Platinum Plated Platinum Electrode as Standard Reference Electrode
THE standard reference electrode per definition!
Platinated Platinum Hydrogen Electrode
In the past, a platinum plated platinum electrode washed round with hydrogen gas in hydrochloric acid has established itself. The equilibrium voltage of this electrode was defined as 0.000 V at all temperatures under standard conditions:
Hydronium ion activity 1 mol/L (hydrochloric acid or sulphuric acid are used in practice)
Hydrogen gas 1.013 bar
Only then, the hydrogen electrode is designated as a standard hydrogen electrode. If the voltage differences between various metals in their metal salt solutions are measured against the standard hydrogen electrode, different voltages arise, which can be higher or lower than 0.000 V.
Electrochemical Series
The expected equilibrium potentials of different systems at standard conditions (25°C, metal ion activity 1 mol/L) are collated in the electrochemical series.
Metals with an equilibrium potential lower than 0 V are designated as ignoble.
If the equilibrium potentials are higher than 0 V the metals are designated as noble.
In accordance with the electrochemical series, equilibrium potentials can be specified not only for metals, but also for non-metals and their ions as well as ionic compounds and their charge reversals. If a reactant is oxidised, a reduction product is formed simultaneously. Conversely, an oxidation product is formed while a reactant is reduced. Thus, there are always redox couples.
The equilibrium potentials are a measure of the oxidation or reduction capacity. The more negative this potential is, the more easily the metals emit electrons. They are oxidised and thus function as a reducing agent.
The higher the potential, the more complicated they are to oxidise electrons. Instead, they are easier to reduce and thus function as an oxidant.
The expected voltages for various combinations of half-cells can be calculated from the standard potentials. Predictions about possible or impossible chemical reactions in aqueous solutions can be made. The convention E = E (right) – E (left) is authoritative for calculating the expected voltages.
Measuring Standard Potentials with the Hydrogen Electrode HydroFlex
The measuring of potentials happens almost without current. The electrode with the potential to be determined is connected to a reference electrode in an appropriate solution via a measuring instrument. Depending on the measuring conditions, special requirements are placed on the test cell itself. However, the measuring instrument used can also have an impact on the measurements. The input resistance of the measuring instruments used can, depending on the internal resistance of the reference electrode, affect or even falsify the potential measurement.
With commercially available reference electrodes, potential measurement is only currentless if the measuring instruments are of high-resistance. Otherwise, electrochemical conversions can happen.
The hydrogen reference electrode HydroFlex has a low internal resistance, so that handheld multimeters can be used for the potential measurement – as long as the system to be tested is also of low-resistance.
Would you like to learn more about our hydrogen reference electrodes HydroFlex and Mini-HydroFlex?
Hydrogen Reference Electrode HydroFlex
The platinum-hydrogen reference electrode is the first choice to measure potentials conforming to standards. Here you will find some general information about it.
Mini Hydrogen Reference Electrode Mini-HydroFlex
We have further developed and reduced the size of our hydrogen electrode HydroFlex for use in confined spaces. Here you will find some general information about our Mini-HydroFlex.
Use of the Hydrogen Electrodes HydroFlex and Mini-HydroFlex
Here you will find out more about the electrolytes and solutions in which our hydrogen reference electrodes can be used. Also learn more about the use of (Mini-)HydroFlex as a Reversible Hydrogen Electrode, Normal Hydrogen Electrode, and Standard Hydrogen Electrode.