Soda locomotive

Soda locomotives were a variant of fireless locomotives, in which steam was raised in a boiler, expanded through cylinders in the usual way, and then condensed in a tank of caustic soda that surrounded the boiler.

Dissolving water in caustic soda liberated heat, which generated more steam from the boiler, until the caustic soda became too dilute to release heat at a useful temperature.

The boiler was jacketed by a container loaded with about 5 tons of caustic soda (sodium hydroxide).

Steam emanating from the boiler would be fed through pistons to propel the locomotive forward, and the exhaust steam from the pistons would be fed into the caustic soda to continue the cycle.

For reconcentrating, the caustic soda was either transferred out of the boiler of the locomotive and boiled in open vats, or, rather more conveniently, by injecting superheated steam at a high enough temperature to boil off the water in solution.