Defined in Chemtrek as “The presence of the dissolved divalent cations Ca2+ and Mg2+. . . (which) gives natural waters chemical properties”, hard water has always been a curse to both animals and man 1 . It promotes scale, the buildup of magnesium and calcium to the point where a rock-like substance forms in household and industrial pipes, disrupts natural habitats and reproductive cycles of fresh water fish, and causes many health-related problems in humans 2 . To avoid such problems, it is important to understand ways that commercial businesses and homeowners can test for hard water. This experiment examines two possible methods of testing water hardness. They include: AA spectroscopy, which measures a water sample's absorption of Ca 2+ and Mg 2+ , and EDTA titration, which uses a titration's end-point to determine the concentration of Ca 2+ and Mg 2+ present in a water source 1 . It is also important to learn about water softening, a process that removes calcium and magnesium from water sources 3 . For this experiment, I explored water softening techniques such as divalent cation removal ion exchange and water softening with a commercial water-conditioning agent 4 .
My group decided to test AA spectroscopy, EDTA titration, and water softening techniques on four natural water samples from Little Chickies Creek in Mount Joy,PA; Allegheny River in Warren, PA; Stone Valley Lake in State College, PA; and a pond on Orr Avenue in Apollo, PA because it is imperative to know about the quality of Pennsylvania's waterways. My hypothesis stated that the water from Little Chickies Creek would be the hardest because it is located by several limestone quarries, which deposit calcium and magnesium into creeks and streams 5 . I proposed that the water from Stone Valley Lake would have the second highest levels of calcium and magnesium because it is also in an area with a lot of limestone. I also proposed that the water from the pond on Orr Avenue would be the third hardest since the surrounding area has some limestone. However, I presumed that the water from the Allegheny River would be the softest because it has been affected by Acid Mine Drainage, a process where run-off from coal mining seeps into water sources and raises its acidity and pH, therefore lowering its hardness 6 .
After completing the experiment, I used the data to calculate the hardness of each sample, classify the samples as soft (0-60ppm), moderate (61-120ppm), hard (121-180ppm), or very hard (over 180ppm), and determine if my hypothesis proved correct 7 . These results are not only important in the context of this lab, but they can inform people on how hard water affects both themselves and the environmental community.
First, I examined my water sample from Little Chickies Creek and determined that the water needed to be filtered for excess particles. Once the water was filtered, I verified that my water sample contained nonvolatile...