干燥剂在食品和药品包装中经常用来延长产品的保质期。以食品包装中常用的干燥剂硅胶、蒙脱石为试验对象，采用静态称量法研究干燥剂的平衡含水率与水分活度的关系，并用等温吸湿模型对所得试验数据进行了拟合。结果表明：硅胶和蒙脱石干燥剂的等温吸湿曲线分别为Ⅰ型和Ⅱ型等温吸附曲线，拟合精度最高的等温吸湿模型分别为Langmuir和Oswin模型；在水分活度小于0.32时，硅胶干燥剂的吸湿能力低于蒙脱石干燥剂，高水分活度时则相反。

Desiccant is often used in package of foodstuffs and medicaments to prolong preserving time. Silica gel and montmorillonite commonly used in food packaging were taken as objects of study. The relationship between water activity and equilibrium moisture content were studied by gravimetric method. The test data was fitted using moisture sorption isotherm model. The results showed that the moisture isotherms of silica gel and montmorillonite desiccant were the Ⅰ type and Ⅱ type curve respectively; the Langmuir and Oswin models are the most adaptable for fitting the adsorption isotherms of biscuit silica gel and montmorillonite desiccant respectively; the capacity of moisture adsorption of silica gel is weaker than that of montmorillonite when the water activity is less than 0.32, but it turned to the opposite at high water activity.