56 



CHEMISTRY. 



and pearl ashes,) is procured by lixiviating the ashes of inland plants, 

 and evaporating to dryness ; purided by redissolving in water, and 

 boiling. The pure carbonate (salt of tartar,) is made by decompo- 

 sing cream of tartar by a high heat. Composition, KO+CO^. 



The bicarbonate, KO+2CO3, is formed by passing a stream of 

 carbonic acid through a solution of the carbonate. It is not so solu- 

 ble as the carbonate. A sesquicarbonate is said to exist. 



The sulphate, KO+SOg, is the residue left in the retort in the 

 preparation of nitric acid. The bisulphate, KO + 2SO3, is more 

 soluble, and has an acid taste and reaction. There is also a sesqui- 

 sulphate. 



The nitrate, KO+NO5, named also nitre and saltpetre, occurs 

 native, as an efflorescence on certain soils ; — is manufactured also 

 from artificial nitre-beds. Shape of crystals, six-sided prisms ; very 

 soluble; contains water mechanically confined, which causes the 

 crystals to decrepitate when thrown upon hot coals. When heated, 

 it gives off oxygen, and is converted into a nitrite ; a high heat 

 entirely decomposes it. From its power of imparting oxygen, it is the 

 active ingredient in gunpowder, which is a mixture of nitre, char- 

 coal, and sulphur. When gunpowder is fired, the oxygen of the 

 nitre combines with the carbon to form carbonic oxide ; the sulphur 

 with the potassium ; and the nitrogen is set free. 



The chlorate, KO+CIO^, is remarkable for its deflagrating pro- 

 perties ; it yields a large quantity of oxygen gas, on being heated. 



Sulphur, chlorine, iodine, and bromine, also form compounds 

 with potassium. 



Tests for the salts of potassa. — 1. Tartaric acid in excess gives 

 the sparingly soluble bitartrate, (cream of tartar.) 2. A solution of 

 chloride of platinum causes a yellow precipitate. 3. The alcoholic 

 solution of carbazotic acid precipitates the yellow carbazotate of 

 potassa. 4. The salts of potash usually colour the flame of the 

 blowpipe purple or violet. 



SODIUM. 



History and mode of preparation the same as those of potassium. 



Prop. — A white metal ; resembles potassium in most respects ; 

 sp. gr. -972 ; decomposes water with great violence, but does not in- 

 flame on account of its rapid motion; if this be restrained by means 

 of gum or sugar, it takes fire and is converted into soda. Eq. = 

 23-3 ; Symb. (Natrium,) Na. It forms two compounds with oxygen, 

 the protoxide (soda,) Na O, and the peroxide, Na O3 ; these are 

 formed like, and correspond with, the analogous compounds of 

 potassium. 



Hydrate of soda, NaO + HO, — prepared from the carbonate by 

 the action of quicklime. Very similar in its properties to the hydrate 

 of potassa. 



