1 Overview
DWS-51A sodium ion concentration meter is used for the measurement of sodium ion concentration in aqueous solution. It is especially suitable for the monitoring of high-purity water quality in power plants and semiconductor factories, such as distilled water and condensed water. DWS-51A sodium ion concentration meter adopts large-size 3-digit LED digital display, which can directly test the new PNa value, Na + value and temperature value of the measured solution. The instrument has both automatic and manual temperature compensation functions. When using the sensor attached to the instrument, it can perform automatic temperature compensation and measure the temperature of the solution, or manual temperature compensation. The user can choose according to the actual situation.
This instrument uses a 701 sodium ion composite electrode and TC-1 temperature measuring electrode.
2 The main technical performance of the instrument
1. Measuring range: PNa: 0.00 ～ 8.00
Na: 23.0g / 1 ～ 2.3up / 1
T: 0 ～ 60.0 ℃
2. Accuracy: Electric meter: PNa ± 0.01
Na +: 4% FS
T: ± 1 ℃
Instrument matching: PNa ± 0.03PNa ± 1 word
Na ＋: ± 5% FS
3. Normal working conditions of the instrument:
a: Ambient temperature: 5 ～ 35 ℃
b: Relative temperature: less than 80 ℃
c: Temperature of the tested solution: 0 ～ 60%
d: Power supply voltage: AC220V ± 1.% 50HZ ± 1%
3 Working principle of the instrument
The instrument uses a sodium ion composite electrode to measure the sodium ion in the solution. The electrode potential of the sodium glass electrode immersed in the solution changes with the change of sodium ion content in the solution, and follows the special formula of energy period.
At a temperature of 20 ° C, the electrode produces a potential change of 56.16mv every time the sodium ion activity changes by a factor of 10 (ie 1PNa), so the change in the potential difference of the measurement electrode can measure the sodium ion concentration of the solution. The PNa value or Na + value of the measured liquid can be directly displayed.
H + and K + ions interfere with the sodium glass electrode. In order to ensure the measurement accuracy, the pH value of the measured solution must be adjusted to ≥pna + 3. For example, the measured solution sodium ion activity Pna5 (23 × 10-5g / L) measured solution pH The value should be adjusted to more than 5 + 3 = 8
4 Use and maintenance of the instrument
The Pna value of the aqueous solution is measured with a PNa glass electrode, which is the same as the PH value measurement, that is, there must be a known standard solution for potential, that is, the same potential must be adjusted by positioning to offset the difference between the indicator electrode and the reference electrode Asymmetric potential. The difference from the PH measurement is that the standard PNa solution has no buffering effect. It is necessary to strictly prevent the contamination of the container. In addition, special attention should be paid to the interference caused by hydrogen ions. Pay attention to these characteristics when measuring.
(1) Install the 3 electrodes and the measuring sensor (the temperature measuring electrode is not necessary for manual temperature adjustment) into the corresponding positions of the electrode holder. Before use, the sodium electrode should be soaked in 0.01mol-1 sodium chloride solution for several hours. Prepare three standard solutions of PNa3.PNa4.PNa5 respectively according to the solution preparation method in Appendix 1 of this manual. 1000ml each, and then inject the prepared polyethylene In plastic bottles (can not use ordinary plastic bottles or glass bottles), simultaneously inject two drops of 0.2 mol-1 diisopropylamine. Ammonia or add saturated barium hydroxide solution into each cup. If the solution being tested is acidic, the amount added should be increased so that the pH of the solution is greater than 10.
(2) Before the measurement, the electrode should be washed repeatedly with three drops of 0.2 mol-1 diisopropylamine in sodium-free water for more than three or four times. Turn on the power switch, generally preheat for a few minutes, the (slope) potentiometer knob is turned clockwise to the end, (temperature) potentiometer is turned to the actual temperature value of the measured solution, if you use automatic temperature compensation, insert the temperature compensation electrode, at this time ( (Temperature) The potentiometer does not work. If you want to know the temperature value, set the (select) switch to the "T" position.
(3) (Select) The switch is placed in the "PNa" position, first use the PNa4 solution, remove the installed glass electrode clip, so that the bulb and calomel ceramic core are immersed in the solution, and adjust (positioning) after 2-3 minutes ) Potentiometer to make the instrument display a value of 4.00PNa.
(4) The accuracy must be further improved. The two-point calibration method can be used, that is, the PNa5 solution is used to measure according to the above method, and the (slope) potentiometer is adjusted to make the instrument display 5.00PNa.
(5) At this time, the instrument has been adjusted, and the PNa value of the unknown solution can be measured to reach the technical index that the instrument should reach.
(6) If you want to measure the Na + value of the solution, you should set the (select) switch to the corresponding Na + level. The Na + measurement is divided into 7 levels. Each level corresponds to a PNa measurement range, and the second level Na + value is 2.30g / L—0.23g / L. Corresponding to the measurement range of 1-2PNa, and other analogy in turn.
The following problems should be noted during the specific use of this instrument:
a. Newly purchased PNa electrode or electrode that has not been used for a long time need to be cleaned with cotton cloth dipped in carbon tetrachloride or alcohol, then rinsed with water and immersed in 5% KCL for 15-20 minutes, then washed with pure water Immerse it in alkalized 0.01 mol-1 NaCL solution for several hours to make the electrode have good performance.
b. The service life of the PNa electrode is generally one year to one and a half years. If the (positioning) calibration time exceeds 10 minutes, the number is still drifting slowly and the response is unresponsive, indicating that the electrode has aged and the new electrode should be slipped.
c. When measuring a solution with a higher concentration, the sodium electrode cannot be used to measure trace solutions immediately. The electrode must be rinsed repeatedly before being immersed in pure water to recover.
d. When the temperature of the measured solution is lower than 20 degrees, the reaction speed of the PNa electrode is slower, the lower the temperature, the slower the reaction, so the reading time is also appropriately extended as the temperature drops, otherwise the higher the water temperature, the reaction time The shorter.
(7) When the instrument is not in use, the short-circuit plug should be inserted into the sodium electrode plug of the instrument to keep the plug clean.
Completeness of the instrument
1.DWS-51A sodium ion concentration meter
2.701 composite sodium ion electrode one
3.TC-1 temperature measuring electrode
4. One set of electrode holder
5. Power cord
6. Instructions
8. Certificate of conformity
9. Warranty card
appendix:
Preparation of Na + solution
Weigh 0.117 grams of sodium chloride reagent dried at a high temperature of about 100 degrees for 1 to 2 hours, and dissolve it in 2 kg of sodium-free water to form 0.001Mna + standard solution, ie PNa4, which is equivalent to 2.3ppMNa solution. PNa5 standard solution can use PNa4 Draw 50mL of the standard solution with a 50mL pipette, put it in a 500mL volumetric cup, and then use sodium-free water less than 2ppbNa + to add to the 500mL standard solution that is PNa5 immediately.
The prepared standard solution should be added with diisopropylamine. Ammonia or barium hydroxide before use.
Note: All container test cups must be washed with sodium hydroxide water 4-5 times and numbered. Solution containers with different concentrations cannot be mixed to prevent pollution.
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