Haemoglobin is an essential component of the blood. The central, active part of the molecule comprises a haem ring (as above) at the centre of which lies an iron ion.
We call it a charge transfer couple, since it requires two constituents, both the iron and the haem.
An old-fashioned way of removing the stain caused by blood is to place the stained item in a fairly concentrated solution of salt, and is usually performed by sprinkling table salt on the bloodied cloth after dampening it under a tap ......
Give reason for :Table salt is used to remove blood stains