Question

Why is ferric chloride preferred over potassium chloride in case of a cut leading to bleeding ?

Answer 1

Ferric chloride results in faster coagulation of blood around the wound , stopping further bleeding . As per Hardy Schuges Law higher the charge on Cation higher will be its capacity to settle the colloids. In case of KCl , K+ is only mono-valent ion hence, less effective . 
Moreover, FeCl3 does not lead to irritation while KCl may lead to severe irritation round the wound.