DE2133419C - Measuring probe for determining the ion concentration in liquids - Google Patents

Description

2i

1. Measuring probe for determining the ion concentration in liquids, in particular for pH measurement, with a glass electrode, the ione-sensitive ι layer of which is applied to a metallic carrier material, characterized in that the ion-sensitive layer as a cover enamel layer (4, 4a, 4b) a base enamel layer (2) is melted on. w

2. Measuring probe according to claim 1, characterized in that an electrical conductor (5, 6) connected to the ion-sensitive cover enamel layer (4; 4a; 4b) for potential dissipation in a cover enamel layer (2) arranged above the electrically insulating base enamel layer (2). 3) is melted down.

3. Measuring probe according to claim 1, characterized in that the base enamel layer (2 ) is designed to be electrically conductive in the region of the ion-sensitive cover enamel layer (4: 4a; 4b).

4. Measuring probe according to one of the preceding claims, characterized in that two or more ion-sensitive, electrically insulated cover enamel layers (4a, 4b) with different ion specificities are provided.

5. Measuring probe according to claim 4, characterized in that one of the ion-sensitive cover enamel layers (4) immersed in a reference liquid (9) which is connected to a κι via a diaphragm (11) Measuring liquid is connected.

6. Measuring probe for the selective measurement of hydrogen ions according to one of the preceding claims 1 to 5, characterized in that the enamel of the ion-sensitive cover layer μ layer (4, 4α, 4b) has the following composition:

510 ₂ 60-75 mole percent; Na ₂ O 15-25 mole percent; CaO 5-15 mole percent: Li _; O 0-5 mole percent; ZnO 0-2 mole percent. 4 <i

7. Measuring probe for measuring alkali ion concentrations according to one of the preceding claims I to 5, characterized in that the enamel of the ion-sensitive cover enamel layer (4, 4a, 4b) has the following composition:

510 ₃ 60-75 mole percent; Na ₂ O 10-25 mole percent; CaO 0-3 mole percent; B ₂ O, 0-15 mole percent; Al ₂ O ₃ 0-12 mole percent.

expansion coefficient of glass and metal hairline cracks or even cause the glass to crack. In particular, the fusion of larger electrode glass membranes with metal has therefore hitherto been considered technically impracticable. (Kratz, "The Glass Electrode and Its Applications". Verlag Steinkopff, 1950, page 59).

It is also known, a metallic connection electrode, which is preferably made of copper, on the To oxidize the surface and to melt a layer of glass onto this oxide layer (German interpretation scripture 1,291,139). This is to achieve that through the diffusion of the oxide the directly the Connection electrode adjacent glass layers receives a thermal expansion coefficient between that of the metal and that of the further outer layer of glass in which no Oxide is diffused into it. Even if this desired effect occurs to a substantial extent should, even with this proposal, it does not seem possible to use larger electrode glass membranes To fuse metal without this, especially in the case of large temperature fluctuations and pressure Fluctuations Hairline cracks and other damage to the glass membrane occur.

It is therefore seen as a disadvantage of all known glass electrodes that they are not mechanically sufficient are accordingly stable, so that in particular an ongoing Measurement of the pH value in chemical apparatus with agitators, in which by overpressure, temperature Fluctuations and mechanical loads caused by the stirring effect occur, practically not possible.

It is therefore the object of the invention to provide a measuring to train probe of the type mentioned in such a way that not only over a long period of time a constant Potential jump between the ion-sensitive layer and the metallic carrier material and results in the highest possible adjustment speed, but also a largely mechanically stable and Impact measuring probe that can also be used with high mechanical loads. e.g. in Clicmieappanucn occur with agitators for production purposes.

This task is for a probe to determine the ion concentration in liquids, ins especially for pH measurement with a glass electrode whose ion-sensitive layer is on a metallic one Carrier material is applied, solved according to the invention in that the ion-sensitive layer as The top enamel layer is melted onto a base enamel layer.

Practical tests have surprisingly shown that with such an enamelled one Steel tube provided measuring probe a relatively high setting speed can be achieved, and that with a measurement over a period of a good week the deviation down to a pH value of 0.05 remained constant (without temperature correction). Measurements were also run through in which the temperature was changed to 80 'and then returned to the initial value. Here deviations were only found within the scope of the measurement accuracy.

Although it is possible in itself, make the electrode under the glass lying Grundcmailschicht by certain additives sufficiently electrically conductive / u so dal. ', The steel body. au) the email aiifecschmol

3 4

zen, can even serve to derive potential, be replaced where ion concentration measurements,

the potential derivation follows preferably through a rascnen i ^ rm. ", especially under high pressure.

electrical fluctuations or high temperatures in contact with the glass electrode

between the conductor that is to be introduced into the insulating enamel layer, e.g. in Chenueapparaien ιm

melted. The carrier metal of the enamel layer ι agitators, where previously because of the mechanical engineering

is earthed and thus serves as an electrical retainer for the well-known Kemc glass electrodes

shielding for the embedded conductor. Measurement or only a bypass measurement possible

A measuring probe according to the invention can be from the war. . \ λ η He

Arrangement of such a glass electrode together Another important advantage of this Meusonuc

with a common reference electrode. iü according to the invention then lies. daU with only one

For the selective measurement of different types of ions, rod-shaped measuring probe, the concentrations of different

with a measurement probe several verschiedenar Dener types of ions can be measured ^k ° ^nne n <° ^az ° -

• Age electrode glasses, which react to certain types of ions in chemical apparatuses, the number of doors MeuzwecKc

respond, limited to a metallic carrier material on jointed container nozzles

enamelled: e.g. two suitable η ists can be used.

■ er glass electrodes on a measuring probe at the same time. It is also anßese-

pH and pNa measurements are carried out. This means that these glass electrodes can be of any size

: Two or more electrometers are required for this, which can be produced. Thereby lam sen ucr

On the one hand, reduce the electrode resistance to a common common reference electrode as far as possible

tuide and on the other hand to the potential derivation of the 20 emails with high -specific resistance üieiur

.,!.:, j:, __ ..,: <· .... u .._ r- \ ij., "j"., "" ,, """-, j ,.» »oi ^ VoieVtroHpp are required as iiieiaro-

are locks. The measurements can also be used by means of denmatenal.

of a measuring point switch with only one electrode That for a glass electrode according to the hardness

., τ be carried out. on the one hand, usable glass enamel should be emc possible

If in a liquid wedge only the concentration 21 is a linear function between the ion concentration and the

tMiiion of a lonenitrt, z. B. the pH value, changes, has the associated potential value and on the other hand

> Il-Ii in an advantageous further development of the invention with the greatest possible change in potential per κ.υη / χη

, white different types of glass electrodes. which deliver under tration unit. ..

Have different sensitivities for ions, one for n-valent ions is the maximum " ^{! O} S" ^ e ™ -

Direct measurement of the ion concentration in question -. Tcntial change per decade of concentration

without connecting a common reference electrode Nernst factor 2.3 RT / nF determined (R = UasKonsun-

execute. An electrometer is measured directly. T absolute temperature, F- l-araday consian-

, ioii potential leads of the two glass electrodes ^ te). According to this, with water stolTions it is possible to heat / 3 ί

connected. achieved a theoretical slope of 59.1 mV / pH

Fine measuring probe according to the invention, which are without u. The steepnesses that can be achieved in practice

L, nc common reference electrode, but ion-selective ar- depend on the enamel composition and see below

cures, takes place preferably for measurements at high mostly smaller than the theoretical value. . ,,. ·,

Pressures and temperatures usage. This measurement determines the composition of the glass enamels

probe mainly carries. e.g. for pH measurements. according to the type of ion to be detected,

two glass electrodes, one of these glass electrodes, for example! are preferred for pH measurements

which is immersed in a liquid wedge, which is made of boron and aluminum.

a diaphragm connected to the measuring liquid

is. The part of the components immersed in the measuring liquid must be composed:

The measuring probe can, however, also have several different lvlnlnrnyent

fge glass electrodes with different sensitivity π SiO, 60 to 75 Mo percent

wedges door have ions, so that the concentrations Na _: O 15 to 2. ^ Mo perzen

several types of ion can be measured at the same time, CaO 5 to 13 JJo percent

be able. The measurements can also be Li ₂ OO to 5 Mo percent in succession

by switching an electrometer, ZnO O was stirred up to 2 mol%

on the one hand with the glass electrode in the in

Reference liquid and on the other hand with the different ml., Hinnen

iicn ion-smart glass electrodes in the measuring liquid Usable enamels for measurements of alkali ions

connected with Concentrations contain boron and / or aluminum.

A particular advantage of the measuring probe according to which you can have the following components:

Invention is to be seen in the fact that it is an unusual ", ι. ,, -, ν / rnt

lent high mechanical robustness compared to SiO 60 to 75 - "

Has known glass electrodes. It is not Na ₂ O IO up to 25 Mo ρ o; .en

only very open temperature limits by more than CnO u'V μΪ

100-C mödieh. but it exists, also know- B ₂ O, ^is *

Difficulty at high pressures. By attempt, .... UA, "his I- Molpro / .cnt

was also found to be contrary to known

ten glass electrodes with metal coating practically none!. ,, - ,,, ^ iHlirn Off

Long-term potential shifts occur. At Anhand then the Zochnun * .-:.,. «^ Spillen Au

A long-term test over a period of time Non luhrunpsbcp.elc should explain the! • .rdm-ng in more detail

(, Months delivered a glass electrode ingeniously.:- der Er <, s be. It shows M ^ snml.-

finding a constant potential. This K.wen.ra Γΐμ. 1 single angsschn.u duiLh unj measuring probe

Lions measuring probe made of enamelled metallic work according to the number. du- / usamnicn with a ubli

Stollen can therefore advantageously be used everywhere there, just Bu / ugsel · k'r <„lc \ erv ·: κΐΐ! ·, ι nnuci.

FIG. 2 shows a longitudinal section corresponding to FIG. 1 through a modified exemplary embodiment two different glass electrodes; and

F i g. 3 shows a longitudinal section through an exemplary embodiment with two glass electrodes of the same type from FIG which one dips into a reference liquid, the is connected to the measuring liquid via a diaphragm.

The steel body 1 shown in Fig. 1 is conventional With a base enamel layer 2 and a top enamel layer 3 enamelled. The base enamel layer 2 and the cover enamel layer 3 have a significantly lower electrical conductivity than a glass enamel one. Glass electrode 4, so that the glass electrode 4 from the steel body 1 is practically electrical is isolated. The Empil layers 2, 3, 4 can be applied in a manner known per se. Form of the steel body 1 as a carrier material for the glass electrode 4 is not essential per se. The steel body 1 can, for example, be a baffle or a baffle that is required anyway in an agitator tank Be a thermometer tube. The potential is dissipated via a conductor 5 embedded in the enamel layer, which is connected to the glass electrode 4. To measure the ion concentration in a measuring liquid 8 is a common reference electrode 6 in this exemplary embodiment necessary. Between the glass electrode 4 and the reference electrode 6 there is an ion concentration dependent voltage, which is displayed on a high-resistance voltmeter 7. In this exemplary embodiment, however, the melted-down conductor is then 5 not necessary if the base enamel layer 2 under the glass electrode 4 has a sufficient electrical Has conductivity, so that the potential is dissipated directly through a connection with the steel body 1 can be done.

The in Fig. The embodiment shown in FIG. 2 differs from that shown in FIG. 1 in that no conventional reference electrode is required because two different types of glass electrodes 4a and Ab are provided, which are electrically insulated by the surrounding insulating enamel layer. The potential is diverted through the two fused-in conductors 5, 6. Since the two glass electrodes 4a, Ab have different responses to ions, they supply a concentration-dependent voltage which is displayed by the measuring device 7.

This measuring method is suitable for those cases where only one type of ion changes its concentration, e.g. B.

ίο for pH measurements that are not disturbed by foreign ions will.

Since the two glass electrodes Aa, Ab have different sensitivities for ions, when using a conventional reference electrode 6,

π as in Fig. 1, two kinds of ions are selectively detected. For the selective measurement of several types of ions using a conventional reference electrode 6 can instead of two, several glass electrodes can also be applied to a measuring probe.

In the case of the FIG. 3, two glass electrodes 4 are electrically insulated from the steel bodies 1 or 1 a by a base enamel layer 2 and a cover enamel layer 3. The inner steel body 1 is surrounded by a tubular outer steel body \ a, in order to create a space for the reception of reference liquid. 9 The enamelled steel body 1 is mushroom-shaped at the lower end, so that a ground-joint diaphragm 11 can be provided between the adjoining enamelled surfaces of the two steel bodies 1, la, via which the reference liquid 9 communicates with a measuring liquid 10 in the agitator tank. With the help of the measuring device 7. the attached to the melted conductors 5, 6

3 'is closed. therefore the ion concentration in the measuring liquid can be determined.

A plurality of ion-selective glass electrodes can also be enamelled in isolation from one another on the outer steel body 1 α, thereby enabling a measurement of the

4 (i allow concentrations of different ions will.

1 sheet of drawings

Claims (1)

Patent claims: The invention relates to a measuring probe for determining the ion concentration in liquids, in particular for pH measurement, with a glass electrode, the ion-sensitive layer on a metallic Carrier material is applied. With known vacuum tubes for pH measurements, which are applied to a metallic support body, there is on the one hand the difficulty that No constant potential jump over a longer period of time / between the glass and the metal of the connection gap trodc results, and that on the other hand the glass unzurci accordingly adheres to the metal, so that temperature fluctuations result from the different thermal effects 20th