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A、B、C分别是长3～3cm的玻管;它们之间借助于橡胶管相对固定。D是3～4层的圆形塑料膜片。B的内端口用细砂纸磨平,涂少量凡士林,C的内端口为一斜面,通过B和C的接触点抵住D。此即构成一单向导管,它对流体具有单向导通性。笔者经反复实验,只要塑料膜的选材(厚度、硬度等)适中,其灵敏性是较高的。应用举例 1.将单向导管安装在实验室制取O_2、CH_4等装置的导管上,排水取气时可以防止反应器温度降低而产生的倒吸现象。 2.在HCl、NH_3的水吸收实验中,用单向导管可以代替倒漏斗,把导管末端直接插入水中。
A, B, and C are glass tubes with a length of 3 to 3 cm, respectively; they are relatively fixed by means of a rubber tube. D is a 3 to 4 layer round plastic film. The inner port of B is smoothed with a fine sandpaper and coated with a small amount of Vaseline. The inner port of C is an incline, and the contact point between B and C is against D. This constitutes a unidirectional catheter that is unidirectional to the fluid. After repeated experiments, as long as the material (thickness, hardness, etc.) of the plastic film is moderate, the sensitivity of the film is high. Application Example 1. The unidirectional catheter is installed on the catheter of O_2, CH_4 and other devices in the laboratory. When the water is taken out from the drain, the back-suction phenomenon caused by the decrease of the temperature of the reactor can be prevented. 2. In the water absorption experiments of HCl and NH 3 , a unidirectional catheter can be used instead of the inverted funnel to insert the end of the catheter directly into the water.