Magnesium orthophosphate

Synonyms magnesium orthophosphate, neutral magnesium phosphate, tri-... 

Magnesium orthophosphate Mg3(P04)2 constitutes rhombic crystals melts at 1,184°C insoluble in water soluble in ammonium salt solution. 

A. V. Smirnov, N. E. Suzina, T. V. Kulakovskaya and I. S. Kulaev (2002b). Magnesium orthophosphate, a new form of reserve phosphates in the halophilic archaeon Halobacterium salinarium (in Russian). Mikrobiologiia, 71, 786-793. 

The quantity, -895.10 2.50 kcal mol", is taken as the most probable value for the enthalpy of formation of magnesium orthophosphate. 

This paper reports the synthesis and characterization of various magnesium and sodium-magnesium orthophosphates and their use as catalysts for the dehydration-dehydrogenation of 2-hexanol. 

Consistent with their low surface areas, magnesium orthophosphates contain few acid and basic sites (Table 1). All of them contain more acid sites than basic sites on their surface, as determined by the retention isotherms of cyclohexylamine and phenol, respectively. Only in the solid MgOc the population of basic sites is larger than that of acid sites. 

Aramendia. MA Barrios. J Borau. V Jimenez. C Marinas. JM Romero. FJ Ruiz. JR Urbano. FJ. Selective gas-pha.se dehydrogenation of cyclohexanol with magnesium orthophosphates. Studies in Surface Science and Cittalysis. 1994 82. 769-776. 

Sodium polyphosphate is often used in a concentration of about lO-lOOppm, sometimes with added zinc salts to improve inhibition. The pH value is adjusted to 5-6 in order to minimize pitting and tubercle formation, as well as scale deposition. Polyphosphates decompose slowly into orthophosphates, which, in the presence of calcium or magnesium ions, precipitate insoluble calcium or magnesium orthophosphate, causing scale formation on the warmer parts of the system. Unlike chromates, they favor algae growth, which necessitates the addition of algaecides to the water. Corrosion inhibition with polyphosphates is less effective than that by chromates, but polyphosphates in low concentration are not toxic, and the required optimum amount of inhibitor is less than that for chromates. 

Quick-setting cements based on magnesium orthophosphates have been developed (Chapter 12.10). 

The differences in fertilizer-soil reactions of calcium and magnesium (pyro-) phosphates, respectively, were successfully determined by Raman and synchrotron infrared microspectroscopic studies. All calcium orthophosphates convert to hydroxyapatite in soil over time. On the other hand, magnesium orthophosphates react only as far as trimagnesium phosphate because of then-inability to form an apatite structure. Thus, for the magnesium-based compound, phosphorus remains in a plant-available form. Also, the pyrophosphates of calcium and magnesium react very differently. Calcium pyrophosphate did not react in soil, whereas magnesium pyrophosphate quickly forms dimagnesium phosphate. Furthermore, mineral phases of soils were detectable by infrared microspectroscopy. 

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