SU1131843A1 - Electrode glass - Google Patents

Description

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CO. The invention relates to the production of special electrod glass for potentiometric measurements of the activity of hydrogen ions and is intended for use in microbiological, chemical and pharmaceutical, food and medical industries, which are based on fermentative biosynthesis processes. Electrode-glass 1 is known, including, wt%: SiOj 64-71; LijO 20-31; Disease 2-4; MgO 3-5. However, electrodes made on the basis of this glass do not give stable characteristics after steam treatment, even under relatively mild sterilization conditions, namely 120 ° C for 1 hour. As a result, the error in determining the acidity of the medium considerably exceeds the practical value of ± 0.2 units .rn The closest to the proposed by the technical essence and the achieved result is the electrode glass, containing, in wt.%: Srg. 5056.5 CszO. 6.5-8.5 NdO3. 17-19 An electrode based on this glass withstands 30 direct sterilization cycles. The cycle duration varies with the sterilization temperature. At 120 ° C, the duration of one cycle is 1 hour, at 150 ° C - 10 minutes 2. The disadvantage of this glass is that with an increase in steam treatment time (with an increase in the duration of one sterilization cycle), for example, at a maximum sterilization temperature of 150 ° C 2 hours, electrodes based on this glass do not give stable characteristics, which significantly reduces the measurement accuracy and in fact does not allow using them to control the pH. The purpose of the invention is to increase the accuracy of pH measurement after acute sterilization. ferry. This goal is achieved by the fact that electrode glass, including SiOz, LizO additionally contains MpO and, at least. one oxide from the group of CaO, MgO, BaO, in the following ratio of components, wt.%: SiOz63-77.5 LiiO12.5-15.5 MnO. 0.5-1.5 at least one oxide from the group CaO, MgO, BaO7.5-23.0 The specific compositions of the glasses are given in Table 1. Table

To obtain glass, chemically pure powder reagents in the form of oxides and carbonate salts, previously dried to a constant weight, are used.

Synthesis is carried out in a platinum crucible in furnaces with carborundum electric heaters. The mixture melts at 200 ° C. Next, the furnace temperature is raised to HSOC and maintain the glass melt at this temperature for 2 hours.

In the process of cooking glass melt mixed at least 2 times. After completion of the synthesis, glass is produced in the form of daddies.

The deviation of the potentials and the electrical resistance of the electrodes after treatment at 145 ° C with live steam after 1 h of incubation in a controlled environment are presented in Table. 2

The composition of the glass is LEM. P. MOM 2. 3 4 5 6 Prototype

Electrode based on the proposed glass has a hydrogen function ranging from O to 10.5 - 11.5 pH at 25 ° C and from O to 9.5 pH at 40 s against a background of sodium ions with a concentration of 1 mol / l, withstands more severe conditions of sterilization by acute steam at 50 ° C and a treatment cycle duration of 2 hours. The steepness of the hydrogen function of the electrodes before and after sterilization corresponds to the theoretical value. The higher resistance of the glass to the effects of steam makes it possible to measure the acidity of the medium with a smaller error, which for 10 cycles of treatment does not exceed -H0.1 pH (+6 mV).

From tab. 2, it can be seen that the deviation of the potential of the electrode after the treatment with nar

Table Sterilization Cycle Number

the stationary value (obtained previously in the calibration process with standard buffer solutions) is significantly less than that of the known glass. The electrical resistance of the electrodes from the specified glass is prior to sterilization at 250-400.Ohm and does not exceed the permissible value (1000 MΩ) after 10 sterilization cycles.

The proposed electrode glass compositions dramatically increase the accuracy of pH measurement (10 times) after exposure to direct steam, both by shortening the relaxation time of the potentials of the glass electrodes and by more stable characteristics during repeated sterilization. E, mV R.MOn, mV R,

Claims (1)

ELECTRODE GLASS, including SiOt, Li ₂ O, characterized in that, in order to increase the accuracy of measuring pH after sterilization with direct steam, it additionally contains MnO and at least one oxide · from the group of CaO, MgO, BaO, at the following ratio of components, wt.%: SiO ₂ 63-77.5 Li ₂ O 12.5-15.5 MnO 0.5-1.5 at least one oxide from the group CaO, MdO, BaO 7.5-23.0>