Lead Orthophosphates

Lead orthophosphate, Pb3(P04)2, is a white insoluble compound, which, like lead apatite, Pbio(P04)g(OH)2, can be reduced by hydrogen at comparatively low temperatures (4.7). Lead orthophosphate is one of the least soluble lead salts (Table 5.22) and the least soluble orthophosphates (Table 5.12). It exists as monoclinic a-Pb3(P04)2, rhombohedral 3-Pb3(P04)2, or as an apatite-type structure, Pb9(P04)g(0H)2 (Table 5.20). Also known are Pbio(P04)gO, Pb3(P04)2-Pb0 and Pb3(P04)2-5Pb0. 

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Nriagu, J. O. 1972. Lead orthophosphates. I solubility and hydrolysis of secondary lead orthophosphate. Inorganic Chemistry, 11, 2499-2503. 

Nriagu, J. O. 1973a. Lead orthophosphates. II stability of chloropyromorphite at 25 °C. Geochimica Cosmochimica Acta, 37, 367-377. 

Nebel and Cramer (I40) show that the addition of a series of lead compounds to carbon at a concentration of ca. 5 wt. % lowers the ignition temperature (raises the combustion rate) of the carbon. Of importance is the finding that the extent of the catalytic effect depends on the particular salt. Lead acetate is the most effective, lowering the ignition temperature 293° lead sulfate is the least effective, lowering the ignition temperature only 39°. Lead pyrophosphate and lead orthophosphate are found not to lower the ignition temperature. 

SYNS BLEIPHOSPHAT (GERMAN) C.I. 77622 LEAD ORTHOPHOSPHATE LEAD PHOSPH. TE LEAD PHOSPHATE (3 2) LEAD(2-F) PHOSPHATE NORMAL LEAD ORTHOPHOSPHATE PHOSPHORIC ACID, LEAD(2-l-) SALT (2 3) PLUMBOUS PHOSPHATE TRILEAD PHOSPHATE... 

Guimaraes DMC (1979) Ferroelastic transformations in lead orthophosphate and its structure as a function of temperature. Acta Crystallogr A 35 108-114... 

Nriagu JO (1974) Lead orthophosphate - IV Formation and stability in the environment. Geochim Cosmochim Acta 38 887-898... 

If apatite is treated with lead chloride solution, it forms pyromorphite (Chapter 5). This pyromor-phite (or lead orthophosphate) can then be reduced by hydrogen at comparatively low temperature... 

The use of esters such as tributyl, tricresyl or aesyl diphenyl phosphate results in smoother combustion and improved engine performance when incorporated as petroleum additives. One function of the esters is to combine with lead from lead tetraethyl and expel it as relatively harmless lead orthophosphate. 

We developed a sensor for determination of content of phosphorars in metallurgical melts. In quality of ion conductor used orthophosphate of calcium which pressed in tablets 010 mm. Tablets (mass 1-2 g) annealed at a temperature 400°C during 7-10 h. Tablets melts then in a quartz tube and placed the alloy of iron containing 1 mass % P. Control of sensor lead on Fe - P melts. Information on activities (effective concentration) of phosphorars in Fe - P melts was received. It is set that the isotherm of activity of phosphorars shows negative deviations from the Raouls law. Comparison them with reliable literary inforiuation showed that they agree between itself. Thus, reliable data on activities (effective concentration) of phosphorars in metallic melts it is possible to received by created electrochemical sensor for express determination. 

Likewise, there are at least 10 well-characterized potassium orthophosphates and several ammonium analogues. The presence of extensive H bonding in many of these compounds leads to considerable structural complexity and frequently confers important properties (see later). The... 

They considered that cement formation was the result of an acid-base reaction leading to the formation of hydrates by a through-solution mechanism, by nucleation and precipitation from pore fluids. Two phases were found in the matrix, one amorphous and the other crystalline. The crystalline phase was newberyite. Finch Sharp concluded that the amorphous phase was a hydrated form of aluminium orthophosphate, AIPO4, which almost certainly contained magnesiiun. They ruled out a pure AlP04.nH20, for they considered that the reaction could not be represented by the equation... 

Adsorption inhibitors act by forming a film on the metal surface. The action of traditional oil-based red lead paint formulations presumably involves the formation of soaps and the precipitation of complex ferric salts that reinforce the oxide film. There has been substantial interest in recent years in development of replacements for lead-based and chromate-based inhibitor systems. Adsorption inhibitors based on pol3rmers have been of particular interest. In this volume, Johnson et al. and Eng and Ishida discuss inhibitors for copper 2-undecylimidazole is shown to be effective in acid media, where it suppresses the oxygen reduction reaction almost completely. Polyvlnyllmidazoles are shown to be effective oxidation inhibitors for copper at elevated temperatures. Also in this volume, Chen discusses the use of N-(hydroxyalkyl)acrylamide copolymers in conjunction with phosphate-orthophosphate inhibitor systems for cooling systems. 

Preparative scale reduction of oximes at a mercury or lead cathode in acid solution has been used in the conversion of the carbonyl function to amine. Originally, 30-50% sulphuric acid was used as solvent [195] but ethanol with dilute hydrochloric acid is usually satisfactory. Aliphatic and aromatic oximes give amines in 64-86% yields [196]. Aromatic ketoximes are also reducible in alkaline solution and acetophenone oxime has been converted to 1-phenylethylamine in a tri-potassium orthophosphate solution [197], The reduction of oximes in acid solution is tolerant of many other substituents as indicated by a number of examples [198, 199, 200. Phenylglyoxa monoxime in acid solution is however reduced at both the carbonyl and the oxime centres by sodium amalgam to yield 2-amino-1-phenylethanol [201]... 

Monazite, a rare earth orthophosphate LaCeP04, has in nature the ability to incorporate large amounts of U and Th which leads at some point to the CaXh(P04)2 brabantite phase. It remains crystalhne despite high a-decay doses even in the case of very old crystals (over 2 bilhon years). Cathodolu-minescence allowed estimation of the degree of auto irradiation received by natural monazite (Nasdala et al. 2002). Photoluminescence was used as well on... 

The intermediate stages of the reaction are indicated by the scheme NH(P0C12)2 —>N(P0C12)3, and this product, on hydrolysis, furnishes the acid in question. The free acid cannot be isolated, though lead, barium, and silver salts can be readily obtained. The alkali salts are crystalline and soluble in water. Oxidizing agents convert the soln. into orthophosphates. 

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