Effervescent tablets carbon dioxide, sources

Ascorbic acid can be used as the acid source. The speed of release of carbon dioxide from a mixture of ascorbic acid and NaHCOs is comparable with that produced by citric or tartaric acid-NaHCOs combinations. Since ascorbic acid is less hygroscopic than citric and tartaric acid, using ascorbic acid as the only acid source makes it possible to produce effervescent tablets in a non-airconditional area. ... 

Sodium glycine carbonate Source of carbon dioxide for effervescent tablets... 

As an excipient, potassium bicarbonate is generally used in formulations as a source of carbon dioxide in effervescent preparations, at concentrations of 25-50% w/w. It is of particular use in formulations where sodium bicarbonate is unsuitable, for example, when the presence of sodium ions in a formulation needs to be limited or is undesirable. Potassium bicarbonate is often formulated with citric acid or tartaric acid in effervescent tablets or granules on contact with water, carbon dioxide is released through chemical reaction, and the product disintegrates. On occasion, the presence of potassium bicarbonate alone may be sufficient in tablet formulations, as reaction with gastric acid can be sufficient to cause effervescence and product disintegration. 

Sodium bicarbonate is generally used in pharmaceutical formulations as a source of carbon dioxide in effervescent tablets and granules. It is also widely used to produce or maintain an alkaline pH in a preparation. 

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