380 CARBONATES. 



2. NAMES. The Nitre of the scriptures is the carbonate of soda.* 

 Anciently nitrum or natron, and at Tripoli, called Trona. 



3. PREPARATION. 



(a.) Carbonate of soda of the shops, may be purified by dissolving 

 it in J or of its weight of water. -\ 



(b.) Effloresced carbonate of soda is the purest, as it thus sepa- 

 rates from other salts. 



(c.) The solution is to be evaporated at a loiv heat, and the crys- 

 tals of muriate of soda skimmed off, till they cease to be produced, 

 and then the solution may be suffered to crystallize by cooling. f 



4. PROPERTIES. 



(a.'j The crystals are decahedra, composed of two quadrilateral 

 pyramids, united at the bases, and truncated at their apices ; the pri- 

 mary is an oblique rhombic prism. 



. (6.) Taste is alkaline but not caustic; turns blue vegetable colors 

 green. 



ic.) Specific gravity 1.3591. 

 d.) Soluble in 2 parts of water at 60, and in somewhat less than 

 1 part at 212. As the solution cools it deposits crystals. The 

 strongest permanent solution, at common temperature, has the specific 

 gravity 1.26. 



(e.) The bi-carbonate ofpotassa is scarcely altered by the air; the 

 carbonate deliquesces, but the carbonate of soda, on account of its 

 large quantity of water of crystallization, (62.69 per cent.) effloresces 

 rapidly and falls into powder. 



(f.) By being again dissolved in water, it crystallizes anetv. 



(g.) Readily suffers the aqueous, and by ignition, the real igneous 

 fusion. 



(A.) By a very violent heat most of its carbonic acid is expelled, 

 but not the whole. 



5. PROPORTION OF ITS PRINCIPLES. 



(.) By the action of a known and a sufficient weight of sulphuric 

 acid, the quantity of carbonic acid is determined, and this action join- 

 ed with the effects of heat, has given the following for its composi- 

 tion. Acid 13.98, base 23.33, water 62.69 = 100.00, and omitting 

 the water, 



Acid, - - 4 1.23 or 1 proportion =22 



Soda, - - - 58.77 or 1 =32 



100.00 54 and the crystals of 



* See p. 251, (Soda.) t Four. Vol. IV, p. 51. 



t The calcined acetate, dissolved and filtered, and the bi-carbonate heated in the 

 same manner, afford a pure carbonate. 



