Basic Chemistry of Cyanotyping (1)
When iron ( Fe, from the Latin "Ferrum") is chemically combined with other elements, its atoms acquire a positive charge by transferring two or three of their orbiting negative electrons onto atoms of other elements. So each iron atom ends up in one of two states: "ferrous" iron - also called
iron (II) or Fe2+ for short, "ferric" iron - also called iron (III) or
Fe3+. This number 2+ or 3+ is called the oxidation state of the iron, and signifies the positive electric charge that the iron atom has acquired in the
reaction.
Oxidation makes an atom or molecule more positive (or less negative) in the electrical sense. So when iron forms compounds, it is oxidized. Reduction is the converse: making an atom or molecule less positive (or more negative). e.g. oxygen gas, which consists of molecules containing two linked atoms of oxygen,
O2, is reduced to form oxides, which contain the O2- ion.
Both processes involve the transfer of electrons. Oxidation is the removal of electrons while reduction is their addition.