Silver orthophosphate

Silver Phosphates. Silver phosphate [7784-09-0], or silver orthophosphate, Ag3P04, is a bright yellow material formed by treating silver nitrate with a soluble phosphate salt or phosphoric acid. Silver pyrophosphate [13465-97-9], is a white salt prepared by the addition of a soluble... 

Silver nitrate Orthophosphates, P043- Yellow precipitate of silver orthophosphate soluble in dilute ammonia and in dilute nitric acid... 

The calcium salt of 2-amino-2-deoxy-D-glucosyl phosphate has been synthesized37 by the interaction of 2-acetamido-3,4,6-tri-0-acetyI-2-deoxy-a-D-glucosyl chloride with silver orthophosphate, with subsequent partial saponification. On the basis of optical rotation, the derivative has been assigned to the a-n series. 2-Amino-2-deoxy-D-glucosyl phosphate is much less stable than the 6-phosphate toward acidic hydrolysis, but it is markedly more... 

Silver orthophosphate, prepared by several methods, one of which is indicated below, was converted into silver bromide, the equations involved being —... 

The solutions which were allowed to interact were about 0-08 N in order to avoid inclusions in the precipitates. The latter were well washed, and allowed to stand in water for at least 24 hours. Silver orthophosphate was stable in the presence of the moderate amounts of acid produced by some of the reactions which were tried. If silver nitrate is poured into excess of disodium hydrogen phosphate the precipitate settles rapidly, but precipitation is incomplete. If di-sodium ammonium phosphate is poured into silver nitrate the precipitate settles rapidly and the solution remains nearly neutral, according to the equation... 

The preceding method is open to the criticism that silver orthophosphate contains only 7-4 per cent, of phosphorus. Phosphorus tribromide is somewhat better in this respect, containing 11-5 per cent, of phosphorus but on the other hand the preparation and quantitative decomposition of this compound in a manner suitable for atomic weight determinations present great difficulties, the nature of which is apparent from the following narrative.1... 

Determination of Orthophosphates.—(1) With Silver Nitrate.— This depends upon the precipitation of silver orthophosphate in solutions of low and controlled acidity. In the assay of commercial 85 per cent, phosphoric acid of density 1-710 the syrup is diluted to a convenient volume and an aliquot part is taken which contains about 0-1 gram of H3P04. It is neutralised to phenolphthalein with approximately decinormal alkali (free from chloride). 50 c.c. of decinormal silver nitrate are then added while the solution is kept neutral to litmus by stirring in zinc oxide or a suspension of the hydroxide. The whole or a measured part of the filtered solution is acidified with nitric acid and, after the addition of ferric alum, the unused silver nitrate is titrated with standard decinormal ammonium thiocyanate in the usual manner. Alkali phosphates may also be determined in this way. 

Silver nitrate solution yellow precipitate of normal silver orthophosphate, Ag3P04 (distinction from meta- and pyrophosphate), soluble in dilute ammonia solution and in dilute nitric acid. 

Silver orthophosphate, Ag3P04.—With solutions of normal or secondary sodium orthophosphate silver nitrate gives a yellow precipitate of silver orthophosphate, containing silver nitrate which cannot be removed by washing. Secondary silver orthophosphate, Ag2HP04, is obtained in white crystals from the solution of the normal orthophosphate in aqueous phosphoric acid. At 170° C. it changes to the pyrophosphate. 

Silver pyrophosphate, Ag4P207.—Precipitation of sodium pyrophosphate with silver nitrate yields the pyrophosphate in the form of a white powder, fusible at red heat. Secondary sodium orthophosphate converts it into silver orthophosphate. A double salt of the formula NaAg3P207 is also known. On heating, its colour changes from white to yellow, a phenomenon which has been attributed to decomposition into sodium metaphosphate and silver orthophosphate, but which is considered by Balareff 4 to have probably a physical origin. 

Silver orthophosphate, Ag3P04, p = 6.37 g/cc, mp = 849°C, is obtainable as an insoluble bright yellow powder from silver nitrate by the action of POCI3 (5.88), or aqueous sodium salt (14.3). It is photosensitive and turns reddish in colour, and can be reduced to metallic silver with hydrogen at 425°C. In Ag3P04 the Ag-O bonds are probably somewhat covalent, since the structure is based on tetrahedral Ag04 and PO4 units. The acid silver salt cannot be precipitated from an aqueous solution with Na2HP04 because of the relationship (5.89). 

If silver nitrate solution be added to an orthophosphate in solution, the yellow precipitate which is obtained is silver orthophosphate. With pyrophosphates and other condensed phosphates the precipitate is usually white. If an acid orthophosphate is present, nitric acid is liberated and this can be detected with litmus paper. This can be used as a method of distinguishing an acid orthophosphate... 

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