Abstract: An aqueous solution of sodium ferrous citrate is obtained by combining sodium hydrogen carbonate with an aqueous solution of iron citrate obtained by stirring and mixing citric acid, water and iron. The amount of citric acid (assumed to have a purity of 100%) per 100 ml of water is from 0.05 g to the dissolution limit amount of citric acid at the water temperature. The amount of iron (assumed to have a purity of 100%) per 100 ml of water is from 10 to 25 parts by mass relative to 100 parts by mass of citric acid. And the amount of sodium hydrogen carbonate (assumed to have a purity of 100%) per 100 ml of water is from 80 to 120 parts by mass relative to 100 parts by mass of citric acid.

Abstract: An iron supply agent includes sodium iron citrate aqueous solution prepared by stirring and mixing citric acid, water and iron combined with sodium bicarbonate, and a chelating agent mixed with the aqueous solution of sodium iron citrate. The chelating agent is lignin sulfonic acid derived from lignin waste water.