ZD-2A automatic potentiometric titrator instructions

ZD-2A automatic potentiometric titrator is easy to operate, beautiful in appearance, compact and light, and the accuracy of use has been significantly improved. The indication of the instrument has been changed from the original indicator to 0.8 inch digital display. The instrument is widely used in chemical laboratories. An ideal capacity analysis instrument for various components of environmental analysis, chemical, school, metallurgy, pharmaceutical and other industries.

This instrument has the following main features:

(1) Because the instrument is more compact, the instrument can be used as a precision PH meter in the laboratory. Its accuracy is exactly the same as PHS-3C. Its function, usage and technical indicators are consistent with PHS-3C.

(2) In the titration capacity analysis, the end point potential is preset. After the titration is started, the input potential value is positive or negative, regardless of whether the potential becomes larger or smaller after the titration, and the positive or negative is changed. Precision automatic polarity reversal circuit, and automatically track the end point potential, the operator does not have to dial any control switch, which is convenient to use, and improve the control accuracy.

(3) When making pH measurement, the panel adopts potentiometer and band switch control and switching. When performing titration analysis, it adopts high-reliability touch key control, so users can choose automatic titration and manual titration.

Second, the main technical indicators

(1) Measurement range: PH: 0~14.00PH

Mv: 0～±1999mv

(2) Measurement accuracy: PH: ±0.01

Mv: 0.1% F·S

(3) Potential control accuracy: ±0.03PH or ±3mv

(4) Input impedance: not less than 1 × 1212Ω

(5) Capacity analysis repeatability: no more than 0.3% F·S

(6) Dimensions: 280×200×130

(7) Weight: 3.5Kg

Third, the method of use

When the instrument is used, it is divided into two parts according to PH usage and titration analysis. The specific use and operation methods are as follows:

(1) When using PH:

A. Turn on the power and warm up the instrument for 10 minutes.

B. Before measuring the measured solution, the instrument should be calibrated first. When it is used continuously, it can be calibrated once a day. The calibration is divided into one calibration method and two-point calibration method. For the conventional measurement, a one-point calibration method is adopted. Point calibration method.

C point calibration method:

Plug the instrument electrode into the Q9 short-circuit plug, connect the composite electrode, rinse the electrode with distilled water, and then immerse it in the buffer solution. (If the measured solution is acidic, the buffer solution should use PH=4, otherwise use PH=9. Buffer solution.) Turn the “slope” potentiometer clockwise to the end and adjust the temperature potentiometer to the temperature of the measured solution.

Adjust the “Positioning” potentiometer so that the PH value displayed by the digital display is the standard value of the buffer solution at this temperature (see Appendix 2). At this time, the calibration of the instrument is finished, and the individual knobs can no longer be moved, and the unknown solution can be measured. It is.

D, two-point calibration method:

The instrument removes the Q9 short-circuit plug, accesses the composite electrode, and the slope potentiometer rotates clockwise. The temperature potentiometer is adjusted to the actual temperature value of the measured solution, and the electrode is first immersed in the buffer solution of pH=7.

Adjust the “positioning” potentiometer so that the instrument's digital display PH value is the standard value of the buffer solution at this temperature (see Appendix 2). If the measured solution is acidic, remove the electrode from the buffer solution with pH=7. Rinse with distilled water and insert into a buffer solution of pH=4. If the solution to be tested is alkaline, insert it into a buffer solution of pH=9, and then adjust the “slope” potentiometer so that the number at this time is displayed at this temperature. The standard value.

The above two-point calibration is repeated until the two buffer solutions reach the standard value without adjusting the "positioning" and "slope". Remove the electrode from the buffer and rinse it with distilled water to measure the unknown solution.

E, measuring electrode potential

Pull out the Q9 shorting plug and connect various suitable ion selection electrodes and reference electrodes. The instrument "select" switch is set to "mv" file (the "positioning", "slope" and temperature are not effective at this time). The electrode is immersed in the solution to be tested. At this time, the digital sentence displayed by the instrument is the electrode potential of the ion selective electrode. (mv value), and the positive and negative polarity are automatically displayed.

(2) When performing titration analysis

The instrument can be used for various types of potentiometric titration. The user can insert the electrode jack of the rear panel according to different electrodes. If some electrodes cannot be directly inserted into the Q9 jack, the Q9 plug provided by the instrument can be used; The crocodile can hold the electrode tip.

A. As shown in Figure 1, install the titration device and force the silicone tube at both ends of the solenoid valve into the joint of the burette and the drip tube.

B. Insert the solenoid valve into the socket at the back of the instrument and add a standard solution to the burette.

C. Press the “Fast Drop” button to adjust the solenoid valve screw to make the standard solution flow down and drive away all the air bubbles in the liquid path.

D. Press the “slow drop” button to adjust the solenoid valve screw so that the slow drop speed is about 0.02ml per drop.

E. Refill the standard solution and press the short drop button to adjust the standard solution in the burette to zero scale.

F. Select the switch to set the “preset” file, adjust the preset potentiometer to the end point potential value of the solution dripped by the user. The mv value and the PH value are common. If the end point potential is -800mv, adjust the end point potentiometer to make the number appear as -800, if the end potential is 8.5PH, adjust the end potentiometer to make the number 850.

G. After the end point potential is preset, the selector switch sets the mv or PH position according to the requirements of use. At this time, the “preset” potentiometer cannot be moved any more.

H. When the user performs titration analysis, in order to ensure the titration precision, the titration cannot be advanced to the end point, and the titration time cannot be too long. The instrument is equipped with a long drop control potentiometer, that is, away from the end point potential. When the burette solution is directly passed through the drip, the short drop of the titration solution (about 0.02 ml each time) approaches the end point near the end point, and stops at the end point (±3mv or ±0.03PH), with a delay of about 20 seconds, the potential is not The return indicator light is on and the buzzer sounds.

Since the titration slope curves of different types of potentiometric titrations reach the end point, the titration jump values ​​are very different, so the control positions of long droplets and short droplets are also very different, such as long droplets are too long, and it is easy to drip. End point, affecting the accuracy, if the drop time is too short, the titration of a sample time will drag too long, affecting the work efficiency, so the user can first titrate a certain sample when the first drop of the potentiometer, counterclockwise (At this time, the end point potential is about 300mv or 3.00PH only long), then gradually adjust the titration control potentiometer in the titration process, so that the titration straight-through time is gradually increased until the short drop can reach the end point reliably, and the titration is saved. time.

If the user does not know the end point potential value of the solution to be tested, the end point potential can be determined by manual titration according to the two buttons of “fast drop” and “slow drop” of the instrument, that is, press away from the end point, “fast drop” button When near the end point (when the potential starts to change significantly) press the "slow drop" button (press and hold about 0.02ml per drop, every 2 seconds or so) and note the change in potential after each drop to find out each drop. The potential value with the largest amount of change is the end point potential value of the solution.

The instrument has a large range of long drop control potentiometers. When the potentiometer rotates clockwise to the end, the instrument titration can make the titration liquid pass through the end point potential about 20mv or 0.2PH, and then there will be short drops. On the contrary, counterclockwise rotation At the same time, the titrant starts to appear shortly after reaching the end point potential of about 300 mv or 3 PH and continues to drop to the end point.

Place the beaker of the drop sample on the stirrer, add the stir bar to open the left switch of the instrument, adjust the stirring speed, remove the electrode, and immerse the electrode in the dripped solution.

Press the “Titration Start” button, the instrument will start titration, first pass (long drop) and then short (according to the position of the long drop control potentiometer) reach the end point delay for about 20 seconds, the end indicator light is on, and the buzzer sounds, then the instrument At the end lock state, press the “Reset Zero” button again, the instrument pushes out the locked state, and the electrode and the drip tube are removed from the liquid surface and rinsed with distilled water.

Fourth, repair and maintenance

In order to prevent the silicone tube from aging due to long-term use, the instrument should be completely relaxed. Therefore, the user should press the fast drop button repeatedly while adjusting the solenoid screw. You should be able to hear the quick drop button repeatedly. When the solenoid valve emits a "drop" sound, the flow of the solution after the titration tube is filled with the titration solution also flows out or is interrupted with the action of the button. If the solution leaks, it is possible to adjust the screw too loose, the silicone tube is broken or the silicone slides out of the control knife. outer.

Solenoid valve silica gel is too long to be used for aging (production adhesion, cracking) must be replaced in time. When replacing, first unscrew the upper cover of the solenoid valve, remove the old tube, pass the new tube through the center of the solenoid valve, and turn on the solenoid valve power supply. Press the “Quick Drop” button on the right hand, and push the electromagnetic valve on the left hand to let it suck in, increase the middle gap, and then screw the upper cover of the solenoid valve with your left hand. Otherwise, it is easy to slide the silicone tube out of the control knife when the cover is attached.

If the liquid path is found to be unreachable, check if the solenoid valve screw is too tight and the burette and the drip tube are blocked.

If it is found that the liquid path leaks, check whether the solenoid valve screw is too loose, so that the electromagnetic valve does not absorb the moving iron, or the silicone tube is aged and cracked.

If the instrument is not used for a long period of time, the silica gel in the solenoid valve should be taken out and rinsed with distilled water.

The composite glass electrode is used for a long time. If the instrument is found to be unresponsive, the measurement data drifts for a long time and cannot work stably. Under normal circumstances, the electrode may be aging and must be replaced in time.

Fifth, the complete set of instruments

ZD-2A automatic potentiometric titrator

E201 composite electrode

212 type reference electrode

213 type platinum electrode

216 type silver electrode

231 PH glass electrode

Titration device

Drip tube 3

Silicone tube

Instruction manual

Certificate of conformity

Power cord

Sixth, the schedule

The buffer solution should be properly prepared as shown in Appendix 1.

Appendix 1. Preparation of Buffer Solution:

(1) The PH4 solution was dissolved in 1000 ml of double distilled water using 10.21 g of GR potassium hydrogen phthalate.

(2) The pH 6.86 solution was dissolved in 1000 ml of double distilled water with GR 3.4 g of potassium dihydrogen phosphate and 3.55 g of GR dibasic phosphate.

(3) The pH 9.20 solution was diluted with 3.81 g of GR borax in 1000 ml of double distilled water.

Or use the instructions for the packet reagent.

Appendix 2. Comparison table of PH value and temperature of buffer solution:

Jiangyan Yinhe Instrument Factory

Address: Building 6, Zhengda Garden, Jiangyan City

Telephone, 88081006

Zip code: 225500

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