Materials: Glass
Chemical resistance

Chemical interaction of glass with water and acids
The chemical interaction of water and acids with glass surfaces is negligibly small; only very small amounts, primarily mono-valent ions, are dissolved from the glass. This forms a very thin, almost non-porous layer of silica gel on the glass surface, inhibiting further attack. Exceptions are hydrofluoric acid and hot phosphoric acid which prevent the formation of the inert layer.

Chemical interaction of glass with alkalis
Alkalis attack glass surfaces as concentration and temperatures increase. Borosilicate glass 3.3 limits surface erosion to the μm range; however, after prolonged exposure, volume changes and/or graduation destruction may occur.

 

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Water resistance of glass grains 
DURAN® meets hydrolytic resistance class 1 of DIN ISO 719 (98 °C), which is divided into 5 hydrolytical resistance classes. This means that when glass grain with a granulation rate of 300-500 μm is exposed to water at 98 °C for 1 hour, less than 31 μg Na2O per gram of glass grain will be removed. In addition, DURAN® also meets class 1 of DIN ISO 720 (121 °C), which is divided into 3 hydrolytical resistance classes. This means that when glass grain is exposed to water at 121 °C for 1 hour, less than 62 μg Na2O per gram of glass grain will be removed.

Acid resistance
DURAN® meets class 1 of DIN 12 116, which is divided into 4 acid resistance classes. DURAN® is also called acid-resistant borosilicate glass, as the surface erosion after 6 hours of boiling in 6 N HCl is less than 0.7 mg/100 cm2. Removal of alkali oxide according to DIN ISO 1776 is less than 100 μg Na2O/100 cm2.

Alkali resistance
DURAN® meets class 2 of DIN ISO 695, which is divided in 3 alkali resistance classes. Surface erosion after 3 hours of boiling in a mixture with equal volumes of sodium hydroxide solution (1 mol/l) and sodium carbonate solution (0.5 mol/l) is approximately 134 mg/100 cm2.