All alkaline or acidic cleaning solutions.
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).
Determination of the concentration of active ingredients in alkaline cleaners.
All alkaline cleaning solutions.
Alkaline cleaning solutions, especially for automatic bottle cleaning, consist of sodium hydroxide and so-called active ingredient concentrates. Concentration losses caused by carryover or carbonization can be determined by determining the alkaline component in accordance with
T-740.01.041 Electrolytic conductivity of acidic and alkaline cleaning agents
T-741.02.032 Alkaline cleaning agents - sodium hydroxide only
T-741.03.032 Alkaline cleaning agents containing carbonate - sodium hydroxide and soda
T-741.04.023 Alkaline cleaning agents containing carbonate in the presence of phosphates and soiling - sodium hydroxide and soda
T-741.05.032 Alkaline cleaning agents containing aluminum - sodium hydroxide, aluminum
T-741.06.032 Alkaline cleaning agents containing aluminum - sodium hydroxide, aluminum, soda
can be controlled. However, the active ingredient concentrates are only recorded if it is ensured that the required concentration of the desired active ingredient has been added or dosed using appropriate dosing equipment (proportional dosing). If this is not the case, i.e. if the active ingredient concentrates are prepared and dosed manually, a separate check of the active ingredient concentration is advisable. The determination methods are very different and are specific to a particular active ingredient concentrate*. The method should be requested from the manufacturer.
* e.g. P 3-stabilon; Henkel Hygiene GmbH, D-40554 Düsseldorf, https://www.henkel.de/
All alkaline cleaning solutions or "stack solutions" that contain sodium hydroxide (NaOH) as well as dissolved aluminum and/or soda (Na2CO3) in addition to free chlorine.
Alkaline cleaning agents and disinfectants containing chlorine can be determined by their alkalinity concentration. The chlorine present destroys most indicators by oxidation. Before adding the indicator, the chlorine must be eliminated by adding sodium thiosulphate to the sample.
Determination of the concentration of alkaline cleaners in sodium hydroxide (NaOH) and soda (Na2CO3).
All alkaline cleaning solutions or "batch solutions" that contain soda (Na2CO3) as a cleaning component in addition to sodium hydroxide (NaOH).
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
Determination of the concentration of alkaline cleaners in sodium hydroxide (NaOH) and aluminum (Al).
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.
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.
Carbonates interfering with the titration are precipitated with Ba2+ ions.
Determination of the concentration of alkaline cleaners in sodium hydroxide (NaOH), soda (Na2CO3) and aluminum (Al).
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.
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.