In continuation of previous works, X-ray diffraction pattern, specific gravity, and gram volume of pentobarbital calcium and calcium pyruvate isoniasone were examined. Pentobarbital calcium tablet is similar to calcium p-aminosalicylate in that its tablet disintegration requires longer time with passage of time, while the tablets of calcium pyruvate isoniasone produce cracks and self-destruction in the air. Changes in the state of crystal water were also examined and relationship of these physical data with retarded disintegration and self-destruction of these tablets was also examined.
Pentobarbital dihydrate, similar to calcium p-aminosalicylate, becomes amorphous when dehydrated and transition state of hydrate-anhydrate appears over a long period of time. Gram volume of the dihydrate is greater than that of anhydrate. If the tablet is formed from granules partially in amorphous state by drying and other condition, and allowed to absorb moisture, the tablet will not disintegrate for more than 30minutes whereas tablets immediately after tabletting underwent disintegration in a few minutes.
Calcium pyruvate isoniasone differs from calcium p-aminosalicylate and forms a hydrate with different crystal lattice, between the stable heptahydrate and trihydrate. Self-disintegration of this tablet is considered to be due to changes in crystal structure between the heptahydrate and trihydrate. Vapor pressure of heptahydrate crystal is high and the gram volume of stable heptahydrate is small, contrary to the case of calcium p-aminosalicylate and pentobarbital calcium, with extremely short period of transition state. Tabletting of granules mixed with the trihydrate will result in sudden appearance of distortion in a tablet by absorption of moisture, accompanying lattice formation. Therefore, such a tablet undergoes complete self-destruction within 20-30minutes in a room with relative humidity of 76% and loses the original form.