Use of glycine-N,N-diacetic acid derivs. of formula (I) is claimed as complex formers for alkaline earth or heavy metals. R = 1-20C alkyl, 2-20C alkenyl or -A.CH(COOM).N(CH2COOM)2; A = 1-12C alkylene or a chemical bond; M = H, alkali metal or opt. substd. ammonium. The use of ~a-alanine-N,N-diacetic acids as builders in textile-washing powders or as Ca sequestrants in oral hygiene compsns. is specifically excluded. Also claimed are 2-alkylglycine-N,N-diacetonitriles or 2-alkylglycinenitrile -N,N-diacetonitriles (where alkyl = 1-20C alkyl or 2-20 C alkenyl); and cpds. of formula (II). X = carboxylic acid or nitrile function. Cpds. of formula (I) are new except when R = 1-3C alkyl and A = chemical bond.