:Octadecylphosphonic acid
{{notability|date=June 2015}}
{{Chembox
| ImageFile =Octadecylphosphonic acid.svg
| ImageSize =
| ImageAlt =
| PIN =Octadecylphosphonic acid
| OtherNames = n-Octadecylphosphonic acid, ODPA
|Section1={{Chembox Identifiers
| CASNo =4724-47-4
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = KDX6MSF5PN
| PubChem =78451
| SMILES = CCCCCCCCCCCCCCCCCCP(=O)(O)O
| ChemSpiderID = 70816
| InChI = 1/C18H39O3P/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-22(19,20)21/h2-18H2,1H3,(H2,19,20,21)
| InChIKey = FTMKAMVLFVRZQX-UHFFFAOYAI
| StdInChI = 1S/C18H39O3P/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-22(19,20)21/h2-18H2,1H3,(H2,19,20,21)
| StdInChIKey = FTMKAMVLFVRZQX-UHFFFAOYSA-N}}
|Section2={{Chembox Properties
| Formula =C18H39O3P
| MolarMass =334.474222 [g/mol]
| Appearance = White to off-white powder
| Density =
| MeltingPt = 95-100 °C
| BoilingPt =
| Solubility = Immiscible with water}}
|Section3={{Chembox Hazards
| MainHazards =
| FlashPt =
| AutoignitionPt = }}
}}
Octadecylphosphonic acid (C18H39O3P) is a chemical compound used in thermal paper for receipts, adding machines and tickets.{{Cite web |title=4724-47-4 - n-Octadecylphosphonic acid, 97% |url=https://www.alfa.com/en/catalog/020645/}}