Antacids, certain drugs used to neutralize acid, either in the alimentary canal or circulating in the blood. For the former indication, the carbonates and bicarbonates of soda and potassa, lime water, chalk, and magnesia with its carbonate, are used. The symptom which they temporarily relieve is, however, often more efficiently treated by regulated diet or by mineral acids. For the second purpose we have, besides the alkalies and their carbonates, including littisa, which is weight for weight the most powerful, the salts formed by them with acetic, tartaric, and citric acids. These acids, when in combination with alkalies, take up in the blood more oxygen, forming carbonic acid, which forms with the bases bicarbonates; so that the alkalization of the blood is attained without the local gastric troubles which might attend the administration of the caustic or carbonated alkalies in equivalent doses. The acetate of potassa, or corresponding salts, are largely used in the treatment of acute rheumatism where they render the urine alkaline.

They also considerably increase its quantity.