Verification of iron(III) with potassium cyanide

Attention: Inasmuch as the orginally used cyanide was most likely cyanate, false results were obtained. The experiment was repeated with authentic cyanide, and the test procedure, elucidation and photos were corrected. Even if this error fortunately caused no endangerment, still my apologies for this mistake!

Chemicals needed

distilled water

Potassium cyanide solution, diluted T+ R 26/27/28-32 S (1-2)-7-28-29-45

Iron(III) chloride solution Xn R 22-38-41 S 26-39

Equipment needed

test tube

Test procedure

The use of cyanides presupposes a very thorough knowledge concerning its hazardous properties! Every exposition is to strictly avoided!
One adds to a test tube about 1 ml water and adds 2-3 drops of iron(III) chloride solution. The solution becomes slighty yellow in color.
Now one adds 4-5 drops of diluted potassium cyanide solution. ~~The yellow color becomes noticeably deeper and somewhat turbid.~~ A deep blue precipitation takes place.

Disposal

One adds a surplus of iron(III) chloride solution, in order to complex the cyanide completely. One can then discharge the solution into the drainage and one rinses thoroughly with water.

Elucidation

Iron(III) chloride reacts with potassium cyanide to form the complex ~~potassium hexacyanoferrate(III) (red prussiate of potash)~~ iron-hexacyanoferrate (III) (Prussian blue). One can with this method verify cyanide. Furthermore the formation of this complex is, because of its rather high level of stability, a useful way to render cyanide harmless.

~~FeCl3 + 6 KCN --> K3[Fe(CN)6] + 3 KCl~~

2 FeCl3 + 6 KCN --> Fe3[Fe(CN)6] + 6 KCl

Photos

Literature

of own device