The present invention relates to an alkaline earth metal salt or an organic amine salt of a compound represented by the formula [I]: wherein R.sup.1 and R.sup.2 are each a hydrogen atom, a halogen atom, or an optionally substituted linear hydrocarbon group; ring A is an optionally further substituted benzene ring; B is an optionally substituted benzene ring; R is a carboxyl group or a linear hydrocarbon group substituted with a carboxyl group and the like. ##STR00001##