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How To Grow Ammonium Phosphate Crystals

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This single crystal of ammonium phosphate grew overnight.

This single crystal of ammonium phosphate grew overnight. The green-tinted crystal resembles an emerald. Ammonium phosphate is the chemical most commonly found in crystal growing kits.

Anne Helmenstine

Monoammonium phosphate is one of the chemicals included in commercial crystal growing kits because it is safe and practically foolproof for producing a mass of crystals quickly. The pure chemical yields clear crystals, but you can add food coloring to get any color you desire.

Difficulty: Easy

Time Required: one day

Here's How:

  1. Stir six tablespoons of monoammonium phosphate into 1/2 cup of very hot water in a clear container. I use water heated from an electric drip coffee maker and a drinking glass (which I wash before using it again for beverages).
  2. Add food coloring, if desired.
  3. Stir until the powder is completely dissolved. Set the container in a location where it won't be disturbed.
  4. Within a day, you'll have a bed of long, thin crystals blanketing the bottom of the glass or else a few large single crystals. Which type of crystals you get depend on the rate at which the solution cools. For large single crystals, try to cool the solution slowly from very hot down to room temperature.
  5. If you get a mass of crystals and wanted one big crystal, you can take a small single crystal and place it in the growing solution (either new solution or the old solution that has been cleared of crystals) and use this 'seed crystal' to grow a large single crystal.

Tips:

  1. If your powder doesn't completely dissolve, it means your water probably should have been hotter. It's not the end of the world to have undissolved material with these crystals, but if it concerns you, heat the solution in a microwave or on the stove, stirring occasionally, until it's clear.
  2. Monoammonium phosphate, NH4•H2PO4, crystallizes in quadratic prisms. The chemical is used in animal feed, plant fertilizers, and is found in some dry chemical fire extinguishers.
  3. This chemical may cause irritation and itching. If you spill it on your skin, wash it off with water. Inhaling the powder may lead to coughing and a sore throat. Monoammomium phosphate is not toxic, but it's not exactly edible.

What You Need:

  • monoammonium phosphate
  • hot water
  • clear container

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