\Eu`di*om"e*ter\, n. [Gr. ? fair, clear weather, fr.
? fine, clear ( said of the air or weather) + -meter: cf. F.
ediom[`e]tre.] (Chem.)
An instrument for the volumetric measurement of gases; -- so
named because frequently used to determine the purity of the
air.
Note: It usually consists of a finely graduated and
      calibrated glass tube, open at one end, the bottom; and
      having near the top a pair of platinum wires fused in,
      to allow the passage of an electric spark, as the
      process involves the explosion and combustion of one of
      the ingredients to be determined. The operation is
      conducted in a trough of mercury, or sometimes over
      water. Cf. {Burette}. Ure's eudiometer has the tube
      bent in the form of the letter. U.