178 POTASSIUM BICARBONATE 



reaction. It is soluble in its own weight of water at 60 

 Fahr., deliquesces rapidly in the air ; but as it gradually 

 absorbs carbonic acid, it again slowly dries up. Exposed 

 to a red heat, it loses water of crystallisation to the amount 

 of sixteen per cent. 



Potassium bicarbonate, or acid carbonate of potash, is 

 prepared by passing carbonic anhydride into a strong 

 aqueous solution of the neutral carbonate. It occurs in 

 transparent, colourless, right rhombic prisms ; has a mild, 

 saline, and slightly alkaline taste ; dissolves in about four 

 times its weight of water at 60 Fahr. ; when heated to 

 redness, it gives off carbonic acid and water, and is con- 

 verted into the neutral carbonate. It is distinguished from 

 the neutral carbonate by its milder, non-acrid taste, its less 

 solubility in water, its more abundant effervescence with 

 hydrochloric acid, its not deliquescing when exposed to 

 the air, and by giving, in diluted solution, no precipitate 

 with Epsom salt or corrosive sublimate. 



ACTIONS AND USES. The two carbonates have the soluble 

 alkali group actions and differ only in degree. Both resemble 

 the hydrate, but have their activity tempered and diminished 

 by combination with carbonic acid, which partly neutralises 

 the caustic OH group set free by dissociation. The neutral 

 carbonate, in concentrated solution, has much of the cor- 

 rosiveness of the hydrate. Two drachms given to a dog 

 caused vomiting, great agony, and death in twenty-five 

 minutes (Orfila). Three ounces are said to be fatal to horses 

 or cattle (Kaufmann). Its antidotes are the same as those 

 of caustic potash. The bicarbonate has virtually no irritant 

 or corrosive action, and so is often preferable as an antacid, 

 and, in virtue of its liberating carbonic acid, exerts soothing 

 effects on the irritable gastric membrane. It is less of an 

 alkali and more of a pure saline. Both carbonates are 

 antacid antidotes for overdoses of acids, and are alterative 

 and diuretic. 



MEDICINAL USES Potassium bicarbonate is occasionally 

 substituted for sodium bicarbonate to aid the emulsifying 

 of fats, and, on account of the evolution of carbonic acid, to 

 soothe the irritable stomach. Given before meals, it was 

 thought to increase gastric secretion. The experiments of 



