PROCEDURES

On the data sheet (pg. 18-7) record your observations concerning the color and crystalline form of the salt. Also record your observations concerning the solubility of the salt in water. If the salt is water soluble, record the color of the solution. Also use a stirring rod to place a drop of solution on red and blue litmus. This will help you determine the pH range of the solution, which in turn will give some insight into the character of the salt. Remember that the salts of weak acids tend to be basic and the salts of weak bases tend to be acidic. You may also wish to review the fact that metal ions with a high charge and a small size tend to produce acidic solutions.

To proceed with the analysis for the cation, test for the presence of NH₄⁺ first. Do the ammonium test normally except that instead of using solution, add a few granules of the solid unknown to the 50% NaOH. A positive test means that you have found your cation. If it is not positive, add a quantity of the salt about the size of a grain of uncooked rice to about 1 mL (20 drops) distilled water. Use this solution and start your analysis with the "Precipitation of Group III" on Page 16-7. Continue the analysis until you have a positive confirmation test for one of the cations in your qualitative analysis scheme.

After the identification of the cation, proceed with the identification of the anion. Perform the elimination tests first. If the cation is colored, this may alter slightly the observation of the color of solutions and precipitates formed but will not affect the color of gases generated. You may find that you will need to centrifuge and decant in order to observe the color of precipitates accurately. If you have questions, ask your instructor. After performing the elimination tests, perform the necessary confirmation tests to identify positively the anion of your salt.

If your cation is colored and your anion is a Group II halide, Cl^-, Br^-, or I^-, after treating with hydrogen peroxide and extracting with toluene, you may need to use a medicine dropper to remove the colored, lower aqueous solution and replace it with distilled water. This will facilitate accurate identification of the halide anion present. The test, however, is usually definitive without this process. Again, ask your instructor for information if you have questions.

If nitrate ion is the suspected anion, addition of FeSO₄ in the brown ring test may result in a precipitate. If a precipitate forms, centrifuge and decant, saving the decantate. Perform the brown ring test on the decantate.

Record all observations made in the analysis of your salt for the cation and the anion on the data sheet. Write NET IONIC EQUATIONS for ALL reactions for the cation and anion of your salt. Check the results of your analyses by reporting the formula of your salt (appropriate space on Page 18-7) to your instructor. Also complete the conclusion section.

The Environmental Protection Agency (EPA) is a governmental body that investigates reported and observed violations of the rules protecting our land, water and air. Ninety-eight percent of the companies in the United States abide by the rules in the day to day operation of their business. Occasionally accidents or spills occur and the EPA is called in to determine whether laws have been broken and if so what fines should be assessed.

As the local EPA agent, you have been called to Tarboro, NC at 3:00 a.m. to take charge of the clean-up operation after a freight train jumped the track and caught fire. When you arrive at the scene you observe that several box cars have split open and a tank car is leaking and this tank car is the source of the fire. Firemen on the scene have built a dike around the tank car which contains kerosene and have the fire under control. A box car shipped from Monroe Chemicals has split open and all the drums of chemicals are falling out. Before the fire was brought under control it had scorched or burnt the labels on most of the drums. Further inspection reveals that one of the drums has split open and is spilling its crystalline contents into the adjacent creek. You are aware that the creek leads into the Tar River just around the next bend and that ten miles downriver Greenville has the intake for its city water supply. You arrange to have a dike built around the leaking drum and you obtain a sample of the crystalline contents of the drum.

Your present concern is for the people of Greenville. You must quickly analyze the sample and report your analysis to the Greenville Water Department so they can begin testing the river water to determine whether the contaminate has reached them and if so whether it represents a danger to the town. Small amounts of the anions in your qualitative analysis scheme can be tolerated, but of the cations only Fe²⁺, Fe³⁺, NH₄⁺, and Ca²⁺ are considered safe. On your report sheet indicate whether you think the compound you found poses a sufficient health hazard for the city of Greenville to close their water intake.