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The aliquot of an extract of malt is added to a buffered starch solution and allowed to stand for exactly 30 min at 20 °C. Then, the maltose – formed primarily from the starch through the action of the β-amylase – is measured using iodine and is determined according to the following chemical reaction:

The analysis involves a reaction with N,N-diethyl-1,4-phenylenediamine (DPD), which forms a compound possessing a red color at a pH of 6.2–6.5. The solution is titrated with an ammonium iron(II) sulfate standard solution until the red color disappears. Total chlorine is measured through the addition of potassium iodide, of which a known amount in excess of that required is added to the solution in advance.

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.

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.

Additives containing phosphoric acid in particular - but also other types of additive - can simulate a more or less significant Na₂CO₃ content due to their buffering effect. Firstly, phosphoric acid significantly blunts the p-value by forming sodium phosphate (Na₃PO₄) and secondly, the difference between the m-value and the p-value is increased because sodium dihydrogen phosphate (NaH₂PO₄) is largely formed from disodium hydrogen phosphate (Na₂HPO₄) in the pH range 8.2 to 4.3. The same applies - but to a lesser extent due to the molecular sizes - to typical phosphonic acids or their salts, but not, for example, to most surfactants.

To determine the exact concentration or pH value, the content of buffering substances - phosphates and impurities - must be taken into account in addition to the degree of carbonation, as otherwise the concentration of the active cleaning agent will be too high.

Determination of the p-value 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

The most important step is the expulsion of CO₂. This is to ensure that no more hydrogen carbonates or carbonates can form during the subsequent back titration with NaOH. For this purpose, a significant acidification below pH 4.3 must be carried out with acid in order to be able to drive out CO₂ using an inert gas.

The proportion of buffering substances can then be determined by back titration with NaOH to pH 4.3 or 8.2.

Through the addition of a sodium hydroxide solution, the carbon dioxide in beer becomes bound as sodium hydrogen carbonate or sodium carbonate. Sulfuric acid is added to an aliquot of the beer treated with sodium hydroxide. This causes the carbon dioxide to be released again, after which a stream of air conducts the carbon dioxide into a barium hydroxide solution. Through titration of the excess barium hydroxide, the carbon dioxide content of the beer can be determined [1].