We've already mentioned the ORP value a few times, but what's behind it?
The short form “ORP” stands for “oxidation-reduction potential,” a measurement that gives an indication of the tendency of water to act as either an oxidizing or reducing agent. Discussions about ORP usually focus on the “O” and the “R” (oxidation and reduction). However, less detailed descriptions of the “P” (potential) component are seen.
While it is obvious that the ORP measurement, represented in units of millivolts (mV = 1/1000 volt), describes a certain type of electrical potential, we will now turn to the question of what the nature of this potential is and what is being measured voltage potential really says about the water.
By definition, voltage is “the measured difference in electrical potential energy per unit charge between two points”.
The phrase “between two points” is important. A single object cannot have “tension”. For example, although the battery in Figure 2 may be described as a “9 volt battery,” the battery itself does not have a “9 volt voltage.” The potential of nine volts exists only between the two terminals of the battery, the positive terminal, which has a deficiency of electrons, and the negative terminal, which has an excess of electrons.
In the same way that altitude relates to sea level and temperature relates to the freezing point of water, voltage always represents the potential difference between two points, a measured point and a second reference point. Referring again to Figure 1, these two “dots” can be seen, the platinum ORP sensor electrode and the internal reference electrode.
Voltage potential represents the ability to do a certain amount of work using electricity (the flow of electrons). A battery has the potential to do work (although it won't work if it's in a drawer). The work that can be done with it includes a variety of everyday things such as shining a flashlight or controlling a TV remote control. With a standard digital voltmeter (abbreviated: “DVM”) we can measure the stored potential of a battery.
Although the meter can tell us the electrical potential of the electrons stored in the battery, by its nature it cannot tell us whether the battery's charge is 100% or just 25%; it can make our flashlight shine for an hour or just a few seconds.
ORP measurements only measure “potential” and do not guarantee that a particular response will occur. Other factors such as temperature, activation energy and reaction rates must also be favorable.
In any case, when the battery is inserted into a device, it will release its "unknown amount" of stored electrons, which will operate the device at a potential difference of nine volts until that potential is exhausted.
When we talk about voltage potential and electrons, we are referring only to the tendency of electrons to move between species, and not to the amount of electrons that are transferred; the larger the measured potential, the greater this tendency. However, whether or not they are actually transferred, or how much is transferred when the battery is inserted into a circuit, depends on the circuit's resistance to the flow of electrons. It is important to note that the potential for electron transfer (work) shown by the ORP meter does not necessarily mean that this transfer will ever occur. For example, if the wire connecting the flashlight bulb to the battery rusted, the resistance of the circuit could become large enough that no matter how good the battery was, nine volts would not be enough to overcome the resistance.
Just as electrons in the battery must overcome the resistance of the circuit before they can flow, chemical reactions must be able to overcome a similar type of resistance.
This may potentially require energy from an external source (e.g. a catalyst) before they can take place.
Some less obvious forms of work are carried out within the human body, for example the neutralization of a free radical by an antioxidant.
Whether or not water with negative ORP can actually act as an antioxidant in the body depends not only on which agent is responsible for generating the negative redox potential, but also on the ability of the reaction of that antioxidant in question to produce special types of “chemical” resistance to overcome.
While in chemistry the term “potential” refers specifically to the voltage potential, in this context it also conveys a second meaning, namely that of “possibility”.
And as we have seen, while the negative ORP shows the potential for a reaction, other factors must also be favorable before the reaction can actually take place.
Excerpt from the book by Randy Sharpe: “The relationship between dissolved H2, pH and redox potential”
