The present study developed a microdevice system equipped with a microdevice for solid powder dissolution, with the purpose of implementing a means for dissolving against exposure and solving the problems in dispensing such as scattering of drugs and foaming in solution. The system performance was evaluated by a dissolution process of anhydride sodium acetate. We studied a method of slowly introducing solid powder into liquid using a T-tube. Anhydride sodium acetate that was filled into the tip of a tube with an inner diameter (ID) of 1.5 or 2.0 mm was introduced into pure water in a T-tube by compressed air. The introduction amount of anhydride sodium acetate showed two peaks against linear velocities of air, and the peak at a higher linear velocity was larger with slug flow in which air and liquid alternatively flowed. Foaming in liquid was not observed at either linear velocity of air. The tube with an ID of 2.0 mm and a higher linear velocity of air were adopted since the introduction amount per flow rate of air with a larger ID of 2.0 mm was larger than that of 1.5 mm. We fabricated a microdevice system, where the residence time was changed by circulating liquid based on the concentration of liquid measured with an inline absorption spectrometer. The flow rate of liquid was at first set to 1.5 mL/min (1.5 x 10(-6) m(3)/min), and then alternatively switched between 3.0 and 1.5 mL/min (3.0 x 10(-6) and 1.5 x 10(-6) m(3)/min) every 3 min. The dissolution process was performed within around 12 min, which was shorter than about 30 min in the conventional manual mixing. The closed microdevice system for solid powder dissolution provided the objective sodium acetate aqueous solution of 29.3 mg/mL (29.3 kg/m(3)) concentration with an error of 9.9%.