{
  "version": 1,
  "topic": "PV05",
  "title": "Gas gravity API gravity and specific gravity",
  "createdAt": "2026-10-24",
  "case": {
    "title": "API Gravity",
    "premise": "Fixed controls: . SG_o is varied as shown.",
    "formula": "API = \\frac{141.5}{SG_o} - 131.5",
    "variables": "SG_o: Specific Gravity of Oil Phase (dimensionless).",
    "steps": [
      {
        "label": "Define the baseline",
        "calculation": "Specific Gravity of Oil Phase (dimensionless) = 0.85",
        "explanation": "Fixed controls: . SG_o is varied as shown."
      },
      {
        "label": "Select the relation",
        "calculation": "API = \\frac{141.5}{SG_o} - 131.5",
        "explanation": "SG_o: Specific Gravity of Oil Phase (dimensionless)."
      },
      {
        "label": "Substitute the values",
        "calculation": "SG_o = 0.85 → API = 34.9705882 dimensionless",
        "explanation": "Retain intermediate precision. The displayed values are rounded only after evaluation."
      },
      {
        "label": "Read the result",
        "calculation": "API (dimensionless) = 34.9705882",
        "explanation": "Higher liquid specific gravity corresponds to lower API on the specified reference basis."
      }
    ],
    "result": "API (dimensionless) = 34.9705882",
    "interpretation": "Higher liquid specific gravity corresponds to lower API on the specified reference basis.",
    "control": "Specific Gravity of Oil Phase (dimensionless)",
    "columns": [
      "Specific Gravity of Oil Phase (dimensionless)",
      "API (dimensionless)"
    ],
    "rows": [
      [
        0.7,
        70.64285714285717
      ],
      [
        0.8,
        45.375
      ],
      [
        0.85,
        34.970588235294116
      ],
      [
        0.9,
        25.72222222222223
      ],
      [
        1,
        10
      ]
    ],
    "baseline": 2,
    "rowNotes": [
      "Specific Gravity of Oil Phase (dimensionless) = 0.7. API (dimensionless): 70.6428571.",
      "Specific Gravity of Oil Phase (dimensionless) = 0.8. API (dimensionless): 45.375.",
      "Specific Gravity of Oil Phase (dimensionless) = 0.85. API (dimensionless): 34.9705882.",
      "Specific Gravity of Oil Phase (dimensionless) = 0.9. API (dimensionless): 25.7222222.",
      "Specific Gravity of Oil Phase (dimensionless) = 1. API (dimensionless): 10."
    ],
    "provenance": "Replayed with the same equation record and calculation engine as /calculators/api-gravity. Original synthetic inputs; engine outputs are saved in the downloadable record.",
    "questions": [
      {
        "question": "Reproduce the baseline API (dimensionless) without rounding intermediate values.",
        "answer": "SG_o = 0.85 → API = 34.9705882 dimensionless. API (dimensionless) = 34.9705882. Higher liquid specific gravity corresponds to lower API on the specified reference basis."
      },
      {
        "question": "Compare the first and last recorded scenarios. Which input changes?",
        "answer": "Specific Gravity of Oil Phase (dimensionless) changes from 0.7 to 1. Other controls remain as stated in the premise. API (dimensionless) changes from 70.6428571 to 10."
      },
      {
        "question": "What would be needed to apply this example to a different physical system?",
        "answer": "Replace the synthetic controls with compatible documented inputs and check the relation's assumptions. SG_o: Specific Gravity of Oil Phase (dimensionless). Higher liquid specific gravity corresponds to lower API on the specified reference basis."
      }
    ]
  },
  "recorded": {
    "kind": "scalar",
    "equation": "api-gravity",
    "parameter": "SG_o",
    "inputs": {
      "SG_o": "0.85"
    },
    "values": [
      0.7,
      0.8,
      0.85,
      0.9,
      1
    ],
    "outputs": [
      {
        "expression": "141.5 / SG_o - 131.5",
        "intermediates": {},
        "inputs": {
          "SG_o": 0.7
        },
        "target": "API",
        "unit": "dimensionless",
        "value": 70.64285714285717
      },
      {
        "expression": "141.5 / SG_o - 131.5",
        "intermediates": {},
        "inputs": {
          "SG_o": 0.8
        },
        "target": "API",
        "unit": "dimensionless",
        "value": 45.375
      },
      {
        "expression": "141.5 / SG_o - 131.5",
        "intermediates": {},
        "inputs": {
          "SG_o": 0.85
        },
        "target": "API",
        "unit": "dimensionless",
        "value": 34.970588235294116
      },
      {
        "expression": "141.5 / SG_o - 131.5",
        "intermediates": {},
        "inputs": {
          "SG_o": 0.9
        },
        "target": "API",
        "unit": "dimensionless",
        "value": 25.72222222222223
      },
      {
        "expression": "141.5 / SG_o - 131.5",
        "intermediates": {},
        "inputs": {
          "SG_o": 1
        },
        "target": "API",
        "unit": "dimensionless",
        "value": 10
      }
    ]
  }
}