Abstract: A water-soluble ampholyte which comprises the reaction product between(a) one or more compounds selected from the group comprising certain amino-acids, hydroxylamine, an amine of the formula ##STR1## wherein R.sub.1 is hydrogen, the group H.sub.2 N--(CH.sub.2).sub.n --, wherein n is an integer 2-6, or the group H.sub.2 N--(CH.sub.2).sub.3 --NH--(CH.sub.2).sub.3 --, R.sub.2 and R.sub.3 are the same or different and each representing hydrogen, methyl, ethyl or hydroxyethyl or together with the intermediate nitrogen atom form certain heterocyclic groups, and certain di- and tripeptides, at least one of these compounds being one which contains at least one carboxyl group, or salts of the aforementioned compounds, and(b) at least one bifunctional alkylating agent containing a straight or branched alkylene chain having 2-10 carbon atoms and which chain may be substituted with certain substituents and/or be broken by 1-3 oxygen atoms with certain conditions, in a molar relationship between (b) and (a) of 1:2-9:10.