Orthophosphoric acid, 131

Submitted by Abthur G. Weber J and G. B. King ft Checked by Laurence L. Qttill and Wilford H. Thomas  

Orthophosphoric acid of a high degree of purity may be prepared by crystallizing the acid from concentrated solutions. These solutions are obtained by removing water from ordinary syrupy phosphoric acid at low temperature and pressure. This concentration must be performed with care, since the incomplete removal of water results in the 

Place 5 lb. of 85 per cent commercial syrupy orthophosphoric acid in a 5-1., round-bottom flask equipped with a condenser and suction flask and arranged, as shown in Fig. 17, in such a way that air dried by conducting it 

To crystallize the concentrated residue, seed with a crystal of the acid, obtained by supercooling a portion of the concentrated acid in an ice bath. The temperature should be maintained at about 30°C. throughout the crystallization. 

After approximately one-third of the material has crystallized, drain the mother liquor from the crystals in an anhydrous atmosphere. To obtain a very dry acid, recrystallization is necessary. Dry the solid acid by drawing very dry air at low pressure through the crystals for several days. 

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Phosphoric acid. The commercial syrupy orthophosphoric acid has a sp. gr. of 1-75 and contains about 88 per cent, of H3PO4. An approximately 100 per cent, acid is also marketed. 

In a 500 ml. three-necked flask, equipped with a thermometer, a sealed Hershberg stirrer and a reflux condenser, place 32-5 g. of phosphoric oxide and add 115-5 g. (67-5 ml.) of 85 per cent, orthophosphoric acid (1). When the stirred mixture has cooled to room temperature, introduce 166 g. of potassium iodide and 22-5 g. of redistilled 1 4-butanediol (b.p. 228-230° or 133-135°/18 mm.). Heat the mixture with stirring at 100-120° for 4 hours. Cool the stirred mixture to room temperature and add 75 ml. of water and 125 ml. of ether. Separate the ethereal layer, decolourise it by shaking with 25 ml. of 10 per cent, sodium thiosulphate solution, wash with 100 ml. of cold, saturated sodium chloride solution, and dry with anhydrous magnesium sulphate. Remove the ether by flash distillation (Section 11,13 compare Fig. II, 13, 4) on a steam bath and distil the residue from a Claisen flask with fractionating side arm under diminished pressure. Collect the 1 4-diiodobutane at 110°/6 mm. the yield is 65 g. 

Acetylthiophene Is prepared by the acetylation of thiophene with acetic anhydride In the presence of orthophosphoric acid ... 

Solubility in syrupy phosphoric acid. This test should only be apphed if the compound is soluble in concentrated sulphuric acid. Place 3 0 ml. of 85 per cent, orthophosphoric acid in a dry test-tube and add 0 10 g. of a solid or 0 - 20 ml. of a Liquid. If the compound does not dissolve immediately, agitate for some time but do not boil. 

H3PO4 orthophosphoric acid (or H2Se03 selenious acid... 

Filter acid from a dihydrate process contains 28—32% P2 5 usually concentrated to 40—45% P2 s when used at the site for fertilizer production. For shipping, the acid is concentrated to 52—54% P2 5 these concentrations the product is orthophosphoric acid [7664-38-2] ... 

Fig. 25. TVA pipe reactor process for production of 9-32-0 and 12-36-0 grade base suspensions directly from wet-process orthophosphoric acid.

All three fluorophosphoric acids are commercially available. The mono- and difluoro acids can be made as anhydrous or hydrated Hquids. Commercial hexafluorophosphoric acid is an aqueous solution. Anhydrous hexafluorophosphoric acid maybe prepared at reduced temperatures and pressures but it dissociates rapidly into PF and HF at 25°C (56). When diluted with water all the fluorophosphoric acids hydrolyze producing orthophosphoric acid. The hexafluoro acid is the most stable of the three fluorophosphoric acids. 

Evaporated milk is a Hquid product obtained by the partial removal of water only from milk. It has a minimum milk-fat content of 7.5 mol % and a minimum milk-solids content of 25.0 mol %. Evaporated skimmed milk is a Hquid product obtained by the partial removal of water only from skimmed milk. It has a minimum milk-solids content of 20.0 mol %. Sweetened condensed milk is a product obtained by the partial removal of water only from milk with the addition of sugars. It has a minimum milk-fat content of 8.0 mol % and a minimum milk-solids content of 28.0 mol %. Skimmed sweetened condensed milk is a product obtained by the partial removal of water only from skimmed milk with the addition of sugars. It has a minimum milk-solids content of 24.0 mol %. AH may contain food additives (qv) as stabilizers, in maximum amounts, including sodium, potassium, and calcium salts of hydrochloric acid at 2000 mg/kg singly citric acid, carbonic acid, orthophosphoric acid, and polyphosphoric acid at 3000 mg/kg in combination, expressed as anhydrous substances and in the evaporated milk carrageenin may be added at 150 mg/kg. 

Fig. 1. Titration curve of orthophosphoric acid in the presence of sodium hydroxide.

At equihbrium, the specific composition of a concentrated phosphoric acid is a function of its P2 s content. Phosphoric acid solutions up to a concentration equivalent of about 94% H PO (68% P2O5) contain H PO as the only phosphoric acid species present. At higher concentrations, the orthophosphoric acid undergoes condensation (polymerization by dehydration) to yield a mixture of phosphoric acid species (Table 5), often referred to genericaHy as polyphosphoric or superphosphoric acid, H20/P20 = - 3, or ultraphosphoric acid, H20/P20 = - 1. At the theoretical P2O5 concentration for orthophosphoric acid of 72.4%, the solution is actually a mixture containing 13% pyrophosphoric acid and about 1% free water. Because the pyrophosphoric acid present is the result of an equihbrium state dependent on the P2 5 content of the solution, pure orthophosphoric acid can be obtained because of a shift in equihbrium back to H PO upon crystallization. 

Orthophosphate salts are generally prepared by the partial or total neutralization of orthophosphoric acid. Phase equiUbrium diagrams are particularly usehil in identifying conditions for the preparation of particular phosphate salts. The solution properties of orthophosphate salts of monovalent cations are distincdy different from those of the polyvalent cations, the latter exhibiting incongment solubiUty in most cases. The commercial phosphates include alkah metal, alkaline-earth, heavy metal, mixed metal, and ammonium salts of phosphoric acid. Sodium phosphates are the most important, followed by calcium, ammonium, and potassium salts. 

The hydrolysis of phosphoms sulfides has been studied quantitatively. A number of products are formed (Table 6). Whereas phosphoms(V) sulfide reacts slowly with cold water, the reaction is more rapid upon heating, producing mainly hydrogen sulfide and orthophosphoric acid, H2PO4. At high pH, P4S Q hydroly2es to a mixture of products containing thiophosphates and sulfides. 

H PO is therefore a stronger acid than orthophosphoric acid. The second dissociation constant, pR 2> Th third hydrogen does not ionize in... 

These precursors are prepared by reaction of fuming nitric acid in excess acetic anhydride at low temperatures with 2-furancarboxaldehyde [98-01-1] (furfural) or its diacetate (16) followed by treatment of an intermediate 2-acetoxy-2,5-dihydrofuran [63848-92-0] with pyridine (17). This process has been improved by the use of concentrated nitric acid (18,19), as well as catalytic amounts of phosphoms pentoxide, trichloride, and oxychloride (20), and sulfuric acid (21). Orthophosphoric acid, -toluenesulfonic acid, arsenic acid, boric acid, and stibonic acid, among others are useful additives for the nitration of furfural with acetyl nitrate. Hydrolysis of 5-nitro-2-furancarboxyaldehyde diacetate [92-55-7] with aqueous mineral acids provides the aldehyde which is suitable for use without additional purification. 

Manufacture of 2-acetylthiophenes involves direct reaction of thiophene or alkylthiophene with acetic anhydride or acetyl chloride. Preferred systems use acetic anhydride and have involved iodine or orthophosphoric acid as catalysts. The former catalyst leads to simpler workup, but has the disadvantage of leading to a higher level of 3-isomer in the product. Processes claiming very low levels of 3-isomer operate with catalysts that are proprietary, though levels of less than 0.5% are not easily attained. 

H1C phosphate orthophosphoric acid (AP+ andZn"+) calcined 2inc oxide, calcined magnesium oxide oxides phosphate luting agent, base... 

A mixture of 85% orthophosphoric acid (4 parts) and metaphosphoric acid (1 part)... 

Phosphorus exists as white and red phosphorus. The former allotrope may be preserved in the dark at low temperatures but otherwise reverts to the more stable red form. The white form is a waxy, translucent, crystalline, highly-toxic solid subliming at room temperature and inflaming in air at 35°C, so it is handled under water. The red form is a reddish violet crystalline solid which vaporizes if heated at atmospheric pressure and condenses to give white phosphorus. The red form ignites in air at 260°C. Both are insoluble in water, and white phosphorus can be stored beneath it. Phosphorus forms a host of compounds such as phosphine, tri- and penta-halides, tri-, tetra- and penta-oxides, oxyacids including hypophosphorous, orthophosphorous and orthophosphoric acids. 

Chemical Designations - Synonyms Orthophosphoric acid Chemical Formula H3PO4. 

Spray solution For sugars [3] dissolve 3 g 2-aminodiphenyl in 100 ml glacial acetic acid and add 1.5 ml 85% orthophosphoric acid. 

Substances Biphenyl-2-ylamine Sulfuric acid (25%) Ethanol Glacial acetic acid Orthophosphoric acid (85%)... 

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