GIFSQ Tools · Module 2 — Food Chemistry & Physicochemical Testing · Tool 28 of 500
Mohr titration: titrate the chloride in a food sample with standard silver nitrate and get the salt as sodium chloride, in percent and in mg/kg. AOAC 937.09.
Try sample values — fills the form with the worked example below.
–
Salt as NaCl (%)
–
Salt (mg/kg)
–
Net titration (mL)
Equation: Salt as NaCl % = (V − Vblank) × N × 0.05844 × 100 ÷ m, where V is the titration volume in mL, N the AgNO3 normality, and m the sample weight in g. Salt in mg/kg = % × 10 000.
Method: AOAC 937.09 (salt in foods, Mohr titration) — chloride is titrated with standard silver nitrate to the potassium chromate end point. One mL of 1 N AgNO3 reacts with 0.05844 g of NaCl.
Assumptions: all of the chloride in the sample is sodium chloride; the AgNO3 is standardised; the end point is the first lasting red-brown colour.
Limitations: other chlorides (such as potassium chloride) are counted as sodium chloride, so the result is salt as NaCl, not sodium alone. Dark or cloudy samples hide the end point — use a potentiometric end point instead.
Rounding: salt % to 2 decimal places; mg/kg to the nearest whole number.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Method: AOAC 937.09 (salt in foods, Mohr titration) — chloride is titrated with standard silver nitrate to the potassium chromate end point. One mL of 1 N AgNO3 reacts with 0.05844 g of NaCl.
Assumptions: all of the chloride in the sample is sodium chloride; the AgNO3 is standardised; the end point is the first lasting red-brown colour.
Limitations: other chlorides (such as potassium chloride) are counted as sodium chloride, so the result is salt as NaCl, not sodium alone. Dark or cloudy samples hide the end point — use a potentiometric end point instead.
Rounding: salt % to 2 decimal places; mg/kg to the nearest whole number.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Worked example: 5.00 g of cheese titrated with 12.50 mL of 0.1 N AgNO3, blank 0.10 mL. Net titre = 12.40 mL. Salt = 12.40 × 0.1 × 0.05844 × 100 ÷ 5.00 = 1.45 % as NaCl, or 14,493 mg/kg.
Enter values above to see results.
Typical salt: bread 1.0–1.5 %, cheese 1.2–2.5 %, cured ham 3–5 %, soy sauce 15–18 %, fresh milk 0.1 %. Salt % × 0.393 gives sodium %; sodium × 2.54 gives salt %. Tool 28 of 500 — GIFSQ
