SODIUM. 145 



When sodium phosphate is heated to a low red heat it loses water, 

 and is converted into pyrophosphate, which, dissolved in hot water, 

 and crystallized, forms the sodium pyrophosphate, Na 4 P 2 O 7 .10H 2 O of 

 the U. S. P. 



The normal sodium phosphate, Na 3 PO 4 , is known also, but it is not a very 

 stable compound, being acted upon even by the moisture and carbon dioxide 

 of the air, with the formation of sodium carbonate and disodium hydrogen 

 phosphate, thus : 



2Na 3 PO 4 + H 2 O + CO 2 = 2Na 2 HPO 4 + Na,CO 3 . 



Sodium nitrate, Sodii nitras, NaNO 3 = 85 (Chili saltpetre, Cubic 

 nitre). Found in nature, and is purified by crystallization. The 

 crystals are transparent, deliquescent, and readily soluble. 



Sodium nitrite, NaNO 2 , is formed by heating the nitrate to a sufficiently high 

 temperature to expel one-third of the oxygen ; or, better, by treating the fused 

 nitrate with metallic lead, which latter is converted into oxide. The sodium 

 nitrite which is formed is dissolved and purified by crystallization. 



Sodium borate, Sodii boras, Na 2 B 4 O 7 -f 10H 2 O = 382.2 (Borax^ 

 This salt occ'Ury tcr "Clear Lake, Nevada, and in several lakes in Asia. 

 It is manufactured by adding sodium carbonate to the boric acid 

 found in Tuscany, Italy. It forms colorless, transparent crystals, 

 but is sold mostly in the form of a white powder. It is slightly 

 efflorescent, is soluble in 16 parts of cold, and in 0.5 part of boiling 

 water ; insoluble in alcohol, but soluble in one part of glycerin at 

 80 C. (176 F.). When heated, borax puffs up, loses water of 

 crystallization, and at red heat it melts, forming a colorless liquid 

 which, on cooling, solidifies to a transparent mass, known as fused 

 borax, or borax glass. Molten borax has the power to combine with 

 metallic oxides, forming double borates, some of which have a char- 

 acteristic color, for which reason borax is used in blow-pipe analysis. 

 Borax has antiseptic properties, preventing the decomposition of some 

 organic substances. 



Other sodium salts which are official are sodium hypophosphite, 

 NaPH 2 O 2 -{-H 2 O; bromide, NaBr; iodide, Nal; chlorate, NaClO a . 

 These salts may be obtained by processes analogous to those given 

 for the corresponding potassium compounds. 



Tests for sodium. 

 (Sodium chloride, NaCl, may be used.) 



1. As all salts of sodium are soluble in water, we cannot precipi- 

 tate this metal in the form of a compound by any of the common 



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