which was maintained at that temperature a mixture of about 20 l h sulphur dioxide and 1000 l h air was fed to the chamber through inlet ducts which contained vanadium pentoxide as catalyst to promote oxidation of the sulphur dioxide and in excess of 90 of the sulphur dioxide was in fact oxidised the glass remained in that chamber for a period in excess of 1 minute and was then transferred to the second chamber 7 which was maintained at a temperature of 340 u00b0 c a mixture of between 50 and 60 l h sulphur dioxide and between 1000 and 2000 l h air was fed to that second chamber the glass was exposed to the dealkalising media in the two chambers for a total period in excess of ten minutes the thus dealkalised glass was then subjected to the haze and lixiviation tests specified in example 1 and the results were compared with those given by a specimen of glass of the same composition which was untreated in the haze test the untreated soda lime glass exhibited iridescence after 2 to 3 days the specimen of dealkalised glass did not exhibit iridescence before about 19 days had passed in the lixiviation test it was found that more than 5 mg sodium was extracted from the untreated.