Natron,

Chambers's Encyclopaedia, Volume 7: Maltebrun to Pearson, p. 407

Natron, or TRONA, an impure sesquicarbonate of soda, which always contains sulphate of soda and chloride of sodium. It is obtained from the margins of lakes in Egypt, Siberia, Tibet, &c., and from the borders of the Black and Caspian Seas.

Source scan(s): p. 0416