through tube, match color and record result. Rinseeach tube thoroughly after each test.