Materials and Supplies Needed

Metal or plastic cylinders (30 cm long, 15 cm diameter) with one end beveled for ease in insertion into soil

Plastic lids to seal the cylinders, available from Sinclair & Rush, Inc., St. Louis, MO

Aluminum foil, to cover cylinders and lids, to minimize any heat loading

Screw-capped glass jars (4-6 cm diameter, 7-8 cm high) Tripods made of metal or plastic NaOH solution (0.5 or 1.0M) Barium chloride solution (1.0 M)

HCl solution, or definitive (determined) molarity, ideally 1.0 M Thymolphthalein indicator: 1 gram (g) thymolphthalein is dissolved in 100 milliliters (mL) 95% ethanol. (Other references [e.g., Alef and Nannipieri, 1995] describe the more often used phenolphthalein, but it has a less-definitive end point, changing from dark to light pink at the end point. In contrast, the thymolphthalein changes from blue to colorless at the end point very rapidly, which gives the definitive end point so desired in this titration.)

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