US EPA

2067523 

Journal Article 

Neutralization process of synthetic hydrotalcite with hydrochloric acid 

Takagishi, Y; Iwamoto, K; Maekawa, H 

1978 

No 

Yakuzaigaku
ISSN: 0372-7629 

IPA/79/362039 

Pract 

Yakuzaigaku 

166-173 

jpn 

IPA COPYRIGHT: ASHP The neutralization process of synthetic hydrotalcite (Mg6Al2(OH)16CO34H2O;I) in hydrochloric acid solution is examined in detail and the mechanism of action of synthetic hydrotalcite yielding excellent antacid characteristics such as rapid pH elevation and duration of the optimum pH range of 4.0 to 4.5 is described. The rapid pH elevation is ascribed to 2 different reactions at the initial stage of neutralization. The one is the simple neutralization of hydrochloric acid with I crystals and the other is the neutralization with carbonate ion produced by the exchange reaction between the carbonate group in the crystals and chloride ion in hydrochloric acid solution. The duration of the optimum pH range may be attributed to the following mechanism. When a pH value is elevated to about 4, dissolution of the crystal stops because of the low solubility of aluminum hydroxide in the crystal, while the slow dissolution of magnesium hydroxide in the crystal proceeds, releasing hydroxyl ion. The hydroxyl ion, however, is consumed by the hydrolysis of aluminum ion produced by dissolution of the crystal at the initial stage of neutralization.