Vapor Pressure API
Vapor-pressure thermodynamics as an API, computed locally and deterministically. The clausius-clapeyron endpoint predicts the vapor pressure of a substance at a new temperature from a known reference point and the molar enthalpy of vaporization, using ln(P2/P1) = -ΔHvap/R·(1/T2 - 1/T1) with temperatures in kelvin — so from water boiling at 101.325 kPa at 373.15 K and ΔHvap ≈ 40.66 kJ/mol it returns about 42.6 kPa at 350 K. The enthalpy endpoint inverts the same relation: given two pressure/temperature points it solves for the molar enthalpy of vaporization, ΔHvap = -R·ln(P2/P1)/(1/T2 - 1/T1), in J/mol and kJ/mol. The antoine endpoint evaluates the Antoine equation log10(P) = A - B/(C + T) both ways — supply a temperature to get the vapor pressure, or a pressure to get the boiling temperature — defaulting to the water constants (°C and mmHg, so water reads 760 mmHg at 100 °C) but accepting any A, B, C for other substances. The gas constant R = 8.314462618 J/(mol·K). Everything is computed locally and deterministically, so it is instant and private. Ideal for chemical-engineering, process-simulation, distillation, HVAC, meteorology and chemistry-education app developers, boiling-point and phase-equilibrium tools, and lab software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is vapor pressure and boiling point; for humidity and dew point use a psychrometric API and for ideal-gas state use a gas-law API.
api.oanor.com/vaporpressure-api
