Tetrabase

The carbonates, sulfates, nitrates, and haUdes of lead (except the yeUow iodide) are colodess. Bivalent lead forms a soluble nitrate, chlorate, and acetate a slightly soluble chloride and an insoluble sulfate, carbonate, chromate, phosphate, molybdate, and sulfide. Highly crystalline basic lead salts of both anhydrous and hydrated types are readily formed. Tetrabasic lead sulfate [52732-72-6] 4PbO PbSO, and the hydrated tribasic salt [12397-06-7] ... 

Tetrabasic Lead Sulfate. Tetrabasic lead sulfate [12065-90-6] 4PbO PbSO, mol wt 1196.12, sp gr 8.15, is made by fusion of stoichiometric quantities of Htharge (PbO) and lead sulfate (PbSO heat of formation, Ai/ = — 1814 kJ/mol (—434.1 kcal/mol). Alternatively, tetrabasic lead sulfate may be prepared by boiling the components in aqueous suspensions. At about 70°C, tribasic hydrate reacts with lead oxide to form tetrabasic sulfate. At 80°C, this transformation is complete in - 20 hours. Tetrabasic lead sulfate is used in limited quantities in Europe as a PVC stabilizer. However, in the United States, lead-acid batteries have been developed by BeU Telephone Laboratories, which contain tetrabasic lead sulfate. Such batteries are used for emergency power at telephone switchboard stations and have an anticipated service life of over 50 years. 

Paste Mixing. The active materials for both positive and negative plates are made from the identical base materials. Lead oxide, fibers, water, and a dilute solution of sulfuric acid are combined in an agitated batch mixer or reactor to form a pastelike mixture of lead sulfates, the normal, tribasic, and tetrabasic sulfates, plus PbO, water, and free lead. The positive and negative pastes differ only in additives to the base mixture. Organic expanders, barium sulfate [7727-43-7] BaSO carbon, and occasionally mineral oil are added to the negative paste. Red lead [1314-41 -6] or minium, Pb O, is sometimes added to the positive mix. The paste for both electrodes is characterized by cube weight or density, penetration, and raw plate density. 

PbO TbSO H20. If the temperature is elevated to >57° C, the result is coarse tetrabasic lead sulfate, 4PbO TbSO, crystals. This is especially critical for the positive electrode where tribasic sulfate converts readily to Pb02 during battery formation but tetrabasic sulfate does not (93). 

In the absence of metal coordination the compound would titrate as a typical tetrabasic acid having a stepwise titration curve as shown in Figure 6. 

These compounds yield, on hydrolysis, the free acids, which, like all acids containing two carbo.xyl groups attached to the same carbon atom, lose COj on heating. Thus, ethyl malonic acid yields butyric acid. In this way the synthesis of monobasic acids may be readily effected. Malonic ester, moreover, may be used in the preparation of cyclic compounds as well as of tetrabasic and also dibasic acids of the malonic acid series ( Perkin). To give one illustration malonic ester, and ethylene bromide in presence of sodium alcoholate, yield triniethyleiic dicarbo.xylic ester and tetramethylene tetracarbo.xylic ester. The first reaction takes place in two steps,... 

As diphosphoric acid is tetrabasic, four series of salts are possible though not all are always known, even for simple cations. The most studied are those of Na, K, NH4 and Ca, e.g. ... 

Paste mixing means the addition of sulfuric acid and water. The result is a fairly stiff paste with a density between 1.1 and 1.4gcm 3 containing 8-12wt% of lead sulfate. The water content of thus mix determines the porosity of the active material achievable later (cf. "curing" below). In the paste, a mixture of lead sulfate and basic lead sulfate is formed (cf. Table 1). In the usual mixing process between room temperature and 50 °C, tribasic lead sulfate is formed. The generation of the tetrabasic... 

To a certain extent, the formation of the tetrabasic variant is desired, because 4PbO PbS04 forms fairly large crystals when transformed into lead dioxide (PbO,). This results in a mechanically stable active material, but there are disadvantages, because it is more difficult to transform this material into lead dioxide, i.e., the formation process (see below) is more expensive (and takes longer) and the initial capacity is slightly reduced (cf., e.g., Ref. [19]. For "long-life batteries" (Bell systems cell), a special process has been developed to produce pure tetrabasic material [20]. 

The novel tetrabasic ligand l,3-bis(5-methylpyrazole-3-carboxamido)propane forms a trinuc-lear Co111 Co11 Co111 complex (196). The tetradentate diamide-pyrazolyl chelates encircle the terminal trivalent metal ions while the central divalent Co is in a distorted tetrahedral environment provided by the four bridging pyrazolyl rings.881... 

The pyrophosphate buffer is of particular technical interest as it can be used over the relatively wide range of pH 3-9. Unlike the orthophosphate titration curve, that for the tetrabasic pyrophosphate system is almost straight [6]. This linearity (Figure 10.3) means that effective buffering action is available across the whole pH range simply by using various pairs of ionised components and varying their proportions even so, however, it does not seem to be widely used. 

In its unreacted form EDTA is a tetrabasic acid represented by... 

Being a tetrabasic acid, EDTA dissociates in solution to give four different ionic species, H3Y, H,Y2, Hy3-, Y4-, the relative amounts of which will depend upon the pH of the solution. The proportion of any species present is represented by its a value, an idea introduced in Chapter 3. 

Consequently the addition of the first mol. of KOH furnishes 515 Cals. the second, 21"44 Cals. the third, 3"15 Cals. and the fourth and fifth, 2-3 Cals. The mean of the first two values is 13"195, corresponding with the normal value for strongly ionized acids. This is said to be a chance result. J. Thomsen infers that periodic acid is dibasic, and writes the formula I04H3(0H)2 or better still tetrabasic I2OgH6(OH)i, and he writes the formula—oxygen quadrivalent, iodine univalent—... 

In addition to the complexes listed in Table 47, the compounds Ar,Ar -di(2-hydroxy-phenyl)ethylenediamine-lV,lV -diacetic acid and N -(2-hydroxyethyl)ethylenediamine-jV,iV,Ar-triacetic acid behave as tetrabasic ligands, forming ThLxH20 (x = 6 and 2 respectively). 

When selenic acid and molybdic acid are heated together on a water-bath for several days a compound of composition Mo03.Se03 is formed, which is obtainable as a crystalline mass,4 and which with a little water yields a hydrate, having the formula Mo03.Se03.2H20 when dried at 110° C. This compound has the properties of a tetrabasic acid. 

The product is heated in a rotary kiln causing the excess lead oxide to react with the basic lead chromate, forming tetrabasic lead chromate ... 

HI A tetraprotic system. Write an equation for the titration of tetrabasic base with strong acid (B + H+ —>— —>—> BHJj+ You can do this by inspection of Table 11-6 or you can derive it from the charge balance for the titration reaction. Use a spreadsheet to graph the titration of 50.0 mL of 0.020 0 M sodium pyrophosphate (Na4P207) with 0.100 M HC104. Pyrophosphate is the anion of pyrophosphoric acid. 

The properties of he tetrabasic acid prepared from dibroiusuceinic ester by Perjcin differed from the acids obtained in other ways. Buchner repeated this work,however,and got only the jcnown acid. (Of.note on page HS. ) The 1,1,2,3 acid is also obtained by the action of barium hydroxide on dlcyancyclopropane 1,2,3 trlcarboxylate. ... 

According to H. N. Stokes, and A. Mente, there are two monimidodiphosphoric acids, differently constituted, but not isomeric—one is dibasic, and the other tetrabasic. H. N. Stokes1 prepared the tetrabasic monimidodiphosphoric acid... 

Tetrabasic monimidodiphosphoric acid, Dibasic monimidodiphosphoric acid,... 

According to A. Rosenheim and J. Pinsker, the f.p. of aq. soln. of hypophosphoric acid and its salts resemble those of pyrophosphoric acid and. its salts, and correspond with the formula H4P20a but it has been argued that this molecular weight really represents associated mols. (H2P03)2 and not the mol. H4P2Oa of a tetrabasic acid. 

The heats of neutralization of pyrophosphoric acid with sodium hydroxide show that the acid is probably tetrabasic, for H. Giran found that the first two displaceable hydrogen atoms have strongly marked acidic functions, and the other two have feeble acidic functions. The graphic formula (HO)2=PO.O.PO=(OH)2 is in agreement with the tetrabasicity of the acid, and with the work of W. A. Tilden and R. E. Barnett. 0. Favel also found pyrophosphoric acid behaved like a tetrabasic acid towards soluble blue indicator. The confident assumption that the phosphorus is quinquevalent precludes H. Wichelhaus formula (H0)2P.0.0.0.P(0H)2 but, before the formula (H0)2P0.0.P0(0H)2 can be definitely accepted, it must be shown that the formulae... 

Curiously enough, tetrabasic pyrophosphoric acid readily forms quaternary or normal pyrophosphates, say Na4P207, etc. and the secondary pyrophosphates, say Na2H2P207, but not the primary and tertiary salts. There is even some doubt if the ternary salt, Na3HP207, and the primary salt, NaH3P207, have been prepared. T. Salzer reported the former in 1894 and H. Giran, the latter in 1903. Abortive attempts have been made to prepare a pair of isomeric potassium sodium pyrophosphates ... 

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