Methods of test for soils, Part 23: Determination of calcium carbonate

IS 2720 Part 23 - Scope Summary

• Title: Determination of Calcium Carbonate (CaCO₃) content in soils.
• Purpose: Establishes uniform procedures for CaCO₃ content testing affecting soil engineering properties.
• Application: Civil engineering soils testing.
• Method revision:
  • Originally used acetic acid; replaced by hydrochloric acid (HCl) for cost-effectiveness.
  • Simplified calculation by omitting factor 0.074 and blank titration.
• Significance: CaCO₃ content influences soil behavior and engineering performance.

Key Formula for CaCO₃ Percentage Calculation

[ \text{Percentage of CaCO}_3 = \frac{\text{Volume of HCl consumed (ml)} \times 0.05 \times 100}{\text{Weight of soil sample (g)}} ]

• Where:
  • 0.05 = Normality of HCl
  • Volume of HCl consumed = Titration volume for 5 g soil

Notes

• Test accuracy is sufficient for engineering interpretation.
• Results rounding per IS:2-1960.
• Part of IS 2720 series for soil testing methods.

flowchart TD
    A[Soil Sample (5g)] --> B[React with HCl]
    B --> C[Titrate HCl consumed]
    C --> D[Calculate % CaCO3 using formula]
    D --> E[Report CaCO3 content]

This scope defines the standardized approach to quantify calcium carbonate in soils for engineering decisions.

IS 2720 Part 23: Reagents and Indicators Summary

Key Reagents & Indicators:

• Hydrochloric Acid (HCl) Solution: Used to react with soil sample.
• Sodium Hydroxide (NaOH) Solution: Used for titration.
• Bromothymol Blue Indicator (Clause 3.3): Added during titration to detect endpoint.

Procedure Highlights (Clause 4.1):

• Weigh 5 g soil (adjust based on reaction intensity; see Note 1).
• Add 100 ml HCl solution to soil in 150-ml beaker.
• Stir vigorously for 1 hour, then pipette 20 ml supernatant.
• Add 6-8 drops bromothymol blue indicator.
• Titrate with NaOH solution until endpoint (color change).
• If color fades near endpoint, add more indicator.

Notes on Soil Weight (Note 1):

Important Specifications:

• Use Whatman No. 40 Filter Paper, 12.5 cm diameter (Clause 2.4).
• Accurate weighing and standardization of HCl and NaOH solutions are critical (Note 2).
• Periodically check solution strengths (Note 3).

Simplified Titration Flow:

flowchart TD
    A[Weigh Soil Sample] --> B[Add 100 ml HCl]
    B --> C[Stir 1 hour]
    C --> D[Pipette 20 ml supernatant]
    D --> E[Add Bromothymol Blue]
    E --> F[Titrate with NaOH]
    F --> G[Observe color change (endpoint)]

This method omits blank titration and factor 0.074 for simplicity and cost-effectiveness, maintaining sufficient accuracy for soil engineering properties.

IS 2720 Part 23 (1976) — Apparatus Specifications

• Burette: 50 ml capacity, conforming to IS:1997-1967.
• Filter Paper: Whatman No. 40 or equivalent, diameter 12.5 cm.
• Reagents: Hydrochloric acid (replaced acetic acid for cost efficiency).
• Calculation for CaCO3 content:

[ \text{Percentage of CaCO}_3 = \frac{\text{Volume of HCl consumed (ml)} \times 0.05 \times 100}{\text{Weight of soil sample (g)}} ]

For example, if 13.95 ml HCl is consumed by 5 g soil:

[ % \text{CaCO}_3 = \frac{13.95 \times 0.05 \times 100}{5} = 13.95% ]

• Rounding Off: Follow IS:2-1960 rules for numerical rounding.

Summary Table

flowchart LR
    SoilSample[Soil Sample (5g)]
    HCl[HCl Titration]
    VolumeHCl[Volume of HCl consumed (ml)]
    Calculation[Calculate % CaCO3]
    Result[Report % CaCO3]

    SoilSample --> HCl --> VolumeHCl --> Calculation --> Result

This apparatus and formula ensure accurate determination of calcium carbonate content in soils as per IS 2720 Part 23.

IS 2720 Part 23 (1976) — Sampling and Sample Preparation: Key Points

Sampling

• No explicit detailed procedure in provided context; follow general IS 2720 Part 1 for soil sample preparation.
• Use representative samples to avoid bias.
• Prepare samples by air drying and sieving as per test requirements.

Sample Preparation

• Use Whatman No. 40 filter paper (12.5 cm diameter) for filtration.
• Replace acetic acid with hydrochloric acid (HCl) in chemical tests for cost-effectiveness.
• Blank titration omitted to save time with negligible accuracy loss.

Key Formula for Calcium Carbonate (CaCO₃) Content:

[ % \text{CaCO}_3 = \frac{13.95 \times V \times 100}{W} ]

Where:

• ( V ) = Volume of HCl consumed (in ml)
• ( W ) = Weight of soil sample (in grams, typically 5 g)

Notes:

• Factor 0.074 (original method) omitted due to insignificant effect.
• Results rounding as per IS 2-1960 rules.

Summary Table: Reagents & Materials

flowchart TD
    A[Soil Sampling] --> B[Air Drying]
    B --> C[Sieving]
    C --> D[Chemical Test Preparation]
    D --> E[Add HCl]
    E --> F[Titration]
    F --> G[Calculate %CaCO3]

For detailed procedures, refer to IS 2720 Part 1 and Part 23 full text.

IS 2720 Part 23 (1976) — Test Procedure for Determination of Calcium Carbonate in Soils

Key Points & Formula:

• Acid Used: Hydrochloric acid (HCl) replaces acetic acid for titration.
• Sample: 5 g of soil is used for titration.
• Calculation of CaCO₃ percentage:

[ \text{Percentage of CaCO}_3 = \frac{\text{Volume of HCl consumed (ml)} \times \text{Normality of HCl} \times 100}{\text{Weight of soil sample (g)}} ]

• From Clause 13.95 example,

[ % \text{CaCO}_3 = \frac{13.95 \times 0.05 \times 100}{5} = 13.95% ]

where:

• 13.95 ml = volume of HCl consumed,
• 0.05 N = normality of HCl,
• 5 g = soil sample weight.

Specifications:

• Blank titration omitted for time saving.
• Factor 0.074 from original method omitted due to insignificance.
• Final results rounded as per IS:2-1960.

Summary Table:

flowchart TD
    A[Soil Sample (5g)] --> B[Titration with 0.05N HCl]
    B --> C[Measure Volume of HCl consumed (V ml)]
    C --> D[Calculate % CaCO3 using formula]
    D --> E[Report Results (Rounded as per IS:2-1960)]

This method ensures accurate and economical determination of calcium carbonate content in soils for engineering interpretation.

IS 2720 Part 23 (1976) — Determination of Calcium Carbonate in Soils

Key Formula for CaCO₃ Content Calculation:

[ \text{Percentage of CaCO}_3 = \frac{13.95 \times V \times 100}{W} ]

• V = Volume of HCl consumed (in ml)
• W = Weight of soil sample (in g), typically 5 g

Example:
If 13.95 ml of HCl is consumed by 5 g soil,
[ % \text{CaCO}_3 = \frac{13.95 \times 13.95 \times 100}{5} = 13.95% ]

Notes:

• Hydrochloric acid (HCl) is used instead of acetic acid for titration.
• The factor 0.074 from the original method is omitted for simplicity.
• Blank titration is omitted to save time without significant loss of accuracy.
• Results should be rounded as per IS 2-1960 rules.

Summary Table:

flowchart TD
    A[Soil Sample (5g)] --> B[Titration with HCl]
    B --> C[Measure Volume of HCl (V ml)]
    C --> D[Calculate % CaCO3 using formula]
    D --> E[Report CaCO3 Content]

This method helps assess soil carbonate content affecting soil engineering properties.

IS 2720 Part 23 (1976) — Key Notes and Precautions for CaCO3 Determination

Important Points:

• Reagent: Hydrochloric acid (HCl) replaced acetic acid for cost-effectiveness.
• Calculation Simplification: The factor 0.074 from the original method is omitted due to negligible effect.
• Blank Titration: Omitted to save time without compromising accuracy.
• Filter Paper: Use Whatman No. 40 or equivalent, 12.5 cm diameter.
• Rounding Off: Follow IS 2-1960 rules for rounding numerical results.

Key Formula for % CaCO3:

[ \text{Percentage of CaCO}_3 = \frac{\text{Volume of HCl consumed (ml)} \times N \times 50}{\text{Weight of soil sample (g)}} ]

Where:

• (N) = Normality of HCl (usually 0.05 N)
• 50 = Equivalent weight factor of CaCO3 (g/eq)

Example: If 13.95 ml of 0.05 N HCl is consumed by 5 g soil, [ % \text{CaCO}_3 = \frac{13.95 \times 0.05 \times 50}{5} = 13.95% ]

Precautions:

• Use standardized HCl solution.
• Ensure complete reaction between soil and acid.
• Avoid contamination and moisture in samples.
• Follow IS guidelines strictly for sample preparation and titration.

flowchart TD
    A[Soil Sample (5g)] --> B[Add HCl (0.05 N)]
    B --> C[Reaction: CaCO3 + HCl]
    C --> D[Titrate remaining HCl with NaOH]
    D --> E[Calculate volume of HCl consumed]
    E --> F[Compute % CaCO3 using formula]

This method balances accuracy with efficiency for engineering soil analysis.

IS 2720 Part 23 (1976) - Accuracy and Standardization Key Points

• Standardization of Hydrochloric Acid (Clause 3.2):
  Prepare 1 N HCl by diluting 175 ml concentrated HCl to 2 L. Standardize against NaOH to find exact normality (factor).

• Accuracy:

  • Acetic acid replaced by HCl for cost efficiency.
  • Factor 0.074 omitted as insignificant.
  • Blank titration omitted to save time without compromising accuracy.
  • Accuracy is deemed sufficient for engineering soil property interpretation.

• Calculation of CaCO3 Content (Clause 13.95):
  [ % \text{CaCO}_3 = \frac{\text{Volume of HCl (ml)} \times \text{Normality of HCl} \times 100}{\text{Weight of soil sample (g)} \times 5} ]

  Example: For 5 g soil, if 13.95 ml of 1 N HCl consumed,
  [ % \text{CaCO}_3 = 13.95% ]

• Equipment:
  Use 50 ml burette as per IS:1997-1967 for titration.

• Rounding Off Results:
  Follow IS:2-1960 rules for numerical rounding.

Summary Table: Standardization and Calculation

flowchart TD
    A[Prepare 1N HCl] --> B[Standardize HCl with NaOH]
    B --> C[Titrate soil sample]
    C --> D[Calculate CaCO3 % using formula]
    D --> E[Report results with IS rounding rules

IS 2720 Part 23 (1976) - Reporting of Results for Calcium Carbonate Determination

Key Specifications:

• Rounding Off: Final values must be rounded as per IS 2-1960 rules.
• Reagents: Hydrochloric acid replaces acetic acid for titration.
• Filter Paper: Use Whatman No. 40 or equivalent, 12.5 cm diameter.
• Sample: 5 g soil used for titration.

Key Formula for % CaCO₃:

[ \text{Percentage of CaCO}_3 = \frac{13.95 \times V \times 100}{5} ]

Where:

• (V) = Volume of HCl consumed (in ml)
• 13.95 = Equivalent weight factor of CaCO₃ in HCl titration (unit conversion factor)
• 5 = Weight of soil sample in grams

Notes:

• Blank titration and factor 0.074 omitted for efficiency without affecting accuracy.
• Results interpretation aligns with engineering properties of soils.

Summary Table:

flowchart TD
    A[Soil Sample (5g)] --> B[Titration with HCl]
    B --> C[Volume of HCl consumed (V)]
    C --> D[Calculate % CaCO3]
    D --> E[Apply formula: (13.95 × V × 100) / 5]
    E --> F[Round off as per IS 2-1960]
    F --> G[Report final % CaCO3]

This ensures consistent, accurate reporting of calcium carbonate content in soils per IS 2720 Part 23.