Gold capillary  Properties: When there is a current flowing through the measuring battery, there is an ohmic potential drop in the solution between the two electrodes, which is more significant for solutions with higher resistivity and larger currents. In order to minimize its impact on the potential measurement, pull the glass tube at the solution end of the reference electrode into a capillary, that is, the Lukin capillary, and make it as close as possible to the working electrode, so that there is almost no current through the measurement loop of the reference electrode, so that it can be used. The high-impedance voltmeter measures more accurate potential data. Function: The function of the Lujin capillary is to eliminate the resistance overpotential; three electrodes (electrode to be measured, auxiliary electrode, reference electrode), auxiliary electrode and electrode to be measured, change the resistance in the circuit, control the current density of the electrode to be measured, and get Different overpotentials; the reference electrode and the electrode to be measured are used to measure the potential of the electrode to be measured by the cancellation method. Use: The tip of the Lukin capillary should be as close to the surface of the research electrode as possible to reduce the ohmic potential drop as much as possible. However, it should not be too close, otherwise it will have a significant shielding effect on the electrode surface and affect the current distribution. In order to reduce the ohmic voltage drop of the solution without producing obvious shielding effect, the distance between the tip and the surface of the research electrode should not be less than the outer diameter of the Lukin capillary.

2 Preparation, use and maintenance 

[1]

1. Add 3 grams of agar and 97ml of distilled water to the beaker, and heat it on a water bath until it is completely dissolved. Then add 30 grams of KCl and stir thoroughly. After the KCl is completely dissolved, use a dropper or siphon to add this solution to a glass tube that has been bent beforehand, and let it stand until the agar is condensed before use.

2. Agar-saturated KCl salt bridge cannot be used for solutions containing Ag+, Hg2+ and other ions that interact with Cl- or ClO4- and other substances that interact with K+.

3. The test temperature above 80℃ will cause damage to the salt bridge. It is best to control the test temperature below 70℃.

4. After the experiment, the salt bridge needs to be rinsed with deionized water to avoid contamination of the electrode, and then soaked in a saturated KCl solution. Pay attention to frequently add deionized water to prevent the salt bridge from cracking and damage.

5. After the experiment, the saturated calomel electrode should be immersed in saturated KCl solution to prevent deterioration of the composite electrode supplement solution. In future use, you should first check whether the replenishment solution inside the electrode is saturated (generally, there will be oversaturated KCl crystals in it).

6. Note: It is strictly forbidden to store other items in the beaker for storing saturated calomel electrode and salt bridge, and the dropper placed in it shall not be used for other purposes