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mg KOH/g
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g/mol
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g/mol
25
mL
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mg KOH/g
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g/mol
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g/mol
25
mL
The Saponification Value (SV) calculator determines the number of milligrams of potassium hydroxide (KOH) required to completely saponify one gram of fat or oil. Saponification is the alkaline hydrolysis of ester bonds in triglycerides, producing glycerol and fatty acid salts (soap). The saponification value is a key analytical parameter in the oils and fats industry, providing direct information about the average molecular weight of the fatty acids present. Higher saponification values indicate shorter fatty acid chains (like in coconut oil, SV ~250), while lower values indicate longer chains (like in peanut oil, SV ~190). This measurement is used in quality control of edible oils, soap manufacturing, biodiesel production, and food science for verifying oil identity and detecting adulteration.
The saponification reaction converts a triglyceride into glycerol and three fatty acid salts:
$$\text{Triglyceride} + 3\,KOH \rightarrow \text{Glycerol} + 3\,\text{Fatty acid salts (soap)}$$
The saponification value is determined by a back-titration procedure:
$$SV = \frac{(V_{blank} - V_{sample}) \times N \times 56.1}{W}$$
where $$V_{blank}$$ is the KOH volume consumed in the blank test, $$V_{sample}$$ is the residual KOH volume after saponification, $$N$$ is the normality of KOH, 56.1 is the molecular weight of KOH, and $$W$$ is the sample weight in grams.
The average molecular weight of the triglyceride is:
$$MW_{avg} = \frac{3 \times 56100}{SV}$$
The factor 3 reflects that each triglyceride molecule reacts with 3 equivalents of KOH.
Typical saponification values for common oils: coconut oil 248-265 (short-chain fatty acids), palm oil 196-210, olive oil 184-196, soybean oil 189-195, castor oil 176-187, peanut oil 187-196. Values outside the expected range for a given oil indicate possible adulteration, degradation, or misidentification. The average molecular weight derived from SV provides insight into the fatty acid chain length distribution. The average fatty acid molecular weight is calculated by subtracting the glycerol backbone (MW = 92.09) from the triglyceride weight and dividing by three, then adding back the water of hydrolysis (18.015). This value typically ranges from 200-280 g/mol for common dietary fats.
Inputs
Results
SV = (18.8 × 0.5 × 56.1)/2.0 = 263.8 mg KOH/g. High SV confirms short-chain fatty acid predominance in coconut oil.
Inputs
Results
SV = (13.5 × 0.5 × 56.1)/2.0 = 189.3 mg KOH/g. Typical for olive oil, indicating predominantly long-chain (C18) fatty acids.
Saponification is the chemical reaction of a fat or oil with a strong base (NaOH or KOH) to produce glycerol and soap (fatty acid salts). The term comes from the Latin 'sapo' meaning soap. This reaction cleaves the ester bonds in triglycerides through alkaline hydrolysis.
KOH is preferred for analytical saponification value determination because it is more soluble in the ethanol-water mixture used as the reaction medium. NaOH is preferred for commercial soap making because sodium soaps are harder (bar soaps), while potassium soaps are softer (liquid soaps).
A high SV indicates that the fat contains predominantly short-chain fatty acids. Short chains have lower molecular weight, so more molecules are present per gram, requiring more KOH for complete saponification. Coconut oil (SV ~255) has many C12 and C14 fatty acids.
Soap makers use the SV to calculate the exact amount of NaOH or KOH needed to completely saponify a given weight of fat. This prevents unreacted lye (excess NaOH) in the final product. A slight excess of fat (superfatting, 5-8%) is often used for moisturizing properties.
SV measures the average chain length (how big the molecules are), while iodine value measures the degree of unsaturation (how many double bonds). Together, they characterize a fat or oil. For example, coconut oil has high SV (short chains) but low iodine value (saturated).
Yes. If an expensive oil like olive oil is adulterated with a cheaper oil, the SV will deviate from the expected range. Regulatory bodies like the Codex Alimentarius specify acceptable SV ranges for each oil type, enabling adulteration detection through routine testing.
The blank test runs the same procedure without the fat sample. It measures the total KOH available for reaction. The difference between blank and sample KOH volumes represents the KOH consumed by saponification of the fat, eliminating systematic errors.
Saponification requires heating to drive the reaction to completion, but the ethanol solvent would evaporate. Reflux condenses the vapors and returns them to the flask, maintaining constant volume and ensuring complete reaction. Typical reflux time is 1-2 hours.
Waxes have lower saponification values (typically 70-120) compared to fats (175-265) because wax esters consist of long-chain fatty acids esterified with long-chain fatty alcohols, resulting in very high molecular weights and fewer ester bonds per gram.
Free fatty acids (FFA) also react with KOH during saponification and are included in the SV measurement. If you need to determine only the ester bonds, subtract the acid value (which measures only FFA) from the saponification value to get the ester value.
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