Metal-POSS

The effects of metal-containing POSS on the combustion behavior of polypropylene have been investigated.46 Metal-POSS was prepared from incompletely condensed structures by reaction with organometallic compounds. The dimeric and oligomeric of Al and Zn-isobutyl silsesquiox-ane (POSS) have been evaluated as potential flame retardants for polypropylene, and the results were compared with PP/octaisobutyl POSS. The cone calorimeter data (Table 8.2) revealed that... 

Fig. 286. Preparation of metallic rare earths by reduction of the chloride with metallic po-tassiiun. a rare earth chloride h, fo metallic potassium c filling tube for the rare earth chloride d connection to vacuum pump.

The parameter Po/ o in sq. (10) is a measure of the purity of a material. For very pure metals Po/ Ao = 0. Figure 4 shows, e.g., dependences L/Lq = f T/0) calculated using eq. (10) for a number of values of Po/4Aq. A decrease of L compared to Lq is connected with the inelastic character of electron scattering by phonons in this temperature region. At very low temperatures in metals with impurities and for T> 0 electrons are scattered elastically (Smirnov and Tamarchenko 1977). In some metals (e.g., monovalent and noble ones) for T>0 one finds that Linelastic scattering mechanism - electron-electron scattering (Smirnov and Tamarchenko 1977). In the thermal conductivity theory any deviation of L from Lq indicates the presence of some new elastic or inelastic scattering mechanism for the current carriers. 

In dilute acids NH30H reduces Te compounds to Te. Selenium and tellurium can be separated, however, by precipitating the Se from 5-M HCl with NHsOH", leaving the Te dissolved. Metallic Po is formed from Po02-aq suspended in dilute OH, plusN2H4orNH20H. 

Metallic Po precipitates from PoOz-aq in dilute Off plus [8204] ". 

Polonium (Po) is a radioactive element that was discovered in 1898 by Marie Sklodowska-Curie and Pierre Curie. Po is used in brushes to remove dust from photographic films and to avoid charge static accumulation produced by several processes, such as the rolling of paper, wire, and sheet metal. In addition, Po has been alloyed with beryllium to be used as a neutron source. All these and other applications depend on Po s structural properties. Po is the only element of the periodic table that adopts the simple cubic (sc) structure at ambient pressure (a few other elements such as Ca-III and As-II present the sc, but only at high pressure [1]), and this structure has a low atomic packing factor and is rare in nature. The first experimental studies of Po s crystal structure, by using electron diffraction, were reported in 1936 by Rollier et al. [2]. Several years later, Beamer and Maxwell [3,4] and Sando and Lange [5] reported on their X-ray diffraction experiments on metallic Po. From these reports, we know that Po exhibits two structural phases the a phase (a-Po), which has the sc structure p Pmim)], a = 3.345(2) A [4], and the /3 phase (/3-Po), stable above 77(9)°C, which has the rhombohedral (r) structure [Df (/ 3m)], a = 3.359(1) A, and a = 98.22(5)°. 

U, - meaning of linear relaxation coefficient for i - element tomogram s, Vi - volume of object, appropriate i -clement tomogram s, po - meaning of linear relaxation coefficient of a matrix material, (p/p)mei - mass relaxation coefficient of metal, wo - faaor of a pore filling material... 

Orthophosphate Hquid mixtures are ineffective as micronuttient carriers because of the formation of metal ammonium phosphates such as ZnNH PO. However, micronutrients are much more soluble in ammonium phosphate solutions in which a substantial proportion of the phosphoms is polyphosphate. The greater solubiHty results from the sequestering action of the polyphosphate. The amounts of Zn, Mn, Cu, and Fe soluble in base solution with 70% of its P as polyphosphate are 10 to 60 times their solubiHties in ammonium orthophosphate solution. When a mixture of several micronutrients is added to the same solution, the solubiHty of the individual metals is lowered significantly. In such mixtures the total micronuttient content should not exceed 3% and the storage time before precipitates appear may be much shorter than when only one micronuttient is present. 

Monofluorophosphates. Monofluorophosphates are probably the best characterized series of fluoroxy salts. The PO F ion is stable ia neutral or slightly alkaline solution. The alkaU metal and ammonium monofluorophosphates are soluble ia water but the alkaline-earth salts are only slightly soluble, eg, CaPO F is not water-soluble and precipitates as the dihydrate. 

Uses. The principal use of monosodium phosphate is as a water-soluble soHd acid and pH buffer, primarily in acid-type cleaners. The double salt, NaH2P04 H PO, referred to as hemisodium orthophosphate or sodium hemiphosphate, is often generated in situ from monosodium phosphate and phosphoric acid in these types of formulations. Mixtures of mono- and disodium phosphates are used in textile processing, food manufacture, and other industries to control pH at 4—9. Monosodium phosphate is also used in boiler-water treatment, as a precipitant for polyvalent metal ions, and as an animal-feed supplement. 

Hydroxyapatite, Ca2Q(PO (OH)2, may be regarded as the parent member of a whole series of stmcturaHy related calcium phosphates that can be represented by the formula M2q(ZO X2, where M is a metal or H O" Z is P, As, Si, Ga, S, or Cr and X is OH, F, Cl, Br, 1/2 CO, etc. The apatite compounds all exhibit the same type of hexagonal crystal stmcture. Included are a series of naturally occurring minerals, synthetic salts, and precipitated hydroxyapatites. Highly substituted apatites such as FrancoHte, Ca2Q(PO (C02) (F,0H)2, are the principal component of phosphate rock used for the production of both wet-process and furnace-process phosphoric acid. 

The tertiary metal phosphates are of the general formula MPO where M is B, Al, Ga, Fe, Mn, etc. The metal—oxygen bonds of these materials have considerable covalent character. The anhydrous salts are continuous three-dimensional networks analogous to the various polymorphic forms of siHca. Of limited commercial interest are the alurninum, boron, and iron phosphates. Boron phosphate [13308-51 -5] BPO, is produced by heating the reaction product of boric acid and phosphoric acid or by a dding H BO to H PO at room temperature, foUowed by crystallization from a solution containing >48% P205- Boron phosphate has limited use as a catalyst support, in ceramics, and in refractories. 

The metal dissolves readily in concentrated HCl, H PO, HI, or HCIO. Nitric acid (qv) forms a protective oxide skin on the metal and can be removed by ca 0.05 Af HF. Dissolution of Pu metal in HNO —HF mixtures is common practice in scrap-recovery plants. The metal does not dissolve readily in H2SO4 because passivation of the metal surface occurs. The reaction of water and Pu metal is slow compared to that in HCl, HI, or HCIO. ... 

Most mineral acids react vigorously with thorium metal. Aqueous HCl attacks thorium metal, but dissolution is not complete. From 12 to 25% of the metal typically remains undissolved. A small amount of fluoride or fluorosiUcate is often used to assist in complete dissolution. Nitric acid passivates the surface of thorium metal, but small amounts of fluoride or fluorosiUcate assists in complete dissolution. Dilute HF, HNO, or H2SO4, or concentrated HCIO4 and H PO, slowly dissolve thorium metal, accompanied by constant hydrogen gas evolution. Thorium metal does not dissolve in alkaline hydroxide solutions. 

Trisodium phosphate [7601-54-9] trisodium orthophosphate, Na PO, is an important constituent of hard-surface cleaners including those for ceramic, metal, or painted surfaces. It may be used with soaps, surfactants, or other alkaHes. It precipitates many heavy-metal ions but does not sequester to form soluble chelates. It is thus a precipitant builder and additionally an alkaH. 

Authors are designed row sensitive and selective test-systems for analysis of heavy metals, active chlorine, phenols, nitrates, nitrites, phosphate etc. for analysis of objects of an environment and for control of ions Ee contents in the technological solutions of KH PO, as well as for testing some of pharmacological psychotropic daigs alkaloids (including opiates), cannabis as well as pharmaceutical preparations of phenothiazines, barbiturates and 1,4-benzodiazepines series too. 

It will be recalled that is 100% abundant and is the heaviest stable nuclide of any element (p. 550), but it is essential to use very high purity Bi to prevent unwanted nuclear side-reactions which would contaminate the product Po in particular Sc, Ag, As, Sb and Te must be <0.1 ppm and Fe <10ppm. Polonium can be obtained directly in milligram amounts by fractional vacuum distillation from the metallic bismuth. Alternatively, it can be deposited spontaneously by electrochemical replacement onto the surface of a less electropositive metal... 

Polonium is unique in being the only element known to crystallize in the simple cubic form (6 nearest neighbours at 335 pm). This a-form distorts at about 36° to a simple rhombohedral modification in which each Po also has 6 nearest neighbours at 335 pm. The precise temperature of the phase change is difficult to determine because of the self-heating of crystalline Po (p. 751) and it appears that both modifications can coexist from about 18° to 54°. Both are silvery-white metallic crystals with substantially higher electrical conductivity than Te. 

Several atomic and physical properties of the elements are given in Table 16.2. The trends to larger size, lower ionization energy and lower electronegativity are as expected. The trend to metallic conductivity is also noteworthy indeed, Po resembles its horizontal neighbours Bi, Pb and T1 not only in this but in its moderately high density and notably low mp and bp. 

Pseudohalides of Se in which the role of halogen is played by cyanide, thiocyanate or selenocyanate are known and, in the case of Se are much more stable with respect to disproportionation than are the halides themselves. Examples are Se(CN)2, Se2(CN)2, Se(SeCN)2, Se(SCN)2, Se2(SCN)2. The selenocyanate ion SeCN is ambidentate like the thiocyanate ion, etc., p. 325), being capable of ligating to metal centres via either N or Se, as in the osmium(IV) complexes [OsCl5(NCSe)], [OsCl5(SeCN)], and trans-[OsCU(NCSe)(SeCN)]2-.920) Tellurium and polonium pseudohalogen analogues include Te(CN)2 and Po(CN)4 but have been much... 

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