Synthesis of phosphoric acid (orthophosphoric acid)

Preparation of phosphoric acid

Preparation of orthophosphoric acid by reacting disodium phosphate with gaseous hydrogen chloride

Preparation of phosphoric acid by reacting disodium phosphate with gaseous hydrogen chloride

Preparation of orthophosphoric acid by reacting disodium phosphate with gaseous hydrogen chloride

Orthophosphoric acid could be prepared by passing dry gaseous hydrogen chloride through crystals of disodium phosphate. The syrupy orthophosphoric acid is filtered in order to remove sodium chloride. An excess of hydrogen chloride could be removed by heating orthophosphoric acid the mixture until the elimination of the hydrogen chloride is complete. Prolonged heating, particularly over 180° C, should be avoided as orthophosphoric acid dehydrates forming the pyrophosphoric acid (H4P2O7). In this manner, syrupy orthophosphoric acid in an amount corresponding with a yield of 75%, of the theoretical quantity is obtained.

Preparation of orthophosphoric acid from calcium phosphate and hydrofluoric acid

Preparation of phosphoric acid from calcium phosphate and hydrofluoric acid

Preparation of orthophosphoric acid from calcium phosphate and hydrofluoric acid

Pure orthophosphoric acid may also be obtained when powdered calcium phosphate (Ca3(PO4)2) is added gradually to a slight excess of hydrofluoric acid diluted with an equal volume of water, and contained in a plastic (polytetrafluoroethylene; high density polyethylene) or nickel (platinum) vessel. The reaction mixture must be thoroughly stirred or agitated and when the reaction starts a considerable amount of heat is evaluated. When the reaction moderates, the liquid is gently heated, water being added to make up for loss by evaporation. When the liquid becomes viscous, the excess of hydrogen fluoride begins to escape, and the mixture is heated until the elimination of the acid is complete, yielding the syrupy liquid of orthophosphoric acid. If pure calcium phosphate and hydrofluoric acid are used, the orthophosphoric acid obtained by described method is very pure.

Preparation of orthophosphoric acid by oxidizing phosphorus with nitric acid

Preparation of phosphoric acid by oxidizing phosphorus with nitric acid

Preparation of orthophosphoric acid by oxidizing phosphorus with nitric acid

Before the synthesis, phosphorus is properly washed with water until decanted water shows no acid reaction. Additionally phosphorus is washed with ethyl alcohol, ether and dried. 127 g of dry red phosphorus (white/yellow phosphorus also could be used) with 1400 ml diluted (33%) nitric acid (d=1.20 g/ml) in an large round-bottom flask with reflux condenser. When the reaction begins the phosphorus melts, and then the operation quietly proceeds. After 10 to 12 hours the phosphorus has passed entirely into solution, this solution is evaporated until a sample taken out with a glass rod together with concentrated sulfuric acid and ferrous sulfate solution ceases to give a reaction for nitric acid. During the heating and evaporation process the temperature must not exceed 180° C.

Laboratory manual of inorganic preparations, by H. T. Vulte, 129-131, 1895


orthophosphoric acid



InChI Key


Canonical SMILES


MeSH Synonyms

Concise etchant, K-etchant, orthoorthophosphoric acid, orthophosphoric acid, Uni-Etch

Depositor-Supplied Synonyms

orthophosphoric acid, ORTHOorthophosphoric acid, Phosphorsaeure, Sonac, 7664-38-2, Acidum phosphoricum, Evits, Wc-reiniger, Acide phosphorique, o-orthophosphoric acid, White orthophosphoric acid, Phosphorsaeureloesungen, Acido fosforico, Acido fosforico [Italian], Fosforzuuroplossingen, Fosforzuuroplossingen [Dutch], Phosphorsaeureloesungen [German], Caswell No. 662, orthophosphoric acid, ortho-, POLYorthophosphoric acid, Acide phosphorique [French], H3PO4, UNII-E4GA8884NN, FEMA No. 2900, CCRIS 2949, CHEBI:26078, HSDB 1187, NBIIXXVUZAFLBC-UHFFFAOYSA-N, EINECS 231-633-2, NSC 80804, UN1805, EPA Pesticide Chemical Code 076001, NCGC00091005-01, orthophosphoric acid solution, DSSTox_CID_4263, DSSTox_RID_77346, DSSTox_GSID_24263, acide phosphorique (FRENCH), CAS-7664-38-2, Phospholeum, Marphos, OyAxEa, Orthophosphoricacid, phosphate monoesters, Superorthophosphoric acid, ortho orthophosphoric acid, ortho-orthophosphoric acid, diphosphate tetrasodium, poly(orthophosphoric acid), tetraoxoorthophosphoric acid, ortho- orthophosphoric acid, orthophosphoric acid (NF), ACMC-20heq4, orthophosphoric acid, 85%, Orthophosphoric monoester, orthophosphoric acid monoester, Condensed orthophosphoric acid, orthophosphoric monoesters, phosphate monoester (0), AC1L1AIN, trihydroxidooxidophosphorus, tetra-Sodium pyrophosphate, PO4-PHS, Phosphate Ionphosphate Ion, AC1Q7DL7, CHEMBL1187, orthophosphoric acid, ACS, orthophosphoric acid- D3, 40266_ALDRICH, 40278_ALDRICH, 40297_ALDRICH, 40299_ALDRICH, P5811_SIGMA, W290017_ALDRICH, D-Mannan, dihydrogen phosphate, 04102_RIEDEL, 04107_RIEDEL, 30417_RIEDEL, 345245_ALDRICH, 40266_RIEDEL, 40278_RIEDEL, 40297_RIEDEL, 40299_RIEDEL, 452289_ALDRICH, 466123_ALDRICH, 612162_ALDRICH, CHEBI:7794, E4GA8884NN, [PO(OH)3], 03366_FLUKA, 03367_FLUKA, 64957_FLUKA, 79606_FLUKA, 79607_FLUKA, 79614_FLUKA, 79617_FLUKA, 79617_SIGMA, 79621_FLUKA, 79623_FLUKA, 79626_FLUKA, CHEBI:52641, CTK2H7098, HMDB02142, trihydrogen tetraoxophosphate(3-), MolPort-003-925-287, 04102_SIAL, 04107_SIAL, 30417_SIAL, 79621_SIAL, 79623_SIAL, orthophosphoric acid (ACD/Name 4.0), 215104_SIAL, 438081_SIAL, NSC80804, Tetrasodium pyrophosphate 10-hydrate, Tox21_111053, Tox21_202285, Tox21_303246, ANW-44010, NSC-80804, Buffer concentrate from orthophosphoric acid, LS-2425, MCULE-5726619687, RP18632, NCGC00091005-02, NCGC00257071-01, NCGC00259834-01, orthophosphoric acid [UN1805] [Corrosive], 68891-72-5, E338, Isooctanol, reaction products with phosphorus oxide (P2O5) and polyethylene glycol monotridecyl ether, orthophosphoric acid [UN1805] [Corrosive], Sodium pyrophosphate decahydrate BioChemica, P1745, Phosphate standard concentrate 1.00 g PO43-, D05467, Phosphate standard concentrate 10.00 g PO43-, 3B4-1603, 3B4-1628, 730A9101-D5DE-4668-97CA-7B6178B84417, 1339-32-8, 178560-73-1, 28602-75-7, 9044-08-0

Removed Synonyms

phosphate, orthophosphate, phosphomannan, pyrophosphate, Phosphonate, Concise etchant, Phosphonic acid, Hydrogen phosphate, Phosphate ion, Unknown Ligand, K-etchant, Uni-Etch, pyrophosphate 2-, Polyorthophosphoric acids, Sodium pyrophosphate, O-Phosphoethanolamine, HYPOPHOSPHITE, PHOSPHITE ION, phosphatidylethanolamine, uridine-5′-monophosphate, HYDROGENPHOSPHATE ION, DIHYDROGENPHOSPHATE ION, Sodium pyrophosphate decahydrate, CID1004, THYMIDINE-5′-TRIPHOSPHATE, Tetrasodium Pyrophosphate Decahydrate, Phosphate Group Bonded To Thr E 197, 1,2-Dimyristoyl-sn-glycero-3-phosphocholine, 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine, C00009, C030242, 14335-33-2, 2HP, 2PO, 37267-86-0, 5GP, 8017-16-1, C5P, CP, NFB, PEE, PHS, Pi, PO2, PO3, PO4, POP, PPV, PSE, PX4, TTP, U5P, UNL

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