The present invention relates to a chelating agent precursor that contains glutamic acid N,N-diacetic acid (GLDA) and/or methylglycine N,N-diacetic acid (MGDA) wherein at least one of the carboxylic acid groups is present as a carboxylic acid derivative selected from the group of amides, anhydrides, and esters, combinations thereof, and salts thereof, provided that it is not the triethyl ester of GLDA, the triethyl mono-t-butyl ester of GLDA, the tri-t-butyl ester of GLDA, the monobenzyl tri-t-butyl ester of GLDA, any ester or amide that contains azacycloalkane groups, any amide that contains biotin groups, any amide that contains minoethylcarbamoyl based amide groups, (S)-diethyl 2,2′-(1-benzyloxy)-1,5-dioxo-5-(prop-2-ynylamino)pentan-2-ylazanediyl-diacetate, diethyl 2,2′-(5-(3-azidopropylamino)-1-(benzyloxy)-1,5-dioxo-pentan-2-ylazanediyl-diacetate, the trimethyl ester of MGDA, the monomethyl ester dimethylamide of MGDA, the dibenzyl ester of MGDA, the dibenzyl mono t-butyl ester of MGDA, the di t-butyl ester of MGDA, the di-t-butyl-monobenzyl ester of MGDA, N,N-bis(benzyloxycarbonylmethyl)-N′-methoxycarbonyl-methyl-alanine amide, or N,N-bis(tert-butoxycarbonyl)-N′-methoxycarbonylmethyl-alanine amide, and esters of GLDA immobilized on a gel, and that the amide is not the amide of ammonia, to a fluid containing the above chelating precursor and a liquid, and to the use of a chelating agent precursor of MGDA and GLDA and fluids containing them in an application wherein delayed acidity or the chelating capacity is useful, such as in descaling, bleaching, cleaning, and treating oil and/or gas-containing subterranean formations.