2 1 8 CHEMISTRY. 



predated by learning that 200,000 tons of "soda ash" (crude 

 sodium carbonate), worth ten million dollars, are made an- 

 nually in Great Britain alone. Carbonate of soda, when 

 crystallized, has a remarkably large amount of water com- 

 bined with it 63 parts in every 100. When it is wholly 

 anhydrous that is, when it has lost all its water of crystal- 

 lization it is of more than twice the strength of the crys- 

 talline salt. If the crystals be heated, they fuse in their own 

 water of crystallization. Many mineral waters contain con- 

 siderable of this salt. 



302. Sodium Bicarbonate. This salt is, strictly speak- 

 ing, hydro-sodium carbonate, NaHCO 3 . It is much used in 

 making soda-powders. The powder in the blue paper is 

 the bicarbonate of sodium, while that in the white paper is 

 tartaric acid. When these are dissolved in water in separate 

 tumblers, and the two solutions are poured together, the 

 tartaric acid at once seizes the soda, forming tartratc of 

 sodium, and the carbonic anhydride, set free, effervesces 

 strongly. The same effect is produced if you mingle the 

 two powders intimately, and then throw the mixture into 

 the water. 



303. Sodium Sulphate, or Glauber's-Salt, Na 2 SO 4 -f 10lI 2 O. 

 This salt received the name of Glauber's-salt because it 

 was first obtained by means of a chemical process by a Ger- 

 man chemist of that name. It occurs in nature, but not 

 abundantly, except in a few localities, one of which is a cave 

 in the island of Hawaii, from which the natives gather it 

 for medical use. Ordinarily it is obtained by the action of 

 sulphuric acid upon common salt. More than half of this 

 salt in its crystalline state is water, and exposed to the air 

 the crystals effloresce, and fall to powder. 



There is another sodium sulphate containing less sodium, 

 NaHSO 4 ; this is formed when the sulphuric acid is used in 

 excess. It has a very acid reaction. 



