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T-740.01.041 [2024-08] Electrolytic conductivity of acidic and alkaline cleaning agents

Ready-made cleaning agents are composed of a large number of different components. The analysis of individual components is irrelevant in practice, and it is usually sufficient to determine the alkaline or acid-reacting components by summary analysis. The manufacturers of cleaning agents and disinfectants specify so-called titration factors in the operating instructions for the individualproducts, which are used to calculate the concentration in percent by volume or weight.

For products that are marketed as liquid concentrates, both factors - both for volume and weight percentages - are printed, as the products are both titrated and weighed by the consumer.

The titration factor (TF) is the reciprocal of the amount of standard solution (HCI or NaOH) in ml, which must be used to titrate a certain volume of exactly 1 % solution of a detergent.
TF × ml consumption = GG-% product in solution

In practice, there are various different templates of the cleaning solutions to be determined and normalities of the standard solutions in use: generally 10, 50 or 100 ml, which are diluted with 0.1 mol/l (0.1 N), 0.5 mol/l (0.5 N) or 1 mol/l (1.0 N) hydrochloric acid or sodium hydroxide solution against phenolphthalein or methyl orange. The resulting consumption of hydrochloric acid or sodium hydroxide solution in ml multiplied by the factor specified by the manufacturer gives the concentration of the cleaning solution in percent by volume or weight. For highly alkaline cleaning solutions, templates of 5 ml are also suggested. Some cleaning and disinfectant manufacturers also prescribe sulphuric acid or acetic acid instead of hydrochloric acid and recommend a certain normality, which makes further calculation unnecessary, so that the ml of acid used gives the concentration of the cleaning solution directly.

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When using alkaline cleaning solution, a reaction with carbonates from the air or from contamination can occur. This is particularly relevant (but not limited) for brewery and beverage plants due to the higher amount of CO₂ in the atmosphere. If an effect of carbonic acid on the caustic is expected or if the cleaning solution is used over a longer period of time, it is necessary to consider the degree of carbonation to determine the exact concentration.

This is because the cleaning effect of sodium carbonate (Na₂CO₃) is greatly reduced, but the titration simulates a high concentration of the active cleaning agent (NaOH).

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Acidic cleaners are cleaning agents that contain acidic ingredients such as citric acid, acetic acid or phosphoric acid to dissolve and remove stubborn soiling. They are particularly effective at removing limescale, rust, mineral deposits and other acid-soluble residues.

alkaline cleaners

acidic cleaners

cleaning agents

cleaning concentrates

Application/Purpose

Determination of the concentration of sodium hydroxide (NaOH) or soda (Na₂CO₃) of alkaline cleaners and determination of the acid concentration of acid cleaners by means of conductivity measurement.

Scope of Application

All alkaline or acidic cleaning solutions.

Principle

The main components of alkaline and acidic detergent solutions are strong electrolytes with a high degree of dissociation. If an electric field is applied in an aqueous system, the ions take over the current transport. This depends, among other things, on the concentration of the electrolyte. By measuring a defined value - the so-called specific conductivity - a linear dependency is given in the concentration range commonly used in cleaning practice and the concentration can be easily determined. The specific conductivity is specified in the unit Siemens or millisiemens per centimeter (S/cm; mS/cm).