CHAPTER XXI 

 ALKALIES AND ALKALINE EARTHS 



. This group is composed of the alkaline salts of potassium, 

 sodium, lithium and certain salts of the alkaline earths, calcium 

 and magnesium. The potassium, sodium and lithium ions are 

 absorbed readily from the gastro-intestinal tract and exert a sys- 

 temic action following the local action in the stomach. On the 

 other hand, the magnesium and calcium ions are not readily ab- 

 sorbed and exert their action upon the intestines. The magnesium 

 salts tend toward purgation and the calcium toward constipation. 

 The alkalies may be divided into : 



1. Caustics. These are the hydroxides of potassium, so- 

 dium, and the oxide of calcium. They are all strong irritants, 

 even in weak solution. The caustic action is due to their power of 

 abstracting water from the tissues, saponifying fats, and dissolving 

 albumen. This action has been discussed under the head of 

 escharotics, p. 344. 



2. Those of Milder Action. These are the carbonates and bi- 

 carbonates of potassium, sodium and lithium, and the hydroxides and 

 carbonates of magnesium and calcium. 



GROUP ACTION 



Antagonists and Incompatibles. Alkalies and their car- 

 bonates are incompatible with acids and metallic salts. Ammonium 

 carbonate is incompatible with acid salts and lime water. 



External and Local Action. The hydrates of sodium and 

 potassium are rubifacient and caustic according to concentration. 

 Moderate solutions irritate the skin, soften and dissolve the epider- 

 mis and horny tissues. The caustic action has been discussed under 

 the head of escharotics, which see p. 344. The carbonates have a 

 similar but weaker action. The bicarbonates, citrates, acetates and 

 bitartrates possess no local action; the ammonium preparations do 

 not correspond with the actions of the above, they penetrate the outer 

 layers of the skin and cause an effusion of serum with vesication and 

 even pustulation if the vapor is confined and in concentration. 



Digestive System. Small doses are thought to promote the 

 secretion of gastric juice. Large doses neutralize the free hydro- 

 chloric acid in the stomach and by rendering the chyme neutral or 



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