I use ferrous chloride as a highly selective nitro-group reducing agent in the preparation of aromatic amino acids. I have given up trying to preserve
it in any form and now prepare it immedately prior to use by passing a solution of ferric chloride in hydrochloric acid slowly through steel wool and
filtering off the excess wool and black residue. Ferrous sulphate is definitely more stable but the sulphate ions left in solution after the reduction
complicate the work up. |