Abstract: An antifreeze concentrate for cooling systems in fuel-cell drives which gives ready-to-use aqueous coolant compositions having a conductivity of at most 50 &mgr;S/cm, based on alkylene glycols or derivatives thereof and containing one or more five-membered heterocyclic compounds (azole derivatives) having 2 or 3 hetero atoms from the group consisting of nitrogen and sulfur, which contain no or at most one sulfur atom and which may carry a fused aromatic or saturated six-membered ring.

Abstract: Antifreeze concentrates based on alkylene glycols or derivatives thereof or on glycerol, comprising from 0.0005 to 0.1% by weight of the dye C.I. Reactive Violet 5 (Colour Index No. 18097), based on the total amount of the concentrate.

Abstract: The invention relates to antifreeze concentrates for cooling systems in fuel cell drives, from which are produced ready-to-use aqueous cooling agent compositions having a maximum conductivity of 50 &mgr;m/cm, based on alkylene glycols or the derivatives thereof, and containing orthosilicic acid esters of formula (I) wherein the variables R1 to R4 are the same or different and represent C1-C20 alkyl substituents, C2-C20 alkenyl substituents, C1-C20 hydroxyalkyl substituents, optionally substituted C6-C12 aryl substituents and/or glycol ether substituents of formula (CH2—CH2—O)a—R5 wherein R5 represents hydrogen or C1-C5 alkyl and n represents a number between 1 and 5.