EXTRACTION OF SODIUM FROM THE SURFACE OF GLASS BY THE PRODUCTS OF DECOMPOSITION OF AMMONIUM-SULFATE

Extraction of sodium from the surface of container glass was studied f or temperatures of 400 degrees C and 600 degrees C in terms of the tim e of heating (exposure) and the way of dosing (single dose and repeate d doses) of ammonium sulphate. The amount of sodium extracted increase s with increasing temperature of heating. At the lower dealkalization temperature, the time dependence exhibits a steady increase in the amo unt of sodium extracted with both the single a repeated dosage of the reactive agent, ana shows a parabolic course. At the higher temperatur e, the amount of sodium extracted increases uniformly only when the de alkalizing agent is supplied continuously to the glass surface (repeat ed dosing). The chemical durability of all the dealkalized surfaces is many times higher than that of the original untreated glass. Ita the case of glass surface dealkalized at the higher temperature with on on ly limited dose of the reactive agent, the chemical durability of the surface is becoming gradually reduced as a result of the diffusion of sodium from the internal glass layers into the dealkalized surface lay er.