Source: https://guthlabs.ai/docs/instruments/percent-solution-concentration-unit-converter-865c2ba7/mechanism/

instrument mechanism / verified-clean

# Percent Solution / Concentration Unit Converter mechanism

The inspectable method record for Percent Solution / Concentration Unit Converter, kept separate from implementation and qualification.

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

## Model scope

The listed instrument behavior is not fully verifiable because the spec lacks explicit formulas and does not define the basis of ppm or the density convention. The exact ambiguities requiring resolution are: ppm basis (w/w, v/v, or mg/L), which density applies in each mass-volume conversion, required units and validation for MW/density, and the direction-specific formulas for every supported unit pair.

- The formula specification is not explicit: "cross-unit conversions via density/MW where applicable" does not define the direction-specific equations or the exact density relationships.

- ppm is ambiguous because it may mean ppm by mass (mg/kg), ppm by volume (µL/L), or, in aqueous contexts, mg/L. The target unit must specify its basis.

- %w/v to mg/mL has the standard relation 1% w/v = 1 g/100 mL = 10 mg/mL.

- %v/v to ppm is only directly convertible when ppm is explicitly ppm v/v: x% v/v = 10,000x ppm v/v.

- Molarity to mg/mL uses mg/mL = mol/L × molecular weight in g/mol; the MW input must be for the exact chemical species and formula state.

- Conversions involving %v/v and mass-based units require a clearly defined density, generally solution density for mass concentration of solution and/or pure-solute density for solute volume. The required density is not specified.

## Units and conventions

- %w/v means grams of solute per 100 mL of final solution.

- %v/v means milliliters of solute per 100 mL of final solution.

- Molarity means moles of solute per liter of final solution.

- For the molarity test, MW is in g/mol and the exact compound has MW 58.44 g/mol.

- For the %v/v-to-ppm test, ppm is interpreted as ppm v/v, meaning volume fraction × 1,000,000.

- For the mg/mL-to-ppm test, ppm is interpreted as aqueous-equivalent mg/L, using solution density 1.000 kg/L; this is not generally valid for nonaqueous or concentrated solutions.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "value": 1,
    "source_unit": "%w/v",
    "target_unit": "mg/mL"
  },
  "expected_outputs": {
    "value": 10,
    "unit": "mg/mL"
  },
  "working": "1% w/v = 1 g per 100 mL. 1 g = 1000 mg, so 1 g/100 mL = 1000 mg/100 mL = 10 mg/mL."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

A zero density creates a genuine division-by-zero case that must be rejected. The ppm test also exposes a convention hazard: aqueous ppm and mass-based ppm produce different results when density is not 1.0.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/percent-solution-concentration-unit-converter-865c2ba7/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/percent-solution-concentration-unit-converter-865c2ba7/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/percent-solution-concentration-unit-converter-865c2ba7/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-tranche5/tranche5-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`