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Water Analysis - 17042 15

WATER ANALYSIS

The pH Value

The pH value is a logarithmic measure for the concentration of the H ions in ahydrous solution and indicates, by a numerical value, whether the solution has an acid, neutral or alkaline reaction.The pH scale ranges from pH0 to pH14, pH7 is neutral.The further the pH value deviates from 7, the more aggressive the sample is. The acidic or alkaline effect will increase by the factor 10 per pH unit. The illustration on the left shows some examples for pH values of typicalsubstances.

The Redox Potential

The level of the Redox potential (measured in mV) indicates the strength of an oxidising or reducing reaction of a measuring solution.A negative voltage value means that the solution has reducing properties compared to a standard hydrogen electrode. A positive valueindicates that the solution has an oxidising effect.As the extermination of microorganisms (disinfection) is directly related to the strength of the oxidation (e.g. of chlorine) the Redoxpotential is successfully being used for monitoring disinfection processes, e.g. in swimming baths. However, redox measurements arealso performed for controlling the denitrification of waste waters (redox break point determination) at the detoxification in galvanicplants and for monitoring multiple chemical processes (e.g. cyanide oxidation or chromate reduction).

ALMEMO

®

pH and Redox Measurement

By using reference solutions the calibration of pH and redox probes can be started with the push of a button. As the adjustment isstored in the ALMEMO
® connector, the probe can also be used with other devices. If ALMEMO
® devices with several input sockets areused, it is even possible to connect more probes with individual adjustments. The calculation of the pH value is based on the electrodesteepness at 25°C. If the temperature of the measuring medium largely deviates from the reference temperature, it is possible for allALMEMO
® devices to perform a temperature compensation.

The Electrical Conductivity

The conductivity (unit S/m = Siemens/meter) is a measure for the ion concentration in a measuring solution. It is proportional to the salt, acid or base content in the measuring solution. High-purity waters have a conductivity of approx. 0.05 µ S/cm (at 25°C), natural watersapprox. 100 to 1000mS/m, some bases (e.g. potassium hydroxide solutions) up to slightly more than 1000mS/cm. The diagram shows further examples of hydrous solutions relevant formeasurements.In practice, the conductivity measurement is used for monitoring plants, forproducing of high-purity waters or for determining the salinity of sea water.

15.02

01/2007 We reserve the right to make technical changes.