Argon
2 of the 6 encyclopedias on this shelf carry an entry for Argon. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
ar'gon, an element in the air discovered in 1894 by Professors Strutt (Lord Rayleigh) and Ramsay of England. A hundred years earlier Cavendish suggested the existence of such a gas. The discoverers of argon were led to the new element-by noticing that nitrogen obtained from air was always heavier by one-half of one per cent than that prepared from compounds. Investigation proved that atmospheric nitrogen had mixed with it an element new to science. On further investigation of argon obtained from liquid air , it has been found that argon is associated with minute quantities of yet other unsuspected elements. Under ordinary conditions, argon is an odorless, tasteless, colorless gas. Argon liquefies under a pressure of 40 atmospheres at a temperature of -184 degree F., and freezes at -310 degree F. As a liquid it is denser than water. Little is known of argon's chemical properties save that it is inert and does not combine with any other element. The name is Greek and signifies inactive. See Air
Collier's New Encyclopedia (1921)
a constituent gaseous element discovered in our atmosphere by Lord Rayleigh and Prof. Ramsay, in 1894. Argon has a characteristic spectrum. Its specific gravity (H=l) is between 19 and 21. It is about 2½ times as soluble in water as nitrogen. Its critical temperature (-121°C.) and boiling point (-187°C.) are lower than those of oxygen. It seems to be incapable of combining with anything. It has been found in cleveite and in a meteorite. There is still much doubt concerning its true status. It is separated by acting on air with red-hot copper filings to separate the oxygen. The residual gas is dried and passed over white-hot magnesium filings. The magnesium combines with the nitrogen, producing a solid nitride and leaving argon as a gas.
What Has Changed in the Last Century
Collier's admitted in 1921 that "there is still much doubt concerning its true status" — argon's odd position was only settled once Moseley's atomic numbers and the quantum picture of electron shells explained it as element 18 with a filled outer shell, the anchor of the noble-gas group that Aiton's 1910 entry could already see filling up with neon and helium. Both accounts call the gas incapable of combining with anything; that held for over a century until a team in Helsinki made argon fluorohydride (HArF) in 2000, stable only at temperatures near those at which Aiton's liquid argon existed. The laborious red-hot copper and white-hot magnesium method Collier's describes has been replaced by fractional distillation of liquid air, which yields argon by the hundreds of thousands of tons a year for welding shields, double-glazed windows and metallurgy. One use the old writers could not have guessed: the steady decay of potassium-40 into argon-40 became the basis of potassium-argon dating, which from the 1950s put ages on volcanic rocks and on the sediments holding early human fossils.
Written for this edition, 2026.