The 701 is a sodium ion composite electrode combining sodium-sensitive measuring element and reference in one body. Measuring range 10⁻¹ to 10⁻⁵ mol/L Na⁺, temperature range 20–40°C. Glass shaft Φ12×120mm, 1.0 mol/L NH₄Cl fill solution, BNC connector. No separate reference electrode required.
The 701 sodium ion composite electrode is a combination electrode that integrates the sodium-sensitive ion-selective measuring element and the reference electrode into a single glass body — eliminating the need for a separate reference electrode and simplifying the measurement setup compared to a two-electrode configuration such as the 6801 indicator electrode.
The 701 uses 1.0 mol/L NH₄Cl as the reference fill solution rather than the conventional KCl used in pH and conductivity electrodes. This is deliberate: ammonium chloride is selected to avoid introducing potassium ions into the measurement environment, as K⁺ can interfere with the sodium-sensitive glass membrane and affect the accuracy of sodium ion readings. This design consideration makes the 701 particularly well suited to samples where sodium is the target analyte and minimal ionic interference is important.
The glass shaft (Φ12×120mm) provides chemical resistance across standard aqueous sample types, and the BNC connector ensures compatibility with standard ion meters. Operating within a 20–40°C temperature range, the 701 is suited to controlled laboratory environments for routine sodium ion analysis.
| Model | 701 |
| Description | Sodium Ion Composite Electrode |
| Measuring Range | 10⁻¹ ~ 10⁻⁵ mol/L |
| Temperature Range | 20 – 40°C |
| Shaft Material | Glass |
| Fill Solution | 1.0 mol/L NH₄Cl |
| Dimensions | Φ12 × 120 mm |
| Connector | BNC |
The 701 is a composite electrode with both the sodium-sensitive measuring element and reference system in one body — no additional reference electrode is needed. The 6801 is an indicator electrode (half-cell) that requires a separate reference electrode to complete the measurement circuit. The 701 covers 10⁻¹ to 10⁻⁵ mol/L; the 6801 extends one decade lower to 10⁻⁶ mol/L. Choose the 701 for convenient routine measurement; choose the 6801 when the lowest detection range is required.
Most pH and reference electrodes use KCl as the reference fill solution. For sodium ion measurement, KCl is avoided because potassium ions (K⁺) can diffuse from the reference junction into the sample and interfere with the sodium-sensitive glass membrane, causing measurement errors particularly at low sodium concentrations. Ammonium chloride (NH₄Cl) provides a stable reference junction without introducing potassium ions, preserving the selectivity of the sodium measurement.
Yes. The 701 uses a refillable reference system filled with 1.0 mol/L NH₄Cl solution. Periodically check the fill level and replenish with fresh 1.0 mol/L NH₄Cl solution as needed. Ensure the fill hole is open (plug loosened) during measurement to allow electrolyte flow through the reference junction. Keep the fill hole closed during storage to prevent evaporation.
The 701 is used for routine sodium ion measurement in power plant high-purity water monitoring, natural water and environmental water analysis, industrial process water quality control, university and research laboratory work, and any application requiring convenient single-electrode sodium ion measurement within the 10⁻¹ to 10⁻⁵ mol/L range.
Store the electrode upright with the fill hole plug closed and the electrode tip immersed in 1.0 mol/L NH₄Cl solution or a low-concentration sodium ion standard solution. Do not store in distilled water. Before use after storage, open the fill hole, rinse the electrode tip with distilled water and allow to equilibrate in a sodium standard solution before calibrating.
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