论文部分内容阅读
在“电导法测定弱电解质的电离常数(或难溶盐的溶度积常数)”实验中,通常是采用惠斯登交流电桥在恒温下测定溶液在电导池内的阻抗来完成的。惠斯登交流电桥由音频讯号发生器、电阻箱(三台)、示零仪器(常用高阻耳机)、可变电容、电导池构成。本实验按教材的一般要求有如下缺点:(1)所用仪器多而杂,占面积太宽,不利于操作。(2)各种仪器相对位置不固定,引起的杂散电容的影响,使指示不稳定,大大影响测量精度。(3)用高阻耳机作示零仪器,由于听力的限制,灵敏度较低,若用示波器示零,还需加装放大器。(4)用以上方法实验,开支费用较多,每套装置需一千多元。为了便于操作,并使学生在实验中充分掌握惠斯登交流电桥的结构及测量方法,同时又最大程度地降低设备费用,我们自制了如下的实验装置:
In the “conductivity method for the determination of the ionization constant of weak electrolytes (or the solubility product constant of sparingly soluble salts)” experiment, it is usually done by measuring the impedance of the solution in the conductivity cell at a constant temperature using a Wheatstone AC bridge. Wheatstone AC bridge from the audio signal generator, resistance box (three), show zero equipment (commonly used high-impedance headphones), variable capacitance, conductivity of the pool. The experiment according to the general requirements of the textbooks have the following disadvantages: (1) the use of multiple and miscellaneous equipment, accounting for the area is too wide, is not conducive to operation. (2) The relative position of various instruments is not fixed, the impact caused by stray capacitance, so that the instructions are not stable, greatly affecting the measurement accuracy. (3) high impedance headphones for zero instrument, due to hearing limitations, lower sensitivity, if the oscilloscope shows zero, but also need to install an amplifier. (4) Experiments with the above method, more expenses, each device needs more than 1,000 yuan. In order to facilitate the operation and enable students to fully understand the structure and measurement methods of the Wheatstone AC bridge in the experiment while minimizing the equipment cost, we made the following experimental setups: