CHLORIDE OF SODIUM. 463 



properties: 1st. All its salts are soluble in water, and it is 

 therefore not precipitated by tartaric acid, chloride of platinum, 

 or any other reagent. 2nd. With sulphuric acid it affords a salt 

 which crystallizes in large efflorescent prisms, easily recognised 

 as Glauber's salt. 3rd. Its salts communicate a rich yellow 

 tint to flame. 



Sulphurets of sodium. These compounds so closely resemble 

 the sulphurets of potassium as not to require a particular des- 

 cription. The protosulphuret of sodium crystallizes from a 

 strong solution in octohedrons. This salt contains water of 

 crystallization ; in contact with air it rapidly passes into caustic 

 soda, and the hyposulphite of the same base. 



Chloride of sodium. Sea salt, Common salt ; Na Cl ; 733.6 or 

 58-78.- Sodium takes fire in chlorine gas, and combining with 

 that element, produces this salt. The chloride of sodium is 

 also formed on neutralising hydrochloric acid, by soda or its 

 carbonate, and is obtained thus in the greatest purity. Sea- 

 water contains 2.7 per cent of chloride of sodium, which is the 

 most considerable of its saline constituents (analysis of sea- 

 water at page 266). Salt is obtained from that source in 

 warm climates, as at St. Ubes, in Portugal, on the coast of the 

 Mediterranean near Marseilles, and other places where sponta- 

 neous evaporation proceeds rapidly; the sea-water being re- 

 tained in shallow basons or canals, on the surface of which a 

 saline crust forms, with the progress of evaporation, which is 

 broken and raked out. Sea-water is also evaporated artificially, 

 by means of culm, or waste coal, as fuel, on some parts of the 

 coast of Britain, but as much for the sake of the bittern as of 

 the common salt it affords. The evaporation is not carried to 

 dryness, but when the greater part of the chloride of sodium is 

 deposited in crystals, the mother liquid, which forms the bittern, 

 is drawn off; it is the source of much of the Epsom salt and 

 other magnesian preparations of commerce. Other inexhausti- 

 ble sources of common salt are the beds of sal-gem or rock 

 salt, which occur in several geological formations posterior to 

 the coal, as at Northwich in Cheshire, in Spain, Poland, and 

 many other localities. These beds appear to have been 

 formed by the evaporation of salt lakes without an outlet, in 

 which the saline matter, continually supplied by rivers, had 

 accumulated, till the water being saturated, a deposition of 

 salt took place upon the bottom of the lake. The salt is some- 



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