1,2,3-Propanetricarboxylic acid, 2-hydroxy-, mixt. with 5-hydroxy-6-methyl-3,4-pyridinedimethanol hydrochloride, 2-hydroxy-1,2,3-propanetricarboxylic acid magnesium salt (1:1), 2-hydroxy-1,2,3-propanetricarboxylic acid tripotassium salt, and 2-hydroxy-1,2,3-propanetricarboxylic acid trisodium salt