T-741.06.032 [2024-08] Alkaline cleaning agents containing aluminum - sodium hydroxide, aluminum, 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.

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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.

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Since the usual determination of the concentration or the p-value of a cleaning solution by dissolved aluminium shows incorrect results, the following determination is carried out, which simultaneously enables the concentration of aluminium to be specified.

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.

Application/Purpose

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

Scope of Application

All alkaline cleaning solutions or "stack solutions" that contain dissolved aluminum (Al3+) and/or soda (Na2CO3) in addition to sodium hydroxide (NaOH) as a cleaning component.

Principle

The sodium hydroxide bound as aluminate and titrated in the p-value determination is calculated by subsequent determination of the aluminum and deducted, as it is no longer available for purification.

The aluminum determination itself is based on the reaction between aluminum hydroxide and sodium fluoride, in which sodium hydroxide is released and thus serves as a measure for calculating the aluminum.

Titration against methyl orange instead of the Tashiro indicator leads to incorrect results. When sodium fluorif (NaF) is added to the alkaline solution, hydrofluoric acid (HF) is formed. The hydrofluoric acid destroys the methyl orange indicator.

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