/ TECHNICAL AUXILIARY MATERIALS / Cleaning products / Alkaline cleaning agents

T-741.02.032 [2024-08] Alkaline cleaning agents - quicklime (CaO) or sodium hydroxide without 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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Quicklime is used in breweries as a cleaning agent and in brewing and boiler water treatment. A prerequisite for representative results is that the test material corresponds to the cross-section sample.

alkaline cleaners

cleaning agents

cleaning concentrates

Application/Purpose

Determination of the concentration of alkaline cleaners on quicklime (CaO) and sodium hydroxide (NaOH) without soda (Na₂CO₃).

Scope of Application

All alkaline cleaners, such as quicklime or sodium hydroxide without soda.

(Technical) sodium hydroxide, caustic soda, soda ash and their aqueous solutions always contain more or less carbonates.

With higher carbonate contents, the following methods can be used:

T-741.03.032 Alkaline cleaning agents containing carbonate - sodium hydroxide and soda

T-741.04.032 Alkaline cleaning agents containing carbonate in the presence of phosphates and soiling - sodium hydroxide and soda

T-741.06.032 Alkaline cleaning agents containing aluminum - sodium hydroxide, aluminum, soda

The proportion of carbonate that is not effective for cleaning can be determined.

Principle

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

Quicklime

CaO + H₂O	→ Ca(OH)₂
Ca(OH)₂ + 2 HCl	→ CaCl₂ + H₂O	colorless against phenolphthalein
Ca(OH)₂ + H₂SO₄	→ CaSO₄ + 2 H₂O	colorless against phenolphthalein

Sodium hydroxide

NaOH + HCl	→ NaCl + H₂O	colorless against phenolphthalein
2 NaOH + H₂SO₄	→ Na₂SO₄ + 2 H₂O	colorless against phenolphthalein