124.36
g I2/100 g
24.5
mL
0.3109
g
9.8
meq/g
124.36
g I2/100 g
24.5
mL
0.3109
g
9.8
meq/g
The Iodine Value (IV) calculator determines the degree of unsaturation of fats, oils, and waxes by measuring the grams of iodine absorbed per 100 grams of sample. Iodine adds across carbon-carbon double bonds in unsaturated fatty acids, so the iodine value is directly proportional to the number of C=C double bonds present. Highly unsaturated oils like linseed oil have high iodine values (170-204), while saturated fats like coconut oil have very low values (7-12). The iodine value is one of the most widely used quality parameters in the edible oil industry, paint and coatings formulation, biodiesel production, and oleochemical manufacturing. It classifies oils as drying (IV > 130), semi-drying (IV 100-130), or non-drying (IV < 100) — a critical distinction for paint and varnish applications.
The Wijs method (most common) adds excess iodine monochloride (ICl) to the sample dissolved in solvent. ICl adds across double bonds:
$$-CH=CH- + ICl \rightarrow -CHI-CHCl-$$
The excess unreacted ICl is converted to I₂ by adding potassium iodide (KI), then titrated with sodium thiosulfate (Na₂S₂O₃):
$$I_2 + 2\,Na_2S_2O_3 \rightarrow 2\,NaI + Na_2S_4O_6$$
The iodine value is calculated as:
$$IV = \frac{(V_{blank} - V_{sample}) \times N \times 12.69}{W}$$
where $$V_{blank}$$ and $$V_{sample}$$ are the thiosulfate volumes for the blank and sample respectively, $$N$$ is the normality of the thiosulfate solution, 12.69 is the factor (half the atomic weight of iodine, $$126.9/10$$), and $$W$$ is the sample weight in grams. The result is expressed as grams of I₂ absorbed per 100 grams of fat.
Common iodine values: coconut oil 7-12 (highly saturated), palm oil 44-58, olive oil 75-94, sunflower oil 118-141, soybean oil 120-143, linseed oil 170-204 (highly unsaturated). Values outside the expected range indicate adulteration, oxidation, or hydrogenation. The approximate double bonds per molecule is estimated assuming an average C18 fatty acid (oleic acid MW = 282 g/mol). Oleic acid (one double bond) has a theoretical IV of 89.9, linoleic acid (two double bonds) has 181.0, and linolenic acid (three double bonds) has 273.5. In the paint industry, oils with IV > 130 are classified as drying oils suitable for paints and varnishes.
Inputs
Results
IV = (24.5 × 0.1 × 12.69)/0.25 = 124.4 g I2/100g. Falls within the expected range for soybean oil (120-143).
Inputs
Results
IV = (1.4 × 0.1 × 12.69)/0.25 = 7.1 g I2/100g. Very low IV confirms coconut oil is predominantly saturated.
Iodine value measures the degree of unsaturation (number of C=C double bonds) in fats and oils. It is defined as the grams of iodine absorbed per 100 grams of sample. Higher values indicate more double bonds, meaning the fat is more unsaturated.
The Wijs method uses ICl (iodine monochloride) as the halogenating reagent because it reacts more specifically with double bonds than I2 alone. However, the result is expressed in terms of equivalent iodine mass for standardization and historical consistency.
Drying oils (IV > 130) polymerize when exposed to air, forming a hard film — ideal for paints. Semi-drying oils (IV 100-130) partially dry. Non-drying oils (IV < 100) remain liquid and are used in cooking and lubrication. Linseed oil is the classic drying oil.
Hydrogenation converts double bonds to single bonds by adding H2, directly reducing the iodine value. Partially hydrogenated oils have lower IV than the original oil. This is used to convert liquid oils into solid fats (margarine), though the process can create trans fats.
Yes. Oxidation of double bonds forms peroxides, epoxides, and other products that no longer react with iodine. Oxidized oils show lower iodine values than fresh oils. A decrease in IV during storage indicates oxidative degradation of the oil.
The factor 12.69 = 126.9/10 converts milliequivalents of thiosulfate to grams of iodine per 100g of sample. Since 1 mole of I2 reacts with 2 equivalents of thiosulfate, and the atomic weight of I is 126.9, the factor accounts for this stoichiometry and the per-100g convention.
The Hanus method uses iodine monobromide (IBr) instead of ICl as the halogenating agent. It gives slightly different results from the Wijs method. Both methods are accepted by AOCS and AOAC standards, but the Wijs method is more commonly used internationally.
The reaction between ICl and double bonds is temperature-sensitive. The standard method specifies a reaction time of 30 minutes in the dark at 25°C. Higher temperatures can cause substitution reactions (rather than addition), leading to erroneously high results.
Yes. If the fatty acid composition is known, the theoretical IV can be calculated from the number of double bonds in each fatty acid and their weight fractions: IV = Σ(fi × dbi × 253.8/MWi × 100), where fi is the weight fraction, dbi is the double bond count, and MWi is the fatty acid molecular weight.
The European biodiesel standard EN 14214 limits iodine value to 120 g I2/100g to ensure oxidative stability. Highly unsaturated oils (high IV) are more prone to oxidation and polymerization, which can cause engine deposits and filter clogging in diesel engines.
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