Source: https://guthlabs.ai/docs/instruments/colligative-properties-suite/mechanism/

instrument mechanism / verified-clean

# Colligative Properties Suite mechanism

The inspectable method record for Colligative Properties Suite, kept separate from implementation and qualification.

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

## Model scope

Core colligative-property equations are recognizable and standard under ideal dilute-solution assumptions, but the specification is not complete enough for an unambiguous implementation. Exact ambiguities requiring review are: whether the vapor-pressure output means P_solution or ΔP; which pure-solvent boiling/freezing reference points are used for new temperatures; whether osmotic-pressure R uses L·atm or SI units; and how solvent selection maps to Kb, Kf, pure phase-transition points, and temperature-specific vapor-pressure data.

- ΔTb=i·Kb·m and ΔTf=i·Kf·m are standard dilute-solution formulas when m is solute molality in mol/kg solvent and Kb/Kf use matching K·kg·mol^-1 units.

- π=iMRT is the standard ideal dilute-solution formula, but it requires absolute temperature and a consistent molarity/R unit system; concentrated solutions require activities or an osmotic-coefficient correction.

- P_solution=x_solvent·P°_solvent is Raoult's-law solution vapor pressure, not vapor-pressure lowering. The lowering formula is ΔP=P°_solvent−P_solution=x_solute·P°_solvent for a binary ideal solution.

- The claimed new boiling and freezing points require additional formulas and pure-solvent reference values: Tb,new=Tb°+ΔTb and Tf,new=Tf°−ΔTf. These formulas and required baseline inputs are absent.

- The phrase 'Kb/Kf (or solvent selection)' is incomplete unless the solvent table supplies Kb, Kf, normal boiling/freezing points, and the temperature-dependent pure-solvent vapor pressure.

## Units and conventions

- m is molality in mol solute per kg solvent; Kb and Kf are in K·kg·mol^-1, numerically equivalent to °C·kg·mol^-1 for temperature differences.

- M is molarity in mol/L when R=0.082057 L·atm·mol^-1·K^-1, or M must be converted to mol/m^3 when using an SI R value.

- T in π=iMRT must be in kelvin, not °C.

- i is dimensionless and represents the effective van't Hoff factor under the stated solution conditions.

- x_solvent is the mole fraction of solvent, constrained to 0≤x_solvent≤1; P° and P_solution must use the same pressure units and the same temperature.

- Raoult's law assumes an ideal solution and uses the pure-solvent vapor pressure at the specified temperature.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "property": "boiling_point_elevation",
    "solvent": "water",
    "i": 2,
    "Kb": 0.512,
    "Kb_units": "K·kg·mol^-1",
    "m": 0.5,
    "m_units": "mol·kg^-1",
    "Tb_pure_C": 100
  },
  "expected_outputs": {
    "delta_Tb_K": 0.512,
    "new_boiling_point_C": 100.512
  },
  "working": "ΔTb=i·Kb·m=2.0×0.512×0.500=1.024×0.500=0.512 K. Tb,new=Tb°+ΔTb=100.000+0.512=100.512 °C."
}
````

## Failure boundary

- Division-by-zero and invalid-input hazards can arise in upstream calculations of molarity, molality, or mole fractions if solvent mass, solution volume, or total mole amount is zero.

- Reject negative molality, molarity, temperature, Kb, Kf, or pressure values; enforce 0≤x_solvent≤1.

- Using Celsius directly in π=iMRT produces an incorrect result; temperature must be converted to kelvin.

- Mixing molality and molarity, or using Kb/Kf with incompatible units, produces dimensionally incorrect temperature changes.

- The van't Hoff factor is not always an integer and may vary with concentration, dissociation, association, or ion pairing; treating it as exact requires an explicit approximation.

- The dilute ideal-solution formulas may be inaccurate for concentrated electrolytes or nonideal solutions.

- P°_solvent is strongly temperature-dependent; the solvent vapor-pressure table must identify the temperature and pressure units.

- The current vapor-pressure formula does not directly return the claimed vapor-pressure lowering.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/colligative-properties-suite/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/colligative-properties-suite/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/colligative-properties-suite/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-tranche4/tranche4-results.json`