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

instrument / verified-clean

# Percent Solution / Concentration-Unit Converter

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/percent-solution-concentration-unit-converter/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/percent-solution-concentration-unit-converter/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/percent-solution-concentration-unit-converter/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/percent-solution-concentration-unit-converter/qualification/>)

## Ledger state

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

**Area**: Chemistry & Materials

**Tranche**: tranche-3

**Evidence ID**: t3-015

**Ledger rows**: 1

No ledger note is attached.

## Review findings

The specification needs explicit formulas and required inputs for every conversion path, especially %w/w↔%w/v↔%v/v, ppm/ppb, molarity↔molality, and mole fraction. The honest label should state that ppm↔molarity also requires solute molar mass and that density supplied alone does not resolve the distinction between mass-based and volume-based ppm conventions.

### Formula and scope findings

- The %w/v formula is correct only when solute mass is in grams and solution volume is in milliliters: (g/100 mL)×100 simplifies to g solute per 100 mL solution.

- ppm=mg/L is not a universal ppm definition; it is a dilute aqueous mass/volume approximation. ppm may instead mean mg/kg by mass, and the approximation requires an explicit density assumption.

- The molarity↔molality relationship is not specified. With density rho in g/mL, solute molar mass MW in g/mol, molarity C in mol/L, and molality b in mol/kg, the formulas are b=(1000C)/(1000rho−C×MW) and C=(1000rho×b)/(1000+b×MW).

- Conversions among %w/w, %w/v, and %v/v require additional quantities that are not listed, including solution density and, for %v/v conversions involving solute mass, solute density.

- Mole-fraction conversion requires the solvent identity or solvent molar mass and the relevant solute/solvent amounts; solute molar mass alone is insufficient.

- An atomic weights table is insufficient for arbitrary solute molar mass unless a molecular formula and a molecular-weight calculation are also supported.

### Unit assumptions

- %w/v uses grams of solute and milliliters of final solution.

- Molarity is mol solute per liter of final solution.

- Molality is mol solute per kilogram of solvent, not per kilogram of solution.

- The molarity↔molality formulas assume solution density is in g/mL and solute molar mass is in g/mol.

- The ppm and ppb test conversions use the dilute aqueous approximation: 1 ppm=1 mg/L and 1 ppb=1 microgram/L.

- For mole fraction in the applicable test vector, the solvent is water with molar mass 18.015 g/mol.

## Boundary hardening

**BREAK_CLAIMED** · SELF_FLAGGED

The specification exposes two concrete failure hazards: 100% w/w causes division by zero in molality, and several requested conversions, especially %v/v, are underdetermined without solute density. ppm-to-molarity also changes from an approximate dilute-aqueous branch to a density-corrected branch when density is supplied.

## 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": {
    "solute_mass_g": 5,
    "solution_volume_mL": 100,
    "solute_molar_mass_g_per_mol": 58.44,
    "medium": "dilute aqueous"
  },
  "expected_outputs": {
    "percent_w_v": 5,
    "solute_mass_g_per_L": 50,
    "molarity_mol_per_L": 0.855578
  },
  "working": "%w/v=(5 g/100 mL)×100=5% w/v. 100 mL=0.100 L, so 5 g/0.100 L=50 g/L. Molarity=50 g/L ÷ 58.44 g/mol=0.855578 mol/L. Under the dilute-aqueous assumption, ppm=50 g/L×1000 mg/g=50000 mg/L=50000 ppm."
}
````

## 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-tranche3/tranche3-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`