Industrial chemistry analysis plays a pivotal role in ensuring quality control and product standardization across various manufacturing sectors in Kenya, including pharmaceuticals, textiles, and leather processing. Among the essential analytical tests in this field is the determination of the copper number, a key parameter in assessing the degree of unsaturation in fats and oils. This chapter focuses on the calculation of the copper number, a procedure that informs quality assurance professionals about the oxidative stability and shelf life of industrial products containing fats and oils, which are widely used in Kenya’s agro-processing and cosmetic industries.

7.1 Calculate copper number

The calculation of the copper number is an important analytical technique used to quantify the amount of unsaturated compounds, primarily unsaturated fatty acids, in fats and oils. This parameter is crucial in the leather industry, food processing, and cosmetic manufacturing, where unsaturation levels affect product quality and stability. In Kenya, industries such as leather tanning at cooperatives and edible oil refining plants routinely employ this test to monitor raw material quality and finished product standards.

7.1.1 Principle and Definition of Copper Number

The copper number is defined as the amount of copper (in milligrams) that reacts with 100 grams of fat or oil. It measures the degree of unsaturation by quantifying the copper salts that combine with double bonds present in unsaturated fatty acids. The test relies on the formation of a colored complex between copper ions and the unsaturated bonds, which can be quantified by titration or spectrophotometry.

Principle of Copper Number

• Reaction with Unsaturated Bonds: Copper (II) salts react specifically with the double bonds in unsaturated fatty acids, forming a complex that indicates the extent of unsaturation.
• Quantitative Measure: The amount of copper consumed in the reaction correlates directly with the number of double bonds, allowing quantification of unsaturation.
• Indicator of Oxidative Stability: Higher copper numbers suggest greater unsaturation, which typically corresponds to lower oxidative stability and shorter shelf life.
• Application in Quality Control: This measurement helps industries adjust processing parameters to ensure product consistency and compliance with Kenyan industrial standards.
• Relevance to Industrial Chemistry: Understanding copper number assists in selecting appropriate antioxidants and processing conditions for fats and oils in products such as leather conditioners and edible oils.

7.1.2 Equipment and Reagents Required for Copper Number Determination

Accurate determination of the copper number requires specific laboratory apparatus and reagents that are standardized for industrial chemical analysis.

• Use the analytical balance to weigh a precise amount of fat or oil sample.
• Prepare copper acetate solution freshly and standardize before use to ensure accuracy.
• Titrate with sodium thiosulphate to determine the amount of unreacted copper, enabling calculation of copper consumed.
• Maintain clean glassware to avoid contamination that could affect titration end points.
• Store reagents in tightly closed containers to prevent degradation or contamination.

7.1.3 Procedure for Determining Copper Number

The determination of the copper number involves a series of carefully controlled steps to ensure accuracy and repeatability. The procedure is widely adopted in Kenyan industrial laboratories for quality assurance in sectors such as the food industry and leather manufacturing.

1. Accurately weigh approximately 5 grams of the fat or oil sample using an analytical balance and transfer it into a clean conical flask.
2. Add 50 mL of 0.1 M copper acetate solution to the flask containing the sample.
3. Stir the mixture thoroughly to ensure complete reaction between copper ions and unsaturated bonds; allow the reaction to proceed for 30 minutes at room temperature.
4. Titrate the excess copper acetate solution with 0.1 M sodium thiosulphate solution using a burette until the endpoint is reached, indicated by a color change.
5. Record the volume of sodium thiosulphate used to neutralize the unreacted copper ions.
6. Repeat the procedure with a blank sample containing no fat or oil to determine the baseline volume of sodium thiosulphate required.

7.1.4 Calculation and Interpretation of Copper Number Results

The calculation of the copper number is based on the volume difference between the blank and the sample titrations, reflecting the amount of copper that reacted with unsaturated fatty acids.

Calculation formula:

Copper Number = (Vb - Vs) × N × 63.5 × 100 / W

Where:
Vb = volume of sodium thiosulphate used for blank (mL)
Vs = volume of sodium thiosulphate used for sample (mL)
N = normality of sodium thiosulphate
63.5 = atomic weight of copper (g/mol)
W = weight of fat or oil sample (g)

Example calculation:
Given: Vb = 20.0 mL, Vs = 15.0 mL, N = 0.1, W = 5.0 g

Step 1: Calculate volume difference
Vb - Vs = 20.0 mL - 15.0 mL = 5.0 mL

Step 2: Substitute values into formula
Copper Number = (5.0 × 0.1 × 63.5 × 100) / 5.0

Step 3: Arithmetic
= (31.75 × 100) / 5.0
= 3175 / 5.0
= 635 mg copper per 100 g of fat

The copper number of 635 indicates a high level of unsaturation. In practice, lower copper numbers are preferred in products requiring oxidative stability, such as leather conditioners. This calculation assists Kenyan industrial chemists in monitoring raw material quality and adjusting processing parameters accordingly.

Chapter Summary

This chapter covered essential analytical techniques used in the paper and allied industries, beginning with the calculation of the copper number, which measures the level of unsaturated compounds in fatty acids present in paper coatings. It then explored the determination of the kappa number, a critical parameter indicating the lignin content in pulp, which directly affects the bleaching process and final paper quality. The chapter also examined the viscosity test, highlighting its importance in assessing the degree of polymerization and strength properties of cellulose fibers. Finally, the starch test was discussed as a method to evaluate the presence and concentration of starch additives in paper products, which influence surface properties and printability. Each technique was presented with practical procedures for accurate measurement and interpretation of results. Together, these analyses provide a comprehensive understanding of paper composition and quality control, enabling optimization of manufacturing processes. Mastery of these tests supports consistent production of high-grade paper suitable for diverse industrial applications.