Nitric Acid
2 of the 7 encyclopedias on this shelf carry an entry for Nitric Acid. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
the most important of the five compounds formed by oxygen with nitrogen; symbol HNO3. When pure it is a colorless liquid, very strong and disagreeable to the smell, and so acrid that it cannot be safely tasted without being much diluted. It is known in the arts as "aqua fortis," and is commonly obtained by distilling niter (potassium nitrate) or Chile saltpeter (sodium ni trate) with strong sulphuric Nitric acid contains about 76 per cent. of oxygen, a great part of which it readily gives up to other substances, acting thus as a powerful oxidizer. Thus many metals-such as copper, tin, silver, etc.when brought into contact with this acid are oxidized at the expense of the acid with the production of lower oxides of nitrogen and an oxygenated metallic salt. Nitric acid, when moderately dilute, acts on organic bodies so as to produce a series of most useful substances, notably acetic, oxalic, and picrid acids, isatin or 1878,, white indigo. Nitric acid is employed in ere, etching on steel or copper; as a solvent of for tin to form with that metal a mordant tem- lurgy some and of the finest dyes; in metalwas assaying; also in medicine, in the stitute syphilis a diluted for and state mercurial, as a tonic preparations and as a sub- in Pop. also in form affections of the liver; and of vapor to destroy contagion. Nitric acid is one of the most important essentials in the manufacture of explosives, and thus became of great importance during the World War. Its manufacture through artificial sources was developed in the various countries. The most important of traction of nitrate from the air. See these was the ex- NITRATE.
The Encyclopedia of Founding (1892)
The two principal constituent parts of our atmosphere--oxygen and nitrogen gases--when in certain proportions are capable under particular circumstances of combining chemically into one of the most powerful acids--the nitric. For all practical purposes, nitric acid is obtained from nitrate of potash, from which it is expelled by sulphuric acid. The nitric acid is of considerable use in the arts. It is employed for etching on copper; as a solvent of tin to form with that metal a mordant for some of the finest dyes; in metallurgy and assaying, in various chemical processes, on account of the facility with which it parts with oxygen and dissolves metals. For the purposes of the arts it is commonly used in a diluted state and adulterated with sulphuric and muriatic acids, by the name of aquafortis. Two kinds are made: one called double aquafortis, which is one half the strength of nitric acid; the other simply aquafortis, which is half the strength of the double. A compound made by mixing two parts of the nitric acid with one of muriatic, known formerly by the name of aqua regia, and now by that of nitro-muriatic acid, has the property of dissolving gold and platina. On mixing the two acids heat is given out, an effervescence takes place, and the mixture acquires an orange color. See AQUA REGIA; ATMOSPHERE.