Hi 5315 reference electrode – Hanna Instruments HI 5315 User Manual

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HI 5315 Reference Electrode

I.I.I.I.I. Introduction

Introduction

The Hanna HI 5315 reference electrode is a silver-silver
chloride double junction half-cell designed for use with ion
selective electrodes or pH sensors. The electrode utilizes a
quick flush sleeve design. The external reference electrolyte
chamber is refillable. The internal chamber is a perma-
nently filled, gel stabilized, chloride containing electrolyte.

IIIIIIIIII. Specifications

Specifications

Type:

Ag/AgCl

Operating Temperature:

0-85°C

Operating pH:

0 to 14 pH

Dimensions:

12 mm (OD) x 120 mm

insertion (0.47” x 4.72”)

Connection:

Banana Plug

Wetted Materials:

PEI

E°

SHE

(calculated):

0.238V

III.

III. Theory of operation

Theory of operation

A reference half-cell provides the electrolytic contact neces-

sary to permit a voltage gradient to be measured across a
measurement membrane, such as an ISE. A Ag/AgCl elec-
trode is the most common type of reference. The Nernst
expression for this type half-cell is expressed in the equa-
tion below. Note that the potential is a function of the
chloride concentration.

E=E

AgCl

- 0.059 log [Cl

-----

]

A chloride electrolyte completes the electrical circuit in the
inner half-cell. A bridge electrolyte is used as a buffer zone
between the inner half-cell and the sample. A small stable
liquid junction voltage is generated where the sample and
electrolyte come into contact. The size of this voltage, the
identity of the diffusing ions and how this barrier is formed
dictate stability. The barrier zone for this reference is a
narrow ring shaped opening formed between the outer
sleeve and the lower edge of the skirt shaped inner body.