An Experiment on Soil Analysis
Jacob Pitcher and Derrick Gillespie
Chemistry Lab 112 Section 02
A sample of soil was tested for possible contaminants and other information using a variety of techniques including moisture analysis, pH measurement, acid-base titration, chloride-ion electrode analysis, and flame testing. The sample had a greater concentration of chloride ions, no measurable CaCo3 , and lower than standard moisture content. It was contaminated with KCl and likely HCl ionic solids. Introduction
Soil is a vital component of any environmental network. It provides the basis for life for any environment. There are many factors that determine what life comes from soil such as texture of the soil, topsoil composition, inorganic and organic components, as well the chemical balance of the soil. Needless to say when the chemical balance of soil is altered by a foreign contaminant it has drastic effects on the surroundings. It is important to be able to identify these foreign contaminants so that the proper corrections can be made to the soil to bring the balance back to an habitable state. The primary goals of the experiment was to measure the pH of the soil samples, determine the buffering capacity of the soil samples, Determine the presence and amount of CaCO3 in the soil samples, determine the amount of chloride ion present in the soil samples, and to identify the foreign substance in the contaminated soil sample. Experimental Procedure
First, determine the dry weight of the soil by removing it's moisture content. Do this by placing samples of both soil samples on separate watch glasses and oven dry both for one week. After the week, take the samples out and weigh them. compare this to the "wet" weight to find the percent of moisture content in each sample.
Second, measure the pH of each using a pH probe . It is difficult to use on a dry soil sample so make a suspension of each soil sample by mixing 10 grams of dry soil with approximately 20 mL of deionized water. Using this suspension determine the pH of each soil sample. Make sure to calibrate the pH probe before measuring the sample's pH.
Next, determine the buffering capacities of both of the soil samples. To test this, make several solutions of each soil (each with about .5 gram of soil) with .1 M KCl as the solvent and varying amounts of .1 M HCl (use deionized water to make the solutions even. Do not change amount of KCl.). Allow the samples to equilibrate and then determine the pH using a pH probe.
To determine the amount of Calcium Carbonate (CaCO3), add hydrochloric acid to the samples. Mix 1 gram of dry soil with 10 mL of 1 M HCl. After this add 10o mL of deionized water and 3 drops of phenothalein and mix the contents together. Titrate the solution with 1 M NaOH. calculate the amount of NaOH used to titrate the samples to determine the amount of calcium carbonate, If there is a significant ammount in the soil it may "fizz" when adding the HCl.
In order to determine the amount of chloride ion present in the soil samples, use a chloride selective electrode in a solution of the soil. Weight 5 grams of each soil sample and add a 100 mL of deionized water to form the solution for each sample. Next prepare 120 mL of .01 M, .001 M, and .0001 M solutions of .1 M NaCl by serial dilution. Use the electrode to measure the voltage of each serial dilution and the soil samples.
To find out whether sodium, potassium, or magnesium ions are present in the soil use a flame test. Get a flat wooden stick and cover it in deionized water . After this cover it in one of the soil samples and hold over a lit Bunsen burner. Be sure not to hold in the flame for too long or the stick will catch fire. The color the flame turns will show what ion is present in your soil (sodium will turn, potassium will have a blue flame, have a violet flame, and Magnesium may not burn or it may a have an orange flame).
Results and Discussions
Cited: 1. Campbell N.A.; Reece J. B. In Biology; Wilbur, B., Ed.; Biology 8th edition; Pearson Benjamin Cumming: San Francisco, CA, 2008; 1. pp 786-787
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