Step 1: Hang a 50-ml glass beaker containing a magnetic stirring bar in a Styrofoam box (Fig. 3.2a). Step 2: Place the box on a magnetic stirrer and check that the stirring bar rotates in the beaker (Fig. 3.2b). Step 3: Remove the beaker from the box and fill the box with an appropriate amount of liquid nitrogen so that it will be submerged in liquid nitrogen when the beaker is placed back in the box (Fig. 3.2c). Step 4: Pour 15 ml of liquid isopentane into the beaker at room temperature. Hang the beaker in the box containing the liquid nitrogen and stir the isopentane . The initial extensive bubbling of the liquid nitrogen will decrease as the isopentane cools (Fig. 3.2c). Step 5: When the peripheral part of the isopentane cools almost to the temperature of the liquid nitrogen (−196 °C) and begins to solidify, immediately place the tip of the nozzle from the propane gas tank in the cooled isopentane (Fig. 3.2d) and vigorously blow the propane gas into the cooled isopentane to liquefy the propane gas. Step 6: When the level of isopentane-propane cryogen in the beaker gradually increases, reaching a volume of about 45 ml (Fig. 3.2e, f), a ratio of isopentane to propane with 1:2–1:3, immediately stop the propane gas flow. Step 7: Cover the Styrofoam box to minimize exposure of the prepared isopentane-propane cryogen to humid air.