100 SALINES. [IV, 



the decomposition of salt, starting from the simple equation 

 NaCl + HO=NaO + IICl, that is, that water and salt, at a 

 high heat, would mutually form caustic soda and chlorohydric 

 acid. This decomposition does take place, but he found that 

 by the assistance of alumina it was more perfect, the soda 

 being retained by the alumina and the acid passing off. The 

 soda is extracted by water from the alumina and the latter 

 used again. 



Tilghman also prepares Glauber's salt by heating to redness 

 a mixture of common salt and gypsum, and passing steam 

 through • it, and then extracting by water. The Glauber's 

 salt, mixed with alumina, is heated to redness, while steam is 

 passed over it, and the soda then extracted from the alumina 

 by water. (Rep. Pat. Inv. 1847.) 



Testing Bicarbonate of Soda. — Chevalier (Liebig's Annalen, 

 1847) detects the presence of neutral carbonate in bicarbonate 

 alkali, by adding starch-sugar to the aqueous solution of the 

 latter, and heating. The mixture yellows or browns if any 

 neutral carbonate is present. 



The soda obtained from the soda-process is chiefly used for 

 fluxing sand to make glass, for decomposing fats to make soap, 

 or to neutralize acids. The boracic acid of the Tuscan lakes, 

 neutralized by soda, yields the borax of commerce ; and phos- 

 phoric acid, from bones, yields phosphate of soda, which is 

 employed in dyeing and calico-printing. 



B. The muriatie acid obtained as an incidental product in 

 making soda-ash, besides its use for dissolving metallic oxides, 

 is extensively employed in making bleaching salt. When 

 muriatic acid is heated with black oxide of manganese, its 

 hydrogen is oxidized to water by the oxygen of the oxide, and 

 chlorine gas is set free. When this is passed into lime, chlo- 

 ride of lime or bleaching-salt is made, and passed for a long 

 time into a solution of potash, the chlorate of potassa is 

 formed. 



Chloride of Lime. — According to Mene (Comptes Rendus, 

 1847), bleaching-salt may be made pure and expeditiously, by 

 saturating slaked lime with water highly charged with chlorine. 



