The Origin of the Word "Mole"

The following article mentions the origin of the word mole, quoting from the original documents:

"Mole and Chemical Amount: A Discussion of the Fundamental Measurements of Chemistry" by George Gorin (Journal of Chemical Education, vol. 71 No. 2, p. 114-116, Feb. 1994)

On p. 116, Gorin writes:

The unit "mole" was introduced into chemistry around 1900 by Ostwald, and he originally defined this unit in terms of gram. Gram is a unit of mass; but what is the mole a unit of? Ostwald did not say;3 however, several years later, he did make it clear that the concept of mole should be linked to the ideal gas. 4

3"...the molecular weight of a substance, expressed in grams, shall henceforth be called mole [. . . das in Grammen augedruckte [. . .] Molekulargewicht eines Stoffes soll fortan ein Mol heissen]" Ref. 7).

4 "That amount of any gas that occupies a volume of 22414 mL in normal conditions is called one mole [eine solche Menge irgendeines Gases, welche das Volum von 22412 ccm im Normalzustand einnimt nennt man ein Mol]" (Ref. 8)

Ref. 7. Ostwald, W. Grundriss der allgemeinen Chemie; Leipzig: Engelmann, 1900, p. 11

Ref. 8. Ostwald, W. Grundriss der allgemeinen Chemie, 5th ed.; Dresden: Steinkopff, 1917, p. 44

The Oxford English Dictionary has the following:

Mole .... Also mol (formerly a an alternative spelling, now usd as an abbrev.). [a. G. mol (W. Ostwand "Grundlinien d. anorg. Chem." (1900) viii. 163), f. mol-ekul MOLECULE.] That amount ....

The first use listed is:

1902 A. Findlay tr. Ostwald's "Princ. Inorg. Chem." viii. 156 When one gram-molecular or one mole (the molar or molecular weight of a substance expressed in grams) of any substance is dissolved in a liter or 1000 gm. of water, the solution produced freezes at -1.850 degrees....

The OED indicates an earlier use of the term "gramme molecule." Under Molecule:

1878 A. Crum Brown in Encycl. Brit. XVI. 621/1 Whe a chemist speaks of acting on a molecule of succinic acid with two molecules of pentachloride of phosphorus, he means that he mixes them in the proportion of 118 parts of the former to 2 x 117.5 of the latter. For the sake of precision we sometimes speak of a molecule of water (or other substance) in grammes, or even of a gramme molecule, a grain-molecule, &c. Return to Mole Menu