SODIUM. 



ratures which are higher, although short of a red heat, the salt 

 being anhydrous, appears to have lost its solubility in water ; 

 at least it is not affected at first when thrown in powder into 

 boiling water, but gradually dissolves by continued digestion, 

 and passes into the preceding variety. (Phil Trans. 1833, p. 

 275.) 



Borax, Biborate of soda; Na O, <2BO 3 -HOHO; 1263.3. + 

 1125 or 101.23+90. This salt is met with in commerce in 

 large hard crystals. It is found in the water of certain lakes in 

 Transylvania, Tartary, China, and Thibet, and is deposited in 

 their beds by spontaneous evaporation. It is imported from 

 India in a crude state, and enveloped in a fatty matter, under 

 the name of Tinkal, and afterwards purified. But nearly the 

 whole borax consumed in England is at present formed by 

 neutralising with carbonate of soda, the acid from the boracic 

 lagoons of Tuscany. The ordinary crystals of borax are prisms 

 of the oblique system, containing 10 atoms of water, which are 

 not efflorescent when free from carbonate (Mr. O. Sims) ; but 

 it also crystallizes at 133 in regular octohedrons, which contain 

 only 5 atoms of water. This salt has a sweetish, alkaline taste; 

 for although containing an excess of acid, it has an alkaline re- 

 action, like the bicarbonate of soda. 



The anhydrous salt is very fusible by heat, and forms a glass. 

 This glass possesses the property of dissolving most metallic 

 oxides, the smallest portions of which colour it. As the metal 

 may often be discovered by the colour, borax is valuable as a 

 flux in blow-pipe experiments. As pieces of metal could not be 

 soldered together, if covered by oxide, borax is fused with the 

 solder upon the surface of the metals to be joined, to remove 

 the oxide. Borax is also a constituent of the soft glass, known 

 as jewellers' paste, which is coloured to imitate precious stones. 

 But the most considerable consumption of this salt is at the 

 potteries, in the formation of a glaze for porcelain. 



A neutral borate of soda was formed by Berzelius by calcining 

 strongly 1 eq. of borax with 1 eq. of carbonate of soda, when 

 carbonic acid is expelled. The solution yields a salt belonging 

 to the oblique prismatic system, of which the formula is, NaO, 

 BO 3 H-8HO. When heated, it fuses in its water of crystalliza- 

 tion, and is expanded into a vesicular mass of extraordinary 

 magnitude, by the vaporisation of that water. 



When borax is fused with carbonate of soda in excess, the 



