The Collaborative International Dictionary of English v.0.48:

Natron \Na"tron\, n. [F., fr. Sp. natron, Ar. natr[=u]n,
   nitr[=u]n. Cf. Niter, Anatron.] (Min.)
   Native sodium carbonate. [Written also anatron.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Anatron \An"a*tron\, n. [F. anatron, natron, Sp. anatron,
   natron, fr. Ar. al-natr[=u]n. See Natron, Niter.] [Obs.]
   1. Native carbonate of soda; natron.
      [1913 Webster]

   2. Glass gall or sandiver.
      [1913 Webster]

   3. Saltpeter. --Coxe. --Johnson.
      [1913 Webster] Anatropal