(1) In a 5-square enameled kettle, 1587 kg of water, 1032 kg of fumaric acid, and 352 kg of ammonium bicarbonate were added sequentially and stirred uniformly;
(2) it was kept warm at 50 C., and stirred at 22 rpm for 10 h, to obtain iminodiacethanedisuccinic acid solution;
(3) to the iminodiacethanedisuccinic acid solution, 32% (mass concentration) of liquid base was added 2225 kg to obtain 5000 kg of 30% (mass concentration) tetrasodium iminodisuccinate solution. The final tetrasodium iminodisuccinate solid obtained after removal of water was 98% pure and contained 1% unreacted fumaric acid and 1% malic acid.
