Methods for estimation of preservatives in treated timber and in treating solutions, Part 2: Determination of copper (in copper organic preservative salt) and pentachlorophenol
1991 Edition

Overview of Scope

• Quantitative assessment of:
  • Copper in copper organic preservative salt solutions and treated wood.
  • Pentachlorophenol in pentachlorophenol oil solutions and treated timber.

Essential Formula for Pentachlorophenol Determination

[ D = (A - B) \times 5.327 ] Where:

• (A) = ((\text{ml of silver nitrate for sample}) - (\text{ml of ammonium thiocyanate for sample}) \times \text{ammonium thiocyanate factor})
• (B) = ((\text{ml of silver nitrate for blank}) - (\text{ml of ammonium thiocyanate for blank}) \times \text{ammonium thiocyanate factor})
• (D) = Volume of sample in cubic centimeters

Additional Notes

• The standard facilitates quality control under BIS supervision.
• Results should be rounded following IS 2:1960 guidelines.
• Applicable to timber treated with copper organic salts and pentachlorophenol oils.

Summary Table

This specification complements IS 401:1982 relating to timber preservation.

Reagents Quality Standards

• Utilize high-purity chemicals and distilled water compliant with IS 1070:1977 to ensure analytical accuracy.

Copper Estimation Preparation

• Evaporate filtered preservative solution to eliminate organic material.
• Digest residue with 2 ml sulfuric acid and 3 ml nitric acid until fully dissolved.
• Heat until sulfur trioxide fumes develop, then cool and dilute.
• Neutralize with ammonium hydroxide to precipitate copper compounds.
• Redissolve precipitate with sulfuric acid, boil down, and dilute to final volume.
• Add 10 ml of 20% potassium iodide and 5 ml of 20% sodium thiocyanate.
• Titrate with sodium thiosulphate using starch as an indicator.

Pentachlorophenol Estimation Formula

[ \text{Kilograms of pentachlorophenol per cubic meter} = \frac{(A - B) \times 5.327}{D} ] Where symbols correspond as previously defined.

Preparation of 20% Potassium Iodide Solution

• Dissolve 20 grams of KI in water and dilute to 100 ml.

Diagram:

flowchart TD
    A[Filtered Treating Solution] --> B[Evaporate Solvent]
    B --> C[Add Acids and Heat]
    C --> D[Heat to Release SO3]
    D --> E[Neutralize and Prepare for Titration]

Overview

The standard defines chemical methods for measuring the copper content in copper organic preservative salts and wood treated with these preservatives.

Key Aspects

• Scope: Targets copper quantification in copper organic preservative salt solutions and treated timber.
• Reagents: Employ pure chemicals and distilled water per IS 1070:1977.
• Methodology: Extract copper from samples and determine concentration through complexometric titration (using EDTA) or colorimetric techniques.

Calculation Formula for Copper via EDTA Titration

[ \text{Copper concentration (mg/L)} = \frac{V \times N \times 63.5 \times 1000}{\text{Sample volume (mL)}} ] Where:

• (V) = Volume of EDTA used (mL)
• (N) = Normality of EDTA
• 63.5 = Atomic mass of copper

Summary Table

Diagram:

flowchart LR
    A[Sample Preparation] --> B[Copper Extraction]
    B --> C[EDTA Titration]
    C --> D[Copper Content Calculation]

Sample Preparation Details

• Ensure sample contains approximately 0.02 grams of copper to optimize titration accuracy.
• Evaporate filtered treating solution to dryness to remove organics.
• Digest with 2 ml sulfuric acid and 3 ml nitric acid, heating until dissolved.
• Heat further until sulfur trioxide fumes appear; cool and add water.
• Neutralize with ammonium hydroxide to precipitate copper compounds.
• Dissolve precipitate with sulfuric acid dropwise, boil down to 30 ml, cool below 20°C, and dilute to 125 ml.
• Add 10 ml of 20% potassium iodide and 5 ml of 20% sodium thiocyanate.
• Titrate with sodium thiosulphate using starch as an indicator near the endpoint.

Additional Procedures for Lime Nitrate Mixture

• Mix pentachlorophenol with lime nitrate in crucible; heat at 850-900°C for 20 minutes.
• Cool and extract residue with water and dilute nitric acid.
• Adjust volume and neutralize sample for titration.

Summary Table:

Essential Chemicals

• 20% Potassium Iodide Solution: Dissolve 20 grams KI in water and make up to 100 ml.
• 0.1 N Silver Nitrate Solution: Dissolve 16.989 grams AgNO₃ in water and dilute to 1 litre.
• Sodium Thiosulphate Solution: Prepare by dissolving 2.4821 grams Na₂S₂O₃·5H₂O in water to 1 litre.
• Ammonium Thiocyanate Solution: Prepared as specified in the relevant clause.

Summary Table:

Calculation Basis

• Estimations are conducted on a volume basis of timber to accommodate moisture content variability.

Scope

• Assessment of copper in copper organic preservative salt solutions and treated timber.
• Determination of pentachlorophenol in oil solutions and timber treated with it.

Formula Correction

• Use a factor of 0.0635 instead of 0.635 in specified calculations.

Typical Calculation for Pentachlorophenol Percentage

[ % \text{Pentachlorophenol} = \frac{C \times V \times F}{W} \times 100 ] Where:

• (C) = concentration from titration (mg/ml)
• (V) = volume of test solution (ml)
• (F) = dilution factor
• (W) = weight or volume of timber sample

Analytical Steps

1. Extract preservative from timber sample.
2. Perform chemical analysis to determine concentration.
3. Calculate preservative percentage using above formula.

Summary Table:

Diagram:

flowchart LR
    A[Treated Timber Sample] --> B[Extract Preservative]
    B --> C[Chemical Analysis]
    C --> D[Calculate Concentration]
    D --> E[Apply Correction Factor]
    E --> F[Estimate Percentage Based on Volume]

Formula for Pentachlorophenol Content (% by mass)

[ \text{PCP %} = \frac{(A - B) \times 0.532}{C} ] Where:

• (A) = ((\text{ml AgNO}_3 \text{ for sample}) - (\text{ml NH}_4\text{SCN for sample}) \times \text{NH}_4\text{SCN factor})
• (B) = ((\text{ml AgNO}_3 \text{ for blank}) - (\text{ml NH}_4\text{SCN for blank}) \times \text{NH}_4\text{SCN factor})
• (C) = Sample mass in grams
• 0.532 = Conversion factor derived from molecular weight and stoichiometry

Notes

• Volumes of silver nitrate and ammonium thiocyanate are titration readings.
• The ammonium thiocyanate factor corrects for standardization.
• Accurate weighing of samples is critical for precise results.

Summary Table:

This procedure ensures precise determination of pentachlorophenol concentration in oil solutions and treated timber.

Scope

• Applies to quantifying copper in copper organic preservative salts and pentachlorophenol in treated timber and treatment solutions.
• Supports adherence to IS 401:1982 timber preservation code.
• Ensures compliance with BIS quality inspection and control.

Sample Volume Calculation

[ D = (A - B) \times 5.327 ] Where:

• (A) = ((\text{ml silver nitrate for sample}) - (\text{ml ammonium thiocyanate for sample}) \times \text{ammonium thiocyanate factor})
• (B) = ((\text{ml silver nitrate for blank}) - (\text{ml ammonium thiocyanate for blank}) \times \text{ammonium thiocyanate factor})
• (D) = Sample volume in cubic centimeters
• Factor 5.327 converts volume basis to kilograms of pentachlorophenol per cubic meter of wood.

Sample Dimensions

• Increment boring size: 2 cm length, 0.475 cm diameter
• Calculated volume: approximately 0.3546 cm³

Titration Highlights

• Add 15 ml of 0.1 N silver nitrate and boil to coagulate silver chloride.
• Filter and wash until ammonium thiocyanate washes produce no turbidity.
• Final volume after washing is 200-250 ml.
• Back titrate excess silver nitrate with ammonium thiocyanate indicator.

Summary Table:

Preparation of Key Reagents

• 20% Potassium Iodide Solution: Dissolve 20 grams KI in water and make up to 100 ml.
• 0.1 N Standard Silver Nitrate Solution: Dissolve 16.989 grams silver nitrate in water and dilute to 1 litre.
• Ferric Ammonium Sulphate Indicator: Dissolve 10 grams ferric ammonium sulphate in 10 ml concentrated nitric acid, then dilute to 100 ml with distilled water.

Treating Solution Preparation Steps

1. Evaporate measured filtered solution until organic material is destroyed.
2. Add 2 ml sulfuric acid and 3 ml nitric acid, gently heat until dissolved.
3. Transfer to a 300 ml flask, heat until sulfur trioxide fumes appear and solution clears.
4. Wash flask walls with water, boil, cool, and neutralize with ammonium hydroxide until precipitate forms.
5. Add sulfuric acid dropwise until precipitate dissolves.
6. Boil down to 30 ml, cool below 20°C, then dilute to 125 ml.
7. Add 10 ml 20% potassium iodide and 5 ml 20% sodium thiocyanate; mix thoroughly.
8. Titrate with sodium thiosulphate, adding 2 ml starch indicator near endpoint; endpoint indicated by disappearance of blue color.

Summary Table:

Calculation Principles

• Estimation uses volume basis of timber to reduce errors from moisture variation.

Scope

• Quantitative determination of copper in copper organic preservative salts and treated timber.
• Pentachlorophenol quantification in oil-based preservatives and treated wood.

Correction Factor

• Apply 0.0635 instead of 0.635 in calculations as per specified clause.

Typical Calculation for Pentachlorophenol Percentage

[ % PCP = \frac{C \times V \times F}{W} \times 100 ] Where:

• (C): Concentration of pentachlorophenol in test solution (mg/ml)
• (V): Volume of test solution (ml)
• (F): Dilution factor
• (W): Weight or volume of timber sample

Procedure Overview

1. Extract preservative from timber.
2. Analyze concentration via titration or chemical methods.
3. Calculate preservative percentage on volume basis.

Diagram:

flowchart LR
    A[Treated Timber Sample] --> B[Extract Preservative]
    B --> C[Chemical Analysis]
    C --> D[Calculate Percentage]
    D --> E[Report Results]

Pentachlorophenol Content (% by Mass)

[ \text{PCP %} = (A - B) \times 0.5327 \times C ] Where:

• (A) = ((\text{ml silver nitrate for sample}) - (\text{ml ammonium thiocyanate for sample}) \times \text{ammonium thiocyanate factor})
• (B) = ((\text{ml silver nitrate for blank}) - (\text{ml ammonium thiocyanate for blank}) \times \text{ammonium thiocyanate factor})
• (C) = Sample mass in grams

Pentachlorophenol Content (kg/m³ of Wood)

[ \text{Content (kg/m}^3) = \frac{(A - B) \times 5.327}{D} ] Where (D) is sample volume in cm³.

Copper Content (kg/m³ of Wood)

[ \text{Copper (kg/m}^3) = \frac{M \times V \times 0.635}{M_1 \times 100} ] Where:

• (V) = volume of sodium thiosulphate used (ml)
• (M) = mass of sample (g)
• (M_1) = mass of one cubic meter of wood (kg)

Notes

• Calculations are based on volume to accommodate moisture content variability.
• Accurate titration volumes and sample measurements are essential.

Diagram:

flowchart TD
    A[Sample Preparation] --> B[Titration with Silver Nitrate]
    B --> C[Subtract Blank Values]
    C --> D[Calculate (A - B)]
    D --> E{Select Calculation}
    E -->|Pentachlorophenol %| F[Multiply by 0.5327 and Sample Mass]
    E -->|Pentachlorophenol kg/m³| G[Multiply by 5.327 and Divide by Sample Volume]
    E -->|Copper kg/m³| H[Apply Copper Formula]

Pentachlorophenol Content Reporting Formula

[ \text{PCP (kg/m}^3) = \frac{(A - B) \times 5.327}{D} ] Where symbols are as previously defined.

Reporting Instructions

• Final results should be rounded according to IS 2:1960 "Rules for rounding off numerical values".
• Clearly indicate units (e.g., kg/m³ for pentachlorophenol).
• Provide raw titration data along with calculated preservative concentrations.
• Include sample volume and reagent details for transparency.

Additional Information

• BIS Standard Mark ensures conformity under BIS quality control.
• Follow prescribed formulas and sample preparation steps for accurate reporting.

Diagram:

flowchart TD
    A[Sample Preparation] --> B[Titration]
    B --> C[Calculate A and B]
    C --> D[Apply Formula (A-B)*5.327/D]
    D --> E[Report PCP Content]
    E --> F[Round Off as per IS 2:1960]

Handling of Hazardous Chemicals

• Concentrated nitric acid and sulfuric acid must be handled within a fume hood due to their corrosive nature and toxic fumes.
• Personal protective equipment including gloves, goggles, and lab coats are mandatory.
• Ensure adequate ventilation and avoid direct exposure to vapors and skin contact.

Sample Treatment Safety

• Conduct evaporation and digestion steps cautiously under controlled conditions.
• Neutralize acidic solutions carefully with ammonium hydroxide to prevent vigorous reactions.
• Use starch indicator during titration to identify endpoint safely.

Important Formula

[ D = (A - B) \times 5.327 ] Where:

• (A) and (B) are defined as before.
• (D) represents volume basis pentachlorophenol content.

Safety Summary Table

Related Standards

• IS 401:1982 – Code of Practice for Timber Preservation (3rd Revision) outlines preservative types and treatment methods.
• IS 2753 Part 2 provides detailed methods for determining copper and pentachlorophenol in treated timber and solutions.

Key Formula Recap

[ D = (A - B) \times 5.327 ] where symbols are as previously described.

Standards Governance

• The BIS Act 1986 governs the use of the Standard Mark, ensuring products comply with quality through testing and inspection.
• Products bearing the Standard Mark comply with BIS quality control.

Updates and Amendments

• Indian Standards are periodically reviewed; users must verify they possess the latest version.

Rounding Off

• Follow IS 2:1960 for rounding numerical results.

BIS Office Contacts