Lead, divalent

Curve B describes the corresponding relation for the oxidation of divalent lead ions Pb2+ -> Pb4+, which implies the formation of lead dioxide since Pb4+ does not exist alone ... 

FIGURE 20.6 Distribution of molecular and ionic species of divalent lead at different pH values. (From U.S. EPA, Assessing the Geochemical Fate of Deep-Well-Injected Hazardous Waste A Reference Guide, EPA/625/6-89/025a, U.S. EPA, Cincinnati, OH, June 1990.)... 

Divalent lead can interfere with the action of other divalent cations, such as Ca+2, in biological systems. 

This dye fluoresces after binding Pb+2 and Ca+2 lead is considered an interferant to the determination of calcium by this approach. However, by complexing the divalent lead ion with the heavy metal chelator TPEN (N,N,N ,N -tetrakis(2-pyridylmethyl)ethylene-diamine) prior to the addition of the fluo-3, the fluorescent... 

If lead nitrate is used rather than the chloride or acetate as the source of divalent lead, the crude dicyclopentadienyllead may explode violently during purification by high-vacuum sublimation at 100-130°C. 

Derivatives of divalent lead 1.3- Dithia-2-plumba(II)-cyclopentene Benzo-1,3,2-dithiaplumb(II)ole 1.3- Dithia-2-plumba(II)-cyclopentane 1.3- Diaza-4,5-disila-2-plumba(lI)-cyclopentane 89ZN(B)1531 85JOM(290)41 91MI 424-03 90ICA205... 

Good yields are obtained only if the oxidation of the divalent lead to the tetravalent stage is complete. To test for plumbous lead, add ten drops of the reaction mixture to five milliliters of water and boil gently for a few minutes to hydrolyze all the tetravalent lead to lead dioxide. When the latter settles, filter the hot mixture, cool under the tap, and add several drops of saturated potassium iodide. A yellow precipitate of lead iodide constitutes a positive test. 

Lead nithopluiuhaie, Pb-PbOj, ted lead, is similarly described ns a sail, in Ihi.s ease an orihoplumbalc of divalent lead. Pb PbO i. because on treatment with nitric acid, two-thirds of the lead dissolves and one third remains us PbO . It is prepared in the red farm by atmospheric heating of PbO. and in a black form by reaction nl" pbO with pure oxygen. Red lead is formed of PhOj, octahedra (with one common edge I linked by lead atoms covalently bonded to three oxygen atoms. 

In preparative experiments, excess lead tetraacetate may be smoothly reduced by addition of a stoichiometric quantity of hydrazine in acetic acid.43 Oxalic acid is also useful,28 additional acid being added to precipitate the divalent lead formed. When no excess of tetravalent lead is present, sulfuric acid, oxalic acid, or a cation-exchange resin may be used for removing divalent lead. 

The non-bonding lone pair s-electrons of such ions as divalent lead and divalent tin generate a series of strongly localized states which can be pumped and which emit a broad band luminescence typically in the range of 360 to 500 nm. 

A unique type of R2Pb compound is the cyclopentadienyl derivative of divalent lead. Only two such compounds are known, bis(cyclopenta-dienyl)lead and bis(methylcyclopentadienyl)lead. From dipole moments and infrared and NMR spectra, these compounds are postulated to possess a sandwich-type configuration, similar to that of ferrocene and the other metallocenes, but one in which the cyclopentadienyl rings are located angularly about the lead atom. This type of structure is the first... 

Are lead salts (nitrate or chloride) appreciably hydrolyzed in aqueous solution Compare the basic strength of the hydroxide of divalent lead with that of aluminum hydroxide. 

Chlorine in alkaline solution oxidizes the divalent lead to tetra-valent, the latter appearing as the very insoluble brown Pb02... 

The nitrosation is effected in a well known way. A weak (2.75%) aqueous solution of one mole of resorcinol is acidified with 2 moles of sulphuric acid. The solution is cooled down to -2°C and a 10% aqueous solution of 2 moles of NaN02 is added, dropwise. Crystalline yellowish 2,4-dinitrosoresorcinol is precipitated in theoretical yield. The precipitate is washed and separated in a centrifuge or on a vacuum filter prior to oxidation. From dinitrosoresorcinol the divalent lead salt of dinitrosoresorcinol may be prepared, having initiating properties. 

For the preparation of the divalent lead salt a moist product is used its water content should be determined exactly. 

The electrodeposition of lead, Pb, has been investigated in an acidic EMICl-AICI3 ionic liquid [27]. A divalent lead species, Pb(II), can be introduced by dissolving lead dichloride, PbCl2, or the anodic dissolution of metallic Pb. Metallic Pb is obtained by the reduction of Pb(II) ... 

A number of reviews dealing with organoplumbanes have been published,however, and the purpose of this contribution is to overview the advances in organometalhc chemistry of lead in the last decade for both divalent lead, R2Pb, and tetravalent lead, R4 PbX . 

Sn, Pb) and the synthetic methods for plumbylenes are restricted mainly to nncleophilic snbstitntion of divalent lead halides and amides with organolithium or Grignard... 

A similar difference in M-0 bond character presumably exists in oxy-compounds of divalent lead. Many anhydrous oxy-salts of Pb are isostructural with those of Ba (and sometimes Sr and Ca) ... 

Adenosine 5 -phosphorimidazolidate condenses in aqueous solution in the presence of divalent metal ions to form oligo(adenylic acid). Using divalent lead ions, as much as 57% condensation to oligo(A) has been reported studies on the di-and tri-nucleotide with RNase Tg show the internucleotide bonds to be mainly 2 ->5 -linked. The metals most efficient in catalysing condensation occupy an intermediate position in the classification as hard and soft acids and bases, and it is thought that they may co-ordinate to both base and phosphate. 

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