C 10 3 



table alkali, or potassa, is the common alkali, or pot- 

 assa, is the common alkali in the vegetable kingdom. 

 This substance in its pure state is white, and semi- 

 transparent, requiring a strong heat for its fusion, and 

 possessed of a highly caustic taste. In the matter 

 usually called pure potassa by chemists, it exists com- 

 bined with water ; and in that commonly called pearl 

 ashes, or pot-ashes in commerce, it is combined with 

 a small quantity of carbonic acid. Potassa in its com- 

 bined state, as has been mentioned, page 47, consists 

 of the highly inflammable metal potassium, and oxy- 

 gene, one proportion of each. 



Soda, or the mineral alkali, is found in some 

 plants that grow near the sea ; and is obtained com- 

 bined with water, or carbonic acid, in the same man- 

 ner as potassa ; and consists, as has been stated, 

 page 47, of one proportion of sodium, and two pro- 

 portions of oxygene. In its properties it is very simi- 

 lar to potassa ; but may be easily distinguished from it 

 by this character : it forms a hard soap with oil ; 

 potassa forms a soft soap. 



Pearl ashes, and barilla and kelp, or the impure 

 soda obtained from the ashes of marine plants, are 

 very valuable in commerce, principally on account of 

 their uses in the manufacture of glass and soap. Glass 

 is made from fixed alkali, flint, and certain metallic 

 substances. 



To know whether a vegetable yields alkali, it 

 should be burnt, and the ashes washed with a small 

 quantity of water. If the water, after being for some 

 time exposed to the air, reddens paper tinged with 



