Ferricyanide Crystal

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Structure

The structure of potassium ferricyanide

The structure of potassium ferricyanide consists of an iron molecule octahedrally coordinated by six cyanide ligands.

General Information

• Molecular Weight: 329.24 g/mol
• Appearancy: Red crystalline solid
• Melting Point: 300°C
• Density: 1.89 g/cm³
• Crystal Structure:Monoclinic

Safety

• When exposed to HCl, potassium ferricyanide forms hydrogen cyanide gas which is an asphyxiant and can be fatal.
• Potassium ferricyanide is not very toxic, but can stain.

General Procedure

A picture of the potassium ferricyanide crystal grown by Seth Croslow

The most general way to grow a crystal includes forming a supersaturated solution by heating up water and adding in the crystal medium, here I used Potassium Ferricyanide, until is doesn't dissolve anymore.

For a general procedure, the following link can be used: How to Grow a Potassium Ferricyanide Crystal

The following is the procedure that I followed:

1. Obtain potassium ferricyanide, a 250 mL beaker, a stirplate/hotplate, and a stirbar.
2. Begin heating up the water on the hotplate and add the stirbar.
3. Once hot, begin adding the potassium ferricyanide (It will take some time for it to dissolve, but it eventually will).
4. Keep adding until the rate of dissolution decreases( The article above mentions to use about 93g in 200mL of water).
5. Cover the finished solution with something(a watchglass or parafilm) and let it sit overnight.

Note: Another way to do this would be to make a saturated solution and allow the water to evaporate slowly over time. This may yield a single large crystal instead of a conglomerate of smaller crystals, although it will take significantly longer.