water glass

n 1: a glass with the general formula Na2O.xSiO2, x◦3 or 5; used

as a cement or as a protective coating and to preserve

eggs [syn: {soluble glass}, {sodium silicate}]

2: for indicating the level of water in e.g. a tank or boiler

or reservoir [syn: {water gauge}, {water gage}]

3: measures time by the escape of water [syn: {water clock}, {clepsydra}]