1. A model was proposed to explain the effect of amorphous silic acid on the mode of degradation for thiamine HCI and L-ascorbic acid in multivitamin capsule. 2. Neither signicant difference on vitamins stability between the different diluents nor significant effect of amorphous silic acid on vitamin stability can be observed in this investigation. 3. Arrhenius equation can be applied to predict the expiry date for the multivitamin capsule which contains 1.5% amorphous Silic acid as inert excipient. 藥品在固體劑型中之分解機序，一直無確定之理定之理論。非晶質矽酸，本係Chromatographic separation使用之吸著劑，因其優秀之吸著性、分散性，及可保持藥劑乾燥易流動，故廣泛被使用做固體劑型之不活性添充料。本研究就非晶質矽酸添加在多種維生素膠囊劑時，其對水溶性維生維之分解型態之影響，作理論模型之解析。所獲知見為:1.水溶性維生素在結晶性乳糖，及在結晶性纖維素中並無有意義之安定度變化。2.非晶質矽酸之添加，並不影響水溶性維生素之安定度，但能改變其分解型態。3.添加1.5%之無晶質矽酸時，水溶性維生素在固體劑型中之分解型態不論在水溶性之賦形劑或在非水溶性之賦形劑中，依擬一次反應型式進行。
