Soda locomotive
{{Short description|Fireless locomotive}}
{{refimprove|date=January 2016}}
File:Minneapolis, Lyndale, and Minnetonka Railway 'soda motor'.jpg]]
File:Natronbahn.jpg, Germany, 1884]]
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.
Technical description
These closed-loop steam engines had no firebox. The boiler was jacketed by a container loaded with about 5 tons of caustic soda (sodium hydroxide). When water or steam came in contact with the caustic soda, it would generate heat—enough to actually run the boiler and generate more steam. 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. These vehicles were virtually silent, because the steam was not released into the atmosphere.
A soda locomotive could run for several hours, but eventually the soda would become diluted and wouldn't produce enough heat to continue generating steam. 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. A stationary boiler would be hooked up and feed superheated steam through the soda to boil off the water and effectively recharge the soda.{{cite web| first=Michael| last=Hicks| url=https://www.flickr.com/photos/mulad/7222500234/in/photostream/| title=Soda motor exterior| date=May 18, 2012| website=Flickr}}
These locomotives were always called "soda locomotives" (sodium carbonate) although "caustic soda locomotives" (sodium hydroxide) would be a more precise description. The misleading terminology was most likely used, to increase their acceptance by the public, which was used to using washing soda but might have been frightened by the nasty alkali burns sitting next to several tons of hot caustic soda.{{cite web| url=http://www.douglas-self.com/MUSEUM/LOCOLOCO/soda/soda.htm| title=The Caustic Soda Locomotives| date=July 17, 2005| website=The Self Site}}
Other salts such as calcium chloride could also be used.
Advantages and disadvantages
= Advantages =
= Disadvantages =
Locomotives
- The Perkins calcium chloride engine, 1864{{cite journal| journal=The Engineer| date=20 February 1874| title=Utilisation of Waste Steam| url=https://books.google.com/books?id=EFFHAQAAMAAJ&pg=PA130}} (p. 130, middle of the right column)
- The Spence caustic soda boiler, 1874{{cite journal| journal=Engineering| date=April 1885}}{{full|date= January 2016}}{{cite journal| journal=The Engineer| date=20 February 1874| title=Steam Regeneration| url=https://books.google.com/books?id=EFFHAQAAMAAJ&pg=PA300}} (p. 300, middle column)
- The Honigmann caustic soda locomotive, 1885{{cite journal| journal=British Journal for Engineering| date=27 February 1885}}{{full|date=January 2016}}Lawrence Saunders, Notes on the Newcastle Exhibition, [https://books.google.com/books?id=hAE-AQAAMAAJ&pg=PA182 The Railway Engineer], Vol. VIII, No. 6 (June 1887); pages 180-183 (see 182, bottom of left column).
- The Baldwin soda motors, 1886