Toughened Glass

Abstract

THE night before last a lady of my family emptied a paper powder composed of 71/2 grains of carbonate of potash and 71/2 grains of carbonate of soda into a tumbler of what is called toughened glass less than half full of cold water. After stirring the mixture she drank the contents, leaving a silver tea-spoon in the tumbler, and then placed the empty tumbler on the table by her side within perhaps a foot of a burning duplex lamp. About five minutes afterwards a sharp explosion occurred, which startled all in the room. We found the tumbler shattered into fragments, the body of the glass ripped up, as it were, into several large, irregular-curved pieces, and the bottom of the tumbler broken into small pieces more resembling thick rough ice than anything else. Query: Was the explosion caused by the inherent properties of the toughened glass, or by the contact of potash, soda, the silver spoon, and proximity to a lamp, the heat from which was very slight, indeed scarcely perceptible to the hand at the spot where the tumbler stood?