/ TECHNICAL AUXILIARY MATERIALS / Cleaning products / Alkaline cleaning agents

T-741.03.032 [2024-08] Alkaline cleaning agents containing carbonate - sodium hydroxide and soda

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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Soda is used in breweries as a cleaning agent and is sometimes required for the production of bottle-cleaning lyes.

There are two forms on the market:

a) calcined soda (anhydrous soda) = 100 % Na₂CO₃

b) crystal soda = Na₂CO₃ · 10 H₂O = 37.06 % Na₂CO₃

Caustic soda, also known as lye or soapstone, is raw caustic soda (NaOH) that contains varying amounts of soda ash (Na₂CO₃). The higher the NaOH content, the better the product. It is mainly used in the self-production of bottle-cleaning lye.

alkaline cleaners

carbonates

cleaning agents

cleaning concentrates

Application/Purpose

Determination of the concentration of alkaline cleaners in sodium hydroxide (NaOH) and soda (Na₂CO₃).

Scope of Application

All alkaline cleaning solutions or "batch solutions" that contain soda (Na₂CO₃) as a cleaning component in addition to sodium hydroxide (NaOH).

Principle

If the alkaline solution is likely to be strongly influenced by carbonic acid or if the cleaning solutions are used over a longer period of time ('batch cleaning'), the degree of carbonation must be taken into account to determine the exact concentration or pH value, as the resulting soda has a greatly reduced cleaning effect, but simulates an excessively high concentration of the active cleaning agent.

Determine the sodium hydroxide (NaOH) content of the detergent solution with an acid solution (HCl or H₂SO₄) with corresponding normality up to the color change of phenolphthalein (pH 8.2).

NaOH + HCl → NaCl + H₂O colorless against phenolphthalein

2 NaOH + H₂SO₄ → Na₂SO₄ + 2 H₂O

Determination of the soda ash (Na₂CO₃) content of the detergent solution with an acid solution (HCl or H₂SO₄) with corresponding normality up to the color change from methyl orange (pH 4.3).

Na₂CO₃ + HCl → NaHCO₃ + NaCl

NaHCO₃ + HCl → NaCl + H₂O + CO₂ yellowish brown against methyl orange

2 Na₂CO₃ + H₂SO₄ → 2 NaHCO₃ + Na₂SO₄

2 NaHCO₃ + H₂SO₄ → 2 Na₂SO₄ + H₂O + 2 CO₂