Lead vanadate

The environment and oxidation state of iron in borosilicate glasses has been probed by IR, Raman, and Mossbauer spectroscopies, in lead vanadate (Pb2V207) glasses by XRD and IR and Raman spectroscopies. " ... 

Lead Metavanadate, Pb(VOg)2.—Acid solutions of vanadates on being treated with lead salts give rise to yellow basic vanadates the composition of which varies with the conditions. The precipitation of normal lead vanadate is, therefore, difficult. It has been accomplished by the addition of lead acetate to ammonium metavanadate solution in the presence of acetic acid.2 The lead precipitates contain all the vanadic acid originally present in solution, and precipitation of vanadates with lead salts has, therefore, been employed for the quantitative estimation of vanadium.3 The mineral deschenite consists chiefly of lead metavanadate a portion of the lead is, however, frequently replaced by zinc.4... 

Gravimetric Methods.—The vanadium compound is converted into sodium vanadate by fusion or other method, and after separation from other salts (e.g. arsenate, molybdate, phosphate, chromate, tungstate) is precipitated from nearly neutral solution either as (a) mercurous vanadate or (b) basic lead vanadate. In (a), mercurous... 

A general method for the separation of vanadium from arsenic, molybdenum, phosphorus, chromium, uranium, tungsten, and silicon, consists in precipitating these metals as their respective lead salts and digesting the precipitate with potassium carbonate, whereupon all the lead salts are decomposed with the exception of the lead vanadate.5... 

VANADINITE. The mineral vanadimte corresponds to the formula Pb VO Cl, being composed of lead chloride and lead vanadate in the proportion of 90.2% of the former and 9.8% of the latter. It crystallizes in the hexagonal system, is usually prismatic, but the ciystals are often skeletal or cavernous it may be found in crusts. Its fracture is uneven brittle hardness. 2.75-3 specific gravity. 6.86 fresh fractures show a resinous luster color, yellow, yellowish-brown, reddish-brown, and red streak, white to yellowish translucent to opaque. Vanadinite, not a common mineral, occurs as an alteration product in lead deposits. It is found in the Ural Mountains, Austria, Spain, Scotland, Morocco, the Transvaal, Argentina, and Mexico, In the United States it occurs in Arizona, New Mexico, and South Dakota, It is used as an ore of vanadium and to some extent of lead as well. It is interesting to note that this mineral was first described as a chromate upon its discovery in Mexico in 1801, It was not until the discovery of the element vanadium in 1830 that the true nature of this compound was known. 

In certain instances of poisoning, especially in the case of base metal catalysts, the deactivation can be simply explained by the formation of new bulk solid phases between the base metal and the poison. Examples are the formation of lead vanadates (14) in vanadia catalysts, or of sulfates in copper-chromite and other base metal catalysts (81). These catalyti-cally inactive phases are identifiable by X-ray diffraction. Often, the conditions under which deactivation occurs coincide with the conditions of stability of these inert phases. Thus, a base metal catalyst, deactivated as a sulfate, can be reactivated by bringing it to conditions where the sulfate becomes thermodynamically unstable (45). In noble metal catalysts the interaction is assumed to be, in general, confined to the surface, although bulk interactions have also been postulated. 

Lead acetate solution yellow precipitate of lead vanadate, turning white or pale yellow on standing the precipitate is insoluble in dilute acetic acid but soluble in dilute nitric acid. 

Bismuth and lead vanadates 260-380 Toluene Benzoic acid naphthalene (S3)... 

Lead vanadate — — Naphthalene Phthalic acid Toluene Benzoic acid (29) (48)... 

Bismuth and lead vanadates Manganese and lead vanadates Pumice Pumice 400-450 Benzene Benzaldehyde 290-420 Naphthalene Acetaldehyde Cyclohexane Phthalic Decalin anhydride (38)... 

Dong Z, White TJ, Wei B, Laursen K (in press) Model apatite systems for the stabilization of toxic metals I, calcium lead vanadate. J Am Ceram Soc... 

Lead acetate, Pb(CH3C02)2, forms a basic lead vanadate, yellow, turning to white on standing Precipitation can be made quantitative. 

Identification of vanadinite (lead vanadate) has been made during analysis of 22 Greek steles in the Louvre (Rouveret and Walter, 1998 Walter et al., 1998) the normally orange-red to orange-yellow compoimd had deteriorated in this instance to black. 

Oxides Vanadates) bismuth vanadate (BiV04) chnobisvanite (BiV04) copper vanadate dreyerite (BiV04) lead vanadate (Pb5(V04)3Cl) pucherite (BiV04) vanadinite (Pb5(V04)3Cl). 

---