Electrical conductivity is the ability of a material to allow electrical charges to move freely, that is, to allow the passage of electrical current. Regarding water (and all other materials), this means that this electrical conductivity represents its ability to conduct electrical current. This notion is inversely proportional to that of electrical resistivity.

The commonly used unit of measurement is Siemens (S/cm), often expressed in micro-siemens / cm (µs / cm) or millisiemens (mS/cm).

The conductivity is directly proportional to the amount of solids (mineral salts and not organic matter) dissolved in the water. Thus, the higher the concentration of minerals and dissolved trace elements, the higher the conductivity. There is also a relationship with water hardness: soft water normally has low conductivity, and hard water has high conductivity.

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The electrical conductivity or, conversely, the resistivity of the water, gives a good indication of the overall mineralization and, at the same time, of the purity of this water.

Often when we look at the water quality label, the resistivity, or sometimes the conductivity, is indicated. These values are influenced by the ion content.

As a first approach, we can already point out that all continental waters naturally contain ions, in more or less quantity. But what exactly is an ion?

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The salts and minerals that generally cause salinity in the aqueous medium are therefore divided into cations and anions. Among the cations and anions identified in the waters, there are those that are qualified as major, because almost always present, such as calcium (Ca + 2) or bicarbonates (HCO3-), and miners, evidently present in low quantity and often the reflection of particular or polluted waters.

In the group of major cations, we find:

magnesium (Mg + 2),

calcium (Ca + 2),

sodium (Na +)

potassium (K +)

In the group of major anions, we find:

bicarbonates (HCO3-),

sulfates (SO4-2)

chlorides (Cl-)

These are the minerals that are generally also found in mineralized waters and that their "virtues" do for health.

It should also be remembered that the ionic activity of water varies with temperature. To take precise measurements, it is therefore necessary to take the temperature into account in the conductivity measurements. Standard temperatures are generally taken at 20 ° C.

https://naturolistique.fr/la-resistivite-de-l-eau-et-la-conductivite-de-l-eau/

https://beta-static.fishersci.com/content/dam/fishersci/en_US/documents/programs/scientific/technical-documents/white-papers/apha-conductivity-standard-methods-white-paper.pd

http://edgeanalytical.com/wp-content/uploads/Inorganic_SM2510.pdf

https://law.resource.org/pub/us/cfr/ibr/002/apha.method.2510.1992.html

Article Comparison of electrical conductivity calculation methods fo...

https://www.fondriest.com/environmental-measurements/parameters/water-quality/conductivity-salinity-tds/

To avoid uncertainties in the interpretation of the electrical conductivity of water varies from 1200 µS / cm to 1250 µS / cm, it should a priori be considered that it is a single sample. That said, there is no change in time and sampling procedure and that the sample was placed in a single vial and the measurement of conductivity was just after the sampling on the study site.

These conditions being met, it can be said analytically that this difference is not a problem. It may happen that the analyst used two different devices, in this case the difference may be due to the degree of sensitivity of each device. Or the measurement was with the same equipment, in this case a lack of agitation of the sample can be at the origin of the difference, a small solid particle, or the beginning of the weak of the batteries of the apparatus .

In my previous contributions, I first proceeded to define the electrical conductivity, the different ions that participate in its presence, the measurement methods based on references. The question now is, why should we interpret the electrical conductivity of water varies from 1200 µS / cm to 1250 µS / cm? Answering this question first refers to the need to know the use of this water. Indeed, the quality of water depends on its use.

In the European Union the recommended value for electrical conductivity in tap water is 400 µS / cm. In France, it varies from 180 - 1000 µS / cm. In the United States, it is between 50 and 800. If we must interpret the results expressed in your question in relation to the threshold values, we will say that 1200 µS / cm and 125 0 µS / cm are higher than the values, the service concerned will not be able to distribute this water through the taps of subscribers.

The Subject included in Physical Chemistry - Conductance of a Solution is basically dependent on mobility of ions = Reciprocal of resistance ( R ) .

C = 1/R . According to ohms law R = ( Row * L ) /A - Usual meanings . The Reciprocal of Row is called Specific condtance or Conductivity - Units - microS( mho ) for Conductance and for Conductivity the unit - micro S / cm . L/A - Cell Constant .