Source: https://guthlabs.ai/docs/instruments/ph-henderson-hasselbalch-calculator/

instrument / verified-clean

# pH / Henderson-Hasselbalch Calculator

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Inspectable records

[01**Overview**Purpose and lifecycle](<https://guthlabs.ai/docs/instruments/ph-henderson-hasselbalch-calculator/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/ph-henderson-hasselbalch-calculator/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/ph-henderson-hasselbalch-calculator/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/ph-henderson-hasselbalch-calculator/qualification/>)

## Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

**Area**: Biology, Medicine & Pharmacology (educational estimates only — every panel labeled not-medical-advice)

**Tranche**: tranche-4

**Evidence ID**: t4-158

**Ledger rows**: 1

No ledger note is attached.

## Review findings

The chemistry formula is valid under its stated assumptions, and the existing educational/not-medical-advice label is appropriate. Review is required to define the buffer-capacity note and to specify whether blood calculations accept dissolved CO2 concentration or PCO2, including the required units and coefficient.

### Formula and scope findings

- pH=pKa+log10([A-]/[HA]) is the standard Henderson-Hasselbalch equation for a conjugate acid-base pair, provided the ratio is dimensionless and concentrations are positive.

- The claimed 'buffer capacity note' has no definition or formula, so that output cannot be verified or reproducibly generated.

- The phrase 'acid-base blood parameter estimate' is ambiguous: clinical bicarbonate systems commonly use pH=6.1+log10([HCO3-]/(0.03×PCO2)) when PCO2 is supplied in mmHg, whereas the stated concentration-ratio formula requires dissolved CO2 concentration as [HA].

### Unit assumptions

- log means base-10 logarithm.

- [A-] and [HA] must be expressed in the same concentration units, or converted before division; their ratio is dimensionless.

- pKa is dimensionless and must correspond to the specified acid-base pair and relevant temperature, ionic strength, and chemical conditions.

- For bicarbonate blood calculations using PCO2 rather than dissolved CO2 concentration, the applicable coefficient and PCO2 units must be explicitly specified.

## Boundary hardening

**BREAK_CLAIMED** · SELF_FLAGGED

A zero conjugate-acid concentration causes division by zero, making the pH undefined; the instrument must reject the input rather than force a numeric result. There is also a convention hazard if the ratio direction or logarithm base is not made explicit.

## Errata and corrections

No applied erratum is attached to this unique-name record.

## Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

````
{
  "inputs": {
    "pKa": 4.76,
    "conjugate_base": "0.100 mol/L acetate",
    "conjugate_acid": "0.100 mol/L acetic acid"
  },
  "expected_outputs": {
    "pH": 4.76
  },
  "working": "A-/HA = 0.100 mol/L ÷ 0.100 mol/L = 1. pH = 4.76 + log10(1) = 4.76 + 0 = 4.76."
}
````

## Related workflows

No source-defined multi-instrument workflow membership is recorded.

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`

- `evidence-tranche4/tranche4-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`