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How to Remove Nitrates From Solids

Nitrates are salts of nitric acid --- compounds that include the nitrate ion, NO3 with a -1 charge. They dissolve well in water, so the easiest way to separate them from a mixture of other insoluble solids is by dissolving the mixture in water and then filtering it to separate solution from insoluble material. This easy approach can make for a simple experiment in a classroom or lab.

Things You'll Need

Lab coat, goggles and gloves (make sure you have these on)
3 beakers
Spatula
Deionized water
Graduated cylinder
Mortar and pestle
Hot plate
2 vacuum hoses
2 sidearm filter flasks
Vacuum adapter
2 ring stands
2 clamps
Buchner funnel
Filter paper
Pasteur pipette
Glass stir rod

Instructions

- 1
  Add the sample you want to separate to a beaker using a spatula. If necessary, grind it up with a mortar and pestle first.
- 2
  Add some water --- about 25 mL or so --- to the second beaker and place it on the hot plate. Heat it to a gentle boil.
- 3
  Set up the vacuum filter system in the meantime. Clamp the two sidearm filter flasks to the two ring stands. Feed the first vacuum hose from the vacuum outlet on your lab bench to the first sidearm flask, and use the vacuum adapter to connect it. Feed the second vacuum hose from the first sidearm flask to the second, attaching it to each using the side arms. Finally, place the Buchner funnel in the mouth of the second sidearm flask and line it with a sheet of filter paper.
- 4
  Pour some of the hot water onto your solid sample and stir with a glass rod to mix. Turn on the vacuum.
- 5
  Dampen the filter paper in the funnel with a little water using your Pasteur pipette. Transfer the liquid from your beaker into the funnel with the pipette. Then wash the solids in the beaker with a little more hot water and pour it in, rinsing the beaker with the hot water to flush all the remaining solids into the funnel.
- 6
  Turn off the hot plate. Rinse the contents of the funnel with some more hot water to remove any more soluble nitrate.
- 7
  Turn off the vacuum. Carefully remove the filter paper from the funnel and scrape its contents into the third beaker. Allow it to dry overnight, preferably in a desiccator.

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