Source: https://guthlabs.ai/docs/instruments/osmolarity-osmolality-calculator/mechanism/

instrument mechanism / verified-clean

# Osmolarity / Osmolality Calculator mechanism

The inspectable method record for Osmolarity / Osmolality Calculator, kept separate from implementation and qualification.

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

## Model scope

The educational-only label is appropriate and should remain prominent, especially because calculated osmolarity may differ from measured or clinically relevant osmolality. The UI must explicitly distinguish osmolarity (mOsm/L) from osmolality (mOsm/kg) and require or display concentration units.

- The formula Osm=Σ(Cᵢ·nᵢ) is standard for ideal osmolarity when Cᵢ is the molar concentration of each solute and nᵢ is its effective number of dissolved particles, but the spec does not state whether nᵢ assumes complete dissociation or incorporates an experimentally determined osmotic coefficient.

- The stated output unit is mOsm/L, but the formula does not specify the required conversion when concentrations are supplied in mol/L rather than mmol/L.

- The name includes osmolality, but the formula computes osmolarity only; osmolality requires concentration in osmoles per kilogram of solvent, typically reported as mOsm/kg.

## Units and conventions

- For the vectors below, concentrations explicitly labeled mmol/L are numerically multiplied by dimensionless particle counts to produce mOsm/L.

- If Cᵢ is supplied in mol/L, calculate Osm in mol/L and multiply the result by 1000 to obtain mOsm/L.

- nᵢ is dimensionless and represents the effective number of osmotically active particles per formula unit; values assume ideal behavior and complete dissociation unless otherwise specified.

- Osmolarity is expressed per liter of total solution, not per kilogram of solvent.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "solutes": [
      {
        "name": "glucose",
        "concentration": 5,
        "concentration_unit": "mmol/L",
        "particle_count": 1
      }
    ]
  },
  "expected_outputs": {
    "total_osmolarity_mOsm_per_L": 5
  },
  "working": "Osm = (5 mmol/L × 1) = 5 mOsm/L."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

An extreme but representable JavaScript input produces Infinity instead of a finite result, and the unspecified concentration unit permits a 1000-fold output discrepancy.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/osmolarity-osmolality-calculator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/osmolarity-osmolality-calculator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/osmolarity-osmolality-calculator/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`

- `BOUNDARY_HAZARD_CATALOG.json`