What is "k4cn6fe"

Ferrocyanide \Fer`ro*cy"a*nide\ (? or ?; 104), n. [Ferro- + cyanide.] (Chem.) One of a series of complex double cyanides of ferrous iron and some other base.

Potassium ferrocyanide (Chem.), yellow prussiate of potash; a tough, yellow, crystalline salt, K4(CN)6Fe, the starting point in the manufacture of almost all cyanogen compounds, and the basis of the ferric ferrocyanate, prussian blue. It is obtained by strongly heating together potash, scrap iron, and animal matter containing nitrogen, as horn, leather, blood, etc., in iron pots.