SU785716A1 - Electrolyte composition for interior filling of glass electrode - Google Patents

Description

(5) ELECTROLYT - FOR INTERNAL FILLING OF GLASS ELECTRODES

The invention relates to physicochemical methods of analysis, in particular to pH meters. Electrolytes are known for the internal filling of glass electrodes based on 55% by weight of an aqueous solution of glycerin and acetic acid IJ. However, such electrolytes are unstable in time due to the volatility of acetic acid and do not provide a stable value of the isopotential coordinate of electrodes made on the basis of electrolyte data. The closest technical solution to the present invention is electrolytes used for internal filling of glass electrodes in a different set of components. chemical reagents in an aqueous 20% solution of glycerin 2. However, due to the low concentration of glycerin, the electrolyte freezes at a temperature of About 25 ° C. The aim of the invention is to create an electrolyte for the internal filling of glass electrodes, which ensures the frost resistance of the electrodes during transportation in winter to -25 ° C, and the improvement of the metrological characteristics of the electrodes (the coordinate value of the isopotential point should be 7 ± ± 0.3 pH, electrodes should show stable values of potentials in the range of pH scale at temperature differences from + 5 ° С to + 80 ° С). This is achieved by the fact that the proposed electrolyte contains chemical reagents in the following ratios, wt.%: Water .15.0-20.0 glycerin54.0-56.0 Potassium phosphate monosubstituted 6.7-6.8 Sodium phosphate disubstituted, anhydrous 7.0–7.2 Ammonium nitrate 7.5–8.5 Sodium chloride 3.5–3.6 Sol hydrochloride 0.8–3.0. Each of the listed chemical reagents gives a certain qualitative function to the electrolyte. A solution of glycerin in water lowers the freezing point of the electrolyte. The presence of a mixture of potassium phosphate monosubstituted and sodium phosphate dibasic anhydrous gives the electrolyte stability in pH. solution (buffering).

By adding hydrochloric acid, the required pH of the electrolyte is achieved to an accuracy of + 0.05 pH.

Ammonium nitrate is introduced to lower the freezing point of the electrolyte and to lower the electrical resistance of the electrolyte. Sodium chloride (chlorine ion) is introduced as the main component of the half cell system of the Ag (AgCl) Cl- chl-silver electrode.

Example. To obtain electrolyte, an experimental solution was prepared. The following composition, wt.%: Water 18,7

Glycerol55,0

Potassium phosphate. Single-substituted 6.8

Sodium phosphoric acid disubstituted anhydrous 7.1 AMMONIUM nitrate8, 0 Sodium chloride 3.5 Soloacid 0.9. The electrolyte obtained is subjected to the control by the pH value of the solution and by the potential of the silver-chloride half cell (E p / e) immersed in the electrolyte relative to the silver-chloride cTaHJtfapTHoro electrode, compared at + 20 ° C.

The data presented in table 1

Table

Continued table. one

The pH of the electrolyte should be 5.55 ± 0.05.

E P / E - the potential of the chlorine-silver half cell relative to the chlorine-silver standard comparison electrode should be equal to + 43 ± 3 mV. The fabricated test electrolyte was used to make an experimental test lot of electrodes of the type ESL-43-07 and ESL-63-07 according to GOST 5.2052j -73, which were subjected to control according to the test methods of this standard and TU 25.05.2-234-77.

The data obtained are summarized in table 2 and shown in the drawing.

The data table. 2 shows the full compliance of electrodes of the ECL-BZ 07 type with internal filling of the above-described electrolyte with respect to control parameters (potential, mV; slope, pH / mV, isopotential coordination of pH) to the requirements of GOST 5.2052-73 (TU 25.05.2234-77).

The figure shows the isopotential coordinate of pH, 7 at the intersection of the linear dependences of the measurement of the potential of the electo r pH of the solution at + 25 ° C, of the genus + 40 ° C,.

Climatic frost resistance tests have shown that in ECL-43-07 and ECL-BZ-07 electrolytes, internal filling freezes at a lower temperature. At the same time, all the electrodes characteristics of electrodes of type ЭСП-43-07 0 and ЭСЛ-63-07, which are controlled according to TU 25.05.2234-77, are preserved.

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Claims (2)

1. GOST 5.2036-73. Instructions for the preparation of solutions for filling glass electrodes, TU.1B 0.045.2604. 2.Patent of India 96412, cl. 126C (L.VI I I (6, published in 1964.