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

instrument mechanism / verified-clean

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

The inspectable method record for Specific Heat Ratio (γ) / Cp,Cv Lookup, kept separate from implementation and qualification.

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

## Model scope

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.

- 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.

## Units and conventions

- 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.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "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."
}
````

## Failure boundary

**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.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/specific-heat-ratio-cp-cv-lookup/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/specific-heat-ratio-cp-cv-lookup/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/specific-heat-ratio-cp-cv-lookup/qualification/>)

## Sources and evidence

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

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`