A. Water (under pressure) absorbs carbonic acid gas; and parts with it (when the pressure is removed) in the form of effervescence.
Q. Why does aerated water effervesce, when the cork is removed?
A. While the cork was fastened down, the water absorbed the carbonic acid; but the moment the pressure is removed (by taking out the cork) the gas is given out with effervescence.
Q. Why does soda water effervesce?
A. Soda water contains 8 times its own bulk of carbonic acid gas, which makes its escape in effervescence, the moment that the cork is removed.
Q. Why does ginger pop fly about in froth, when the string of the cork is cut?
A. All vinous fermentation produces carbonic acid gas. While the cork is fast, the water of the liquor absorbs the carbonic acid; but the moment that the pressure is removed, the gas is given off in effervescence.
Q. Why does bottled ale froth, more than draught ale?
A. Because the pressure is greater in a bottle than in a tub which is perpetually tapped: and effervescence is always produced in proportion to the pressure.
Q. Why does bottled ale and porter become “lively” and frothy by being set before the fire?