Source: https://guthlabs.ai/docs/instruments/specific-heat-ratio-cp-cv-lookup/

instrument / verified-clean

# Specific Heat Ratio (γ) / Cp,Cv Lookup

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/specific-heat-ratio-cp-cv-lookup/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/specific-heat-ratio-cp-cv-lookup/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/specific-heat-ratio-cp-cv-lookup/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/specific-heat-ratio-cp-cv-lookup/qualification/>)

## Ledger state

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

**Area**: Thermodynamics, Fluids & Aero

**Tranche**: tranche-7

**Evidence ID**: t7-108

**Ledger rows**: 1

No ledger note is attached.

## Review findings

The core γ formula is sound, and the ideal-gas mass-basis R relation is sound under its stated assumptions. Verdict is NEEDS_REVIEW because the specification does not define the table edition, composition, basis, interpolation behavior, valid temperature range, or pressure/phase convention, and its R=Cp−Cv wording is too broad for real-gas thermodynamics.

### Formula and scope findings

- γ=Cp/Cv is correct when Cp and Cv use the same basis and units.

- R=Cp−Cv is correct for an ideal gas on a consistent mass basis, but is not generally valid for real gases or arbitrary tabulated thermodynamic states.

- The specification does not define whether lookup values are mass-based or molar-based; the stated R formula requires a consistent basis.

- The temperature-dependent option does not specify interpolation, extrapolation, pressure, phase, or reference-state conventions. Steam especially requires pressure/phase qualification.

- The claim of providing properties for common gases is under-specified because no actual table version, gas composition, or reference conditions are identified.

### Unit assumptions

- Test-vector Cp, Cv, and R values are mass-specific in J/(kg·K).

- Temperature values used for lookup are absolute kelvin unless an input explicitly carries a Celsius unit.

- γ is dimensionless.

- The tabulated values represent ideal-gas reference values; pressure dependence is ignored.

- For the interpolation vector, linear interpolation in temperature is assumed only between the explicitly supplied bracketing rows.

## Boundary hardening

**BREAK_CLAIMED** · SELF_FLAGGED

The specification does not define table-validity limits, a temperature-branch threshold, or the Cp/Cv unit basis. An implementation could accept 0 K or extreme temperatures, silently extrapolate, reuse reference values across a temperature branch, or report mass-specific values with molar units.

## 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": {
    "gas": "dry air",
    "temperature_K": 300
  },
  "expected_outputs": {
    "Cp_J_per_kg_K": 1005,
    "Cv_J_per_kg_K": 718,
    "gamma": 1.3997214485,
    "R_J_per_kg_K": 287
  },
  "reference_data": {
    "table_row": {
      "temperature_K": 300,
      "Cp_J_per_kg_K": 1005,
      "Cv_J_per_kg_K": 718,
      "R_J_per_kg_K": 287,
      "source_convention": "Widely tabulated standard ideal-dry-air value; textbook/CRC convention"
    }
  },
  "working": "γ = Cp/Cv = 1005/718 = 1.3997214485. R = Cp − Cv = 1005 − 718 = 287 J/(kg·K). The R = 287 J/(kg·K) dry-air value is the standard memorized reference value."
}
````

## 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-tranche7/tranche7-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`