Carbonic Acid
2 of the 7 encyclopedias on this shelf carry an entry for Carbonic Acid. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
more properly called CARBONIC ANHYDRIDE, or CAR- BON DIOXIDE, a gaseous compound of 12 parts by weight of carbon and 32 of oxygen, colorless, without smell, 22 times as heavy as hydrogen, turning blue litmus slightly red, and existing in the atmosphere to the extent of 1 volume in 2,500. It is incapable of supporting combustion or animal life, acting as a narcotic poison when present in the air to the extent of only 4 or 5 per cent. It is disengaged from fermenting liquors and from decomposing vegetable and animal substances, and is largely evolved from fissures in the earth, constituting the choke-damp of mines. From its weight it has a tendency to subside into low places, vaults and wells, rendering some low-lying places uninhabitable. It has a pleasant, acidulous, pungent taste, and aerated beverages of all kinds-beer, champagne, and carbonated mineral water-owe their refreshing qualities to its presence, for though poisonous when taken into the lungs, it is agreeable when taken into the stomach. This acid is formed and given out during the respiration of animals, and in all ordinary combustions, from the oxidation of carbon in the fuel. It exists in large quantity in all limestones and marbles. It is evolved from the colored parts of the flowers of plants both by night and day, and from the green parts of plants during the night. During the day plants absorb it from the atmosphere through their leaves, and it forms an important part of their nourishment.
The Encyclopedia of Founding (1892)
This acid is composed of oxygen 72, carbon 28; specific gr. 1.529, air being 1.000. All forms of carbon when burned in the air unite with oxygen to form carbonic acid. It constitutes 44 per cent of limestone. A cubic inch of marble yields four gallons of the gas. Under a pressure of 36 atmospheres at 32 deg. carbonic acid shrinks into a colorless liquid lighter than water. It does not resume the gaseous state when the pressure is removed, but evaporates with great rapidity, one portion absorbing heat from another, and thus freezing it into a white substance like snow. Unlike other acids, it does not unite with water to form a definite hydrate. It is anhydrous in all the three states--gaseous, liquid, and solid. It is incombustible, and a non-supporter of combustion. See GASES; LIQUID; SOLID.