Abstract: Polymeric color pH indicators are prepared which are insoluble in the measured aqueous medium and show a certain range of color change. These polymeric indicators are the product of copolymerization of a hydrophilic comonomer, selected from esters, amides and N-substituted amides of acrylic and methacrylic acid, with 0.1- 30 wt.% of a comonomer. The comonomer forms the pH-indicating color center by a subsequent coupling with a suitable diazonium salt or a passive component. Vinylic monomers comprising an aromatic system in the molecule are suitable as the functional comonomers. The indicators are prepared by radical copolymerization of the comonomers either in a suspension or in a solution, followed by the subsequent coupling with a diazonium compound, or diazotizing and coupling with a passive component, to obtain the pH-indicating sites of polymer.

Abstract: The invention relates to biologically active insoluble compounds on a carrier containing in its side chains a p-phenylene-diamine skeleton, where a polymer of the general formula I ##STR1## where R.sub.1 is a polymer residue, R.sub.2 is a lower alkyl group, x = 1-4, is oxidized in the presence of a soluble biologically active compound containing a primary amino group, such as e.g. enzymes, coenzymes, inhibitors of enzymes, hormones, or antigens. The oxidation is carried out by using an oxidation agent which does not disturb the biologically active compounds present in the mixture.