{"openapi":"3.1.0","info":{"title":"Colligative Properties API","version":"1.0.0","description":"Colligative-properties chemistry maths as an API, computed locally and deterministically. The freezing-point endpoint computes the freezing-point depression ΔTf = i·Kf·m and the resulting lowered freezing point of a solution, from the molality, the cryoscopic constant (1.86 °C·kg/mol for water) and the van 't Hoff factor i — which is 1 for a non-electrolyte like sugar, about 2 for sodium chloride and about 3 for calcium chloride. The boiling-point endpoint computes the boiling-point elevation ΔTb = i·Kb·m and the raised boiling point, with the ebullioscopic constant (0.512 °C·kg/mol for water). The osmotic-pressure endpoint computes the van 't Hoff osmotic pressure Π = i·M·R·T from the molarity, the temperature and the van 't Hoff factor, the pressure that drives osmosis across a semipermeable membrane, returned in atmospheres, kilopascals and bar. Molality is in mol per kg of solvent, molarity in mol per litre of solution and temperature in kelvin. Everything is computed locally and deterministically, so it is instant and private. Ideal for chemistry-education, food-science, antifreeze, desalination and biology app developers, solution and de-icing tools, and STEM teaching. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is colligative properties of solutions; for a compound's molar mass use a molar-mass API and for dilution concentrations a dilution API.","contact":{"name":"PremiumApi","url":"https://www.oanor.com/by/premiumapi"}},"servers":[{"url":"https://api.oanor.com/colligative-api","description":"oanor gateway"}],"tags":[{"name":"Colligative"},{"name":"Meta"}],"components":{"securitySchemes":{"oanorKey":{"type":"apiKey","in":"header","name":"x-oanor-key","description":"Get your key at https://www.oanor.com/developer/keys"}}},"security":[{"oanorKey":[]}],"paths":{"/v1/boiling-point":{"get":{"operationId":"get_v1_boiling_point","tags":["Colligative"],"summary":"Boiling-point elevation","description":"","parameters":[{"name":"molality","in":"query","required":true,"description":"Molality (mol/kg)","schema":{"type":"string"},"example":"1"},{"name":"vant_hoff_factor","in":"query","required":false,"description":"van 't Hoff factor i","schema":{"type":"string"},"example":"2"},{"name":"kb","in":"query","required":false,"description":"Ebullioscopic constant","schema":{"type":"string"},"example":"0.512"},{"name":"normal_boiling_point","in":"query","required":false,"description":"Solvent boiling point (°C)","schema":{"type":"string"},"example":"100"}],"security":[{"oanorKey":[]}],"responses":{"200":{"description":"OK","content":{"application/json":{"example":{"data":{"note":"Boiling-point elevation ΔTb = i·Kb·m raises the boiling point. 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For water Kf = 1.86 °C·kg/mol; i is 1 for non-electrolytes, ~2 for NaCl, ~3 for CaCl₂.","inputs":{"kf":1.86,"molality":1,"vant_hoff_factor":2,"normal_freezing_point_c":0},"new_freezing_point_c":-3.72,"freezing_point_depression_c":3.72},"meta":{"timestamp":"2026-06-05T11:30:32.917Z","request_id":"c7ce3322-e118-4574-bf2a-28b47aff64d6"},"status":"ok","message":"Freezing point depression","success":true}}}},"401":{"description":"Missing or invalid x-oanor-key header"},"402":{"description":"Active subscription required"},"429":{"description":"Rate-limit or monthly quota reached"},"502":{"description":"Upstream did not respond"}}}},"/v1/osmotic-pressure":{"get":{"operationId":"get_v1_osmotic_pressure","tags":["Colligative"],"summary":"Osmotic pressure","description":"","parameters":[{"name":"molarity","in":"query","required":true,"description":"Molarity (mol/L)","schema":{"type":"string"},"example":"0.1"},{"name":"vant_hoff_factor","in":"query","required":false,"description":"van 't Hoff factor i","schema":{"type":"string"},"example":"1"},{"name":"temperature","in":"query","required":false,"description":"Temperature (K)","schema":{"type":"string"},"example":"298.15"}],"security":[{"oanorKey":[]}],"responses":{"200":{"description":"OK","content":{"application/json":{"example":{"data":{"note":"Van 't Hoff osmotic pressure Π = i·M·R·T, with R = 0.082057 L·atm/(mol·K) and T in kelvin. 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