Source: https://guthlabs.ai/docs/instruments/seawater-density-simplified-eos/implementation/

instrument implementation / implementation-contract

# Seawater Density (simplified EOS) implementation

A source-bound implementation contract for Seawater Density (simplified EOS); deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t7-110

**Effect**: Computation or source lookup only

## Input and validation requirements

The negative-salinity vector produces an undefined real result and must be rejected. The convention probe also exposes a unit-label hazard: interpreting an unlabeled temperature value of 10 as Celsius versus Fahrenheit changes the expected density substantially.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "temperature_C": 0,
    "salinity_PSU": 0,
    "pressure_dbar": 0
  },
  "expected_outputs": {
    "density_kg_m3": 999.842594
  },
  "reference_data": {
    "rho_w_coefficients": {
      "a0": 999.842594,
      "a1": 0.06793952,
      "a2": -0.00909529,
      "a3": 0.0001001685,
      "a4": -0.000001120083,
      "a5": 6.536332e-9
    },
    "source_convention": "Widely tabulated standard value, UNESCO EOS-80/UNESCO Technical Papers in Marine Science 44 atmospheric pure-water density polynomial"
  },
  "working": "Use rho_w(T)=a0+a1*T+a2*T^2+a3*T^3+a4*T^4+a5*T^5. At T=0: rho_w=999.842594+0.06793952*0-0.00909529*0^2+0.0001001685*0^3-0.000001120083*0^4+0.000000006536332*0^5=999.842594 kg/m^3. At S=0, all salinity terms are zero, so rho=999.842594 kg/m^3."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/seawater-density-simplified-eos/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/seawater-density-simplified-eos/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/seawater-density-simplified-eos/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`