Gran Titration Alkalinity

Fit the post-equivalence acid Gran function (Vs+Va)·10^(−pH) and extrapolate a nonnegative endpoint for monovalent acid alkalinity; activity corrections and endpoint validity require laboratory assessment.

Description

Gran titration estimates an acid-neutralization endpoint by extrapolating a linear transformed post-equivalence series.

Gran titration estimates an acid-neutralization endpoint by extrapolating a linear transformed post-equivalence series. The endpoint and acid strength then give alkalinity for the original sample.^[1]

The tool returns granEndpointVolumeMl, alkalinityMilliequivalentsPerLiter, granFitRSquared. The computation uses supplied observations and parameters rather than acquiring measurements.

When to use Gran Titration Alkalinity

Use this for the following task: Fit the post-equivalence acid Gran function (Vs+Va)·10^(−pH) and extrapolate a nonnegative endpoint for monovalent acid alkalinity; activity corrections and endpoint validity require laboratory assessment. Prepare observations and calibration parameters on the same unit and reporting basis.

How to use Gran Titration Alkalinity and understand its results

Prepare the measured quantities and supplied model parameters. Match the units and align paired lists before calculating.
Enter sampleVolumeMl, acidVolumesMl, measuredPhValues, acidConcentrationMolesPerLiter according to the field table, then run the tool.
Read granEndpointVolumeMl, alkalinityMilliequivalentsPerLiter, granFitRSquared. Use the calculation below to interpret the selected mean or the model’s signs, units and comparison flags.
Review the supplied assumptions and calibration before comparing or reporting the result.

Input field	Meaning	Value type and bounds	Requirement
sampleVolumeMl	Sample volume ml	number	Required
acidVolumesMl	Acid volumes ml	list of number	Required
measuredPhValues	Measured ph values	list of number	Required
acidConcentrationMolesPerLiter	Acid concentration moles per liter	number	Required

Supply positive sample volume and monovalent acid concentration, increasing nonnegative acid volumes and aligned pH observations. Fit the Gran function, require positive slope and an endpoint from zero through the first sampled acid volume.

Gran=(sampleVolume+acidVolume)×10^(−pH); endpoint=−intercept/slope; meq/L=1000×acidConcentration×endpoint/sampleVolume

The symbols and boundary conditions refer to the supplied fields and the implementation described above.

Output field	Meaning	Value type
granEndpointVolumeMl	Gran endpoint volume ml	number
alkalinityMilliequivalentsPerLiter	Alkalinity milliequivalents per liter	number
granFitRSquared	Gran fit r squared	number

json

{
  "input": {
    "sampleVolumeMl": 10,
    "acidVolumesMl": [
      2,
      3,
      4
    ],
    "measuredPhValues": [
      3.0791812460476247,
      2.8129133566428557,
      2.6690067809585756
    ],
    "acidConcentrationMolesPerLiter": 0.1
  },
  "output": {
    "granEndpointVolumeMl": 0.9999999999999997,
    "alkalinityMilliequivalentsPerLiter": 9.999999999999996,
    "granFitRSquared": 1
  }
}

Limitations and assumptions

Choose post-equivalence observations and assess activity effects externally. Fit quality does not establish a chemically appropriate endpoint, and polyvalent acid conventions are not inferred.

Numerical inputs must be finite. Input-shape and calculation checks do not establish measurement quality or the validity of a supplied calibration.

Alternative or Complementary methods

Choose Chlorophyll A Extraction Concentration when you need its operation: Convert blank-corrected multiwavelength extract absorbances with caller method coefficients and path/dilution/sample-volume correction; negative estimates are retained and solvent-specific calibration is external. Choose Nitrogen Phosphorus Ratio Limitation Checker for the complementary operation: Convert matched mass N/P concentrations to molar ratio and screen caller bounds; ratios alone cannot diagnose nutrient limitation or bioavailability.

Background reference: Methods for Alkalinity Calculator: Gran titration.

References

Methods for Alkalinity Calculator: Gran titration — U.S. Geological Survey

Similar or alternative tools

Chlorophyll A Extraction Concentration
Convert blank-corrected multiwavelength extract absorbances with caller method coefficients and path/dilution/sample-volume correction; negative estimates are retained and solvent-specific calibration is external.
Nitrogen Phosphorus Ratio Limitation Checker
Convert matched mass N/P concentrations to molar ratio and screen caller bounds; ratios alone cannot diagnose nutrient limitation or bioavailability.