Sodium orthophosphate, secondary

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. 

Disodium hydrogen phosphate disodium phosphate E339 phosphoric acid, disodium salt secondary sodium phosphate sodium orthophosphate. 

The three salts are also known by a number of other names, such as NaH2P04 primary sodium phosphate, primary sodium orthophosphate, sodium biphosphate, MSP Na2HP04 secondary sodium phosphate, secondary sodium orthophosphate,... 

The orthophosphates.—Orthophosphoric acid forms three salts, normal or tertiary, secondary, and primary phosphates, according as all, two, or one of its hydrogen atoms is replaced by an equivalent radicle.26 The hydrogen atoms may be replaced by different radicles. Thus, the secondary acid salt—ammonium sodium hydrogen phosphate, also called microcosmic salt—is illustrated by the subjoined graphic formula along with the formulae for the acid and the primary, secondary, and tertiary sodium salts ... 

Synonyms Disodium orthophosphate, Disodium phosphate, DSP, Secondary sodium phosphate. 

Orthophosphoric acid is a tribasic acid giving rise to three series of salts primary orthophosphates, e.g. NaH2P04 secondary orthophosphates, e.g. Na2HP04 and tertiary orthophosphates, e.g. Na3P04. If a solution of orthophosphoric acid is neutralized with sodium hydroxide solution using methyl orange as indicator, the neutral point is reached when the acid is converted into the primary phosphate with phenolphthalein as indicator, the solution will react neutral when the secondary phosphate is formed ... 

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