Orthovanadic acid

Silver orthovanadate reacts with alkyl halides to give esters of vanadic acid. These are yellow liquids of general formula Alk.3V04, in which Aik. represents the alkyl radical. Esters of orthovanadic acid axe more stable than those of pyro- and meta-vanadic acids that is, the order of stability is the reverse of that which applies to the inorganic salts.3 The following orthovanadates have been prepared —... 

Halides and Esters Derived from Orthovanadic Acid... 

Formal substitution of three OH groups in hypothetical orthovanadic acid H3V04[0= V(0H)3] for halide leads to the trihalides VOX3 (X = F, Cl, Br). The corresponding nitrate V0(N03)3 is aiso known. The oxovanadium trihalides can add an additional... 

As pointed out in the previous section, phosphate derivatives related to H3VO4 are of interest when it comes to the phosphate-vanadate antagonism. Similarly, vanadate esters are analogues of phosphate esters (Section 5.2.1). Esters of orthovanadic acid have been known since IQIS.I They are obtained by, e. g., condensation of vanadates and alcohols (ROH) in aqueous media [Equation (2.11)], alcoholysis of VOCI3 [Equation (2.12)] or the reaction of vanadium pentoxide and alcohols in the presence of water scavengers [Equation (2.13)]. The triesters are sensitive to moisture. The primary product of hydrolysis is the hexavanadic acid derivative V50i3(0R)4, giving rise to a yellow colouration as the colourless triesters come into contact with moist air. 

General.—It seems certain that the free acids corresponding to these salts do not exist in the solid state, and that, with the possible exception of hexavanadic acid, mentioned below, they are also incapable of existing in solution, although salts of all the acids are known. The most stable class of salts is the metavanadates, the next in order of stability being the pyrovanadates, while the orthovanadates are few in number and undergo rapid hydrolysis even in the cold, to give the pyro-salts ... 

Silver Ortliovanadate, Ag3V04, is precipitated as a deep orange powder when a freshly prepared solution of sodium orthovanadate is treated with a carefully neutralised solution of silver nitrate. It melts between 408° and 565° C.,7 and is soluble in nitric acid and in ammonium hydroxide the latter solution yields yellow hexagonal crystals of the composition 3AgV03.2NH3.H20.8... 

Samarium Polyvanadates.—Addition of a neutral samarium salt to a solution of a metavanadate throws down a yellow, amorphous precipitate which consists mainly of samarium orthovanadate. Two acid... 

The solution chemistry of the rare earth vanadates has received considerable attention [359,360]. It has been found that when ammonium metavanadate solution is added to rare earth nitrate solutions, an increase in acidity results with the formation of the orthovanadates (eq. 35). However, when the solutions are mixed in the opposite order the pH of the medium remains unchanged and precipitates of metavanadates the (eq. 36) are produced. 

V2O5 is slightly soluble in water, producing a pale yellow, acidic solution that readily becomes colloidal, hi alkalis, it dissolves to form colorless solutions, the nature of the species present depending upon the pH. At high pH, the orthovanadate ion [V04] is formed, and at intermediate... 

SYNS SODIUM VANADATE SODIUM VANADIUM OXIDE TRISODIUM ORTHOVANADATE VANADICai) ACID, TRISODIUM SALT... 

TRISODIUM NITRILOTRIACETATE see SIP500 TRISODIUM NITRILOTRIACETATE MONOHYDRATE see NEIOOO TRISODIUM NITRILOTRIACETIC ACID see SIP500 TRISODIUM ORTHOPHOSPHATE see SJH200 TRISODIUM ORTHOVANADATE see SIY250 TRISODIUM PHOSPHATE see SJH200... 

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