This can be explained by the fact that the edta

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This can be explained by the fact that the EDTA titration tests for all divalent cations, while the AA Spectroscopy results show the hardness values of Mg2+ and Ca 2+only. The Total Dissolved Solid test results were consistent with the other two methods concerning the presence of calcium in the water samples. Distilled water had no precipitate, while the 1.0x10-3 Ca2+had a faint white precipitate form, showing that divalent calcium ions suspended in water left a white residue when heated to the point of evaporation. When comparing the amount of precipitate to the hardness values of the water samples, the
Yealy 13amount of dissolved solids on the aluminum foil increased with increasing hardness values. There was a definite margin for error throughout this experiment. Human error is more likely in the EDTA titration than with the AA Spectroscopy method. The AA Spectroscopy method used a very scientifically technical, expensive Atomic Absorption Spectrophotometer. Before the experiment began, a set of check standards were recorded to aid in the reproducibility of this experiment. These check standards verify the particular calibrations for the spectrophotometers on the particular day of the experiment. The AA Spectroscopy method is more time efficient because more samples can be tested in a smaller amount of time. With EDTA titration,each individual experimenter must determine in which well the solution turnscompletely blue from the original wine red color. This is a subjective determination that may vary from person to person depending on their perception of color. The average percent error of the EDTA titration method was about 25% [11]. This was calculated by using the results of the serial trials, including the titrations of CaCl2 and MgSO4which had concentrations labeled on the bottle of the respective solutions. The calculated standard deviation for the EDTA titration was 180ppm +/- .0002ppm [11]. Overall this method is inexpensive, but not entirely as accurate as the AA Spectroscopy.Using Arm and Hammer Super washing soda was an effective method of softening the water because the active ingredient in this washing soda is NaCO3. The sodium ions from this compound effectively soften the water by
Yealy 14replacing the divalent cations in the water sample. For the Conewago creek water, the original hardness value was 180ppm, but after the washing soda was dissolved in the sample, EDTA titration showed the water to be softened,at a hardness value of 40ppm [11]. The method of Divalent cation removal was a more effective method of softening because the calculated hardness from EDTA titration after the exchange took place was 0ppm which means the water was completely softened.According to The Water Encyclopedia, there are 4 standard classifications for the hardness of water. Values reported by the United States Geological survey state that water is considered soft from 0-60mg/L, moderately hard from 61-120mg/L, hard from 121-180mg/L, and very hard

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