Dihydrogen Orthophosphate 1-Hydrate

SUBMITTED BY A. ToVBORG JENSEN AND J. RaTHLEV Checked by Therald Moellert and Robert W. HAiSTyf 

Calcium dihydrogen orthophosphate 1-hydrate has been reported to be deliquescent however, its alleged deliquescence may be attributed to contamination with orthophos-phoric acid. The following procedure gives a crystalline product which is perfectly stable when exposed to air. The salient point in the preparation of the stable compound is the washing of the crystals with acetone. 

Fifty grams of calcium carbonate (0.5 mol), 110 g. of 89% orthophosphoric acid (1.0 mol), and 200 ml. of 60% ortho-phosphoric acid (the liquor from the crystallization step in an earlier rim is suitable) are kneaded in a mortar until the evolution of carbon dioxide has stopped. The mixture is added to 250 ml. of 60% orthophosphoric acid. The resulting slurry is heated until the solid components dissolve and, if necessary, is filtered with suction through a funnel equipped with a sinte ed-glass disk. In order to obtain large crystals of the product, the clear solution must be cooled very slowly to 0°. The crystalline product is filtered, washed seven or eight times with 70-ml. portions of 

Calcium dihydrogen orthophosphate 1-hydrate crystallizes as large, white, shining, triclinic plates which may be up to 1 mm. in diameter. The refractive indexes for the crystals are 1.528, 1.518, and 1.501.1 No increase in weight is detectable when calcium dihydrogen orthophosphate 

1- hydrate is exposed to the air at room temperature for long periods of time. 

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Calcium dihydrogen orthophosphate 1-hydrate, synthesis 5 Calcium hydrogen orthophosphate, synthesis 6 Arsenic(III) fluoride, synthesis 50 Bismuth (III) iodide, synthesis 38 Vanadium(II) chloride, synthesis... 

CO Carbon monoxide, 2 81 CO(N3)j Carbonyl azide, 4 35 C3N3C13 Cyanuric chloride, 2 94 [C H4(OH)CH=NCH2]2 N,N -Di-salicylalethylenediamine, 3 198 CaCOa Marble, 2 49 CaP2 Calcium fluoride, 4 137 Ca(H2P04)2-H20 Calcium dihydrogen orthophosphate 1-hydrate, 4 18... 

CaC03 Marble, 2 49 CaF2 Calcium fluoride, 4 137 Ca(H2P04)2-H20 Calcium dihydrogen orthophosphate 1-hydrate, 4 18... 

Species in solution containing the PO4 species of the orthophosphates, using the ferric salts FeCl3 and Fe2(S04)3 as precipitants Milligrams per liter of snspended sohds in raw water Cubic meters of water treated Water of hydration of alnm Activity coefficient of the calcium ion Activity coefhcient of the hydrogen ion Activity coefhcient of the hydrogen phosphate ion Activity coefhcient of the dihydrogen phosphate ion Activity coefhcient of the phosphate ion... 

Disodium dihydrogen pyrophosphate dissolves slowly in cold water, a 1 per cent solution having a pH of 4.1 to 4.3. One hydrate, Na2H2P207 6Ha0, can be crystallized from aqueous solutions at slightly below room temperature. The hydrated crystals are biaxial negative with a = 1.456, jS = 1.464, and 7 = 1.465( .002). When heated they lose their water of crystallization around 36°. In aqueous solution the disodium pyrophosphate hydrolyzes to orthophosphate, the rate of hydrolysis depending on the temperature. At 70° a 1 per cent solution is hydrolyzed approximately 10 per cent in 6 hours at 100° the hydrolysis is complete in less than 6 hours. ... 

Heavy metal orthophosphates (M = Cr, Mn, Fe, Co, Ni, Zn, Hg, Pb, Ag) can be prepared in hydrated form by simple double decomposition involving aqueous solutions of an alkali hydrogen phosphate and the appropriate metal salt. Cobalt phosphate octahydrate, for example, is obtainable as a beautiful lavender-coloured precipitate from cobalt chloride and potassium dihydrogen phosphate. 

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