Question

what is the chemical present in ink

Answer 1

here is your answer friend
iron sulphate and Gallic and tannic acid present in ink

Answer 2

Ink pigments are both inorganic and organic. Most red writing inks are a dilute solution of the red dye eosin. Blue colour can be obtained with substituted triphenylmethane dyes. Many permanent writing inks contain iron sulfate and gallic and tannic acids as well as dyes