Magnesium ammonium phosphate

The presence of sparingly soluble components in human urine, such as calcium oxalate, calcium phosphate, magnesium ammonium phosphate, uric acid and l-cystine. Kidney stones are composed mainly of these compounds. 

The most important of the phosphate bonded cements are the zinc phosphate, dental silicate and magnesium ammonium phosphate cements. The first two are used in dentistry and the last as a building material. Copper(II) oxide forms a good cement, but it is of minor practical value. In addition, certain phosphate cements have been suggested for use as controlled release agents. The various phosphate cements are described in more detail in the remainder of this chapter. 

Figure 6.8 Scanning electron micrographs of magnesium ammonium phosphate mortar III (Abdelrazig, Sharp El-Jazairi, 1989) (a) after 1 hour, low magnification, (b) after 1 hour, high magnification showing needle-like and cuboid crystallites.

For a precipitate used in gravimetric analysis magnesium ammonium phosphate has a rather high solubility (0.1 g dm 3 in water at 20°C). Hence solution volumes should be kept as low as possible and the precipitate must be filtered from cold solution. Furthermore, the solution composition must be carefully controlled to ensure the maintenance of conditions of... 

Write a balanced dissolution equation and solubility product expression for magnesium ammonium phosphate, MgNH4P04. 

Magnesium, formerly determined by precipitation as magnesium ammonium phosphate and determining P in the latter, can be analyzed readily by EDTA titrations. It can be obtained either as the difference between titrations for (Ca and Mg) and Ca alone or by titrating the supernatant after Ca is precipitated as oxalate (White and Davies 1962). 

Magnesium Ammonium Phosphate. MgNH(POr. white precipitate. K,t, 2.5 x 0 1 -. by reaction of soluble salt solution and sodium phosphate in the presence of excess ammonium hydroxide, upon igniting yields magnesium pyrophosphate. MgyPsOz. while solid. 

Self-Test 11.13B The solubility product of magnesium ammonium phosphate, MgNH4P04, is 2.5 X 10 l3. Estimate the molar solubility of the salt, which forms Mg24", NH41, and P043- ions in water. 

INFRARED AND RAMAN SPECTRA OF MAGNESIUM AMMONIUM PHOSPHATE HEXAHYDRATE (STRUVITE) AND ITS ISOMORPHOUS ANALOGUES... 

Magnesium nitrate reagent or magnesia mixture White crystalline precipitate of magnesium ammonium phosphate soluble in acetic acid and mineral acids practically insoluble in 2.5% ammonia solution... 

If the water is first concentrated to one-fiftieth of its bulk, tests may be carried out for magnesia and phosphates. The former is precipitated as magnesium ammonium phosphate on standing for some twenty-four hours after addition of sodium phosphate solution to the water rendered alkaline with ammonium hydroxide in the presence of chloride. It is assumed that any lime has previously been removed with ammonium oxalate. Phosphates are precipitated as yellow phosphomolybdate on adding excess of ammonium molybdate solution to the water acidified with nitric acid, and warming. 

Phosphorus combined in organic compounds, or as phosphide in metals, is also estimated after oxidation by precipitation as ammonium phosphomolybdate or magnesium ammonium phosphate, with the subsequent treatment which is described on pp. 181—183. The methods by which the phosphorus is brought into solution vary with the nature of the material which is being analysed. Organic compounds are oxidised in a sealed tube with fuming nitric acid or in a flask by a mixture of concentrated sulphuric and nitric acids. 

Occasionally, phosphates can form undesirable crystals in foods. The most common example is struvite, a magnesium-ammonium phosphate of the composition Mg(NH4)P04-6H20. Struvite crystals are easily mistaken by consumers for broken pieces of glass. Most reports of struvite formation have been related to canned seafood, but occasionally the presence of struvite in other foods has been reported. It is assumed that in canned seafood, the struvite is formed from the magnesium of sea water and ammo-... 

Prepare the other (unhydrolyzed) set of duplicate samples of the magnesium ammonium phosphate supernatant fluid from step 4 by bringing their volumes to 3.0 ml with H 0. That is, set up tubes 5 through 8, which contain 0.05, 0.1, 0.2, and 0.5 ml of the supernatant fluid, respectively. Add2.95,2.9,2.8, and 2.5 ml of H20, respectively to tubes 5 through 8. 

Calculate the number of micromoles of Pi and 7-min phosphate in the entire volume of filtered solution. If the inorganic phosphate (in the unhydrolyzed sample) in the filtrate is less than 15% of the phosphate found after 7-min hydrolysis, you may proceed with the rest of the experiment. (NOTE When students are working in pairs, some instructors prefer to have one student proceed directly with steps 12 through 14 while the other student conducts the assays of steps 5 through 9. This assumes that the magnesium ammonium phosphate precipitation effectively removes most of the inorganic phosphate from your preparation, as occurs in most (but not all) cases. Consult your instructor.)... 

Disodium hydrogen phosphate solution white crystalline precipitate of magnesium ammonium phosphate Mg(NH4)P04.6H20 in the presence of ammonium chloride (to prevent precipitation of magnesium hydroxide) and ammonia solutions ... 

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