Abstract: The invention relates to a polymeric indicator fixed in a polymeric gel carrier, wherein the polymeric gel carrier comprises a hydrophilic polymer, wherein the polymeric indicator and the hydrophilic polymer are present together in the form of a combined cross-linked hydrogel network fixed by chemical bonds. The invention further relates to a method for preparing a polymeric indicator fixed in a polymeric gel carrier and to a sensor for measuring pH, which comprises the polymeric indicator fixed in a polymeric gel carrier.

Abstract: Flue gases from a glass-melting furnace, after passing through an elevated recuperator, descend through a vertical cooling column into a horizontal convective boiler before being exhausted into a smokestack. Entering water, circulating essentially in counterflow to the flue gases, is preheated in an exit compartment of the boiler and passes via a flow regulator into the main boiler chamber and thence into a bank of vertical pipes on the periphery of the column. On rising through these pipes, the water is partly converted to steam which is superheated in an entrance compartment of the boiler before being fed to a load, the remaining water being returned to the boiler chamber.