Water magnesium nitrate

The Ternary System Nitric Acid-Water-Magnesium Nitrate... 

Nantokite, see Copper(I) chloride Natron, see Sodium carbonate Naumannite, see Silver selenide Neutral verdigris, see Copper(H) acetate Nitre (niter), see Potassium nitrate Nitric oxide, see Nitrogen(II) oxide Nitrobarite, see Barium nitrate Nitromagnesite, see Magnesium nitrate 6-water Nitroprusside, see Sodium pentacyanonitrosylfer-rate(II) 2-water... 

Thermo dynamic data for nitric acid are given ia Table 2. Properties for the ternary systems sulfuric acid—nitric acid—water (5,14) and magnesium nitrate—nitric acid—water (11,15—17) used ia processes for concentrating nitric acid are available. 

Nitric acid-water Maximum-hoiling azeotrope Sulfuric acid, magnesium nitrate for salt process Sulfuric acid process relies heavily on boundary curvature... 

A solution is made up by adding 0.925 g of silver(I) nitrate and 6.25 g of magnesium nitrate to enough water to make 375 mL of solution. Solid sodium carbonate is added without changing the volume of the solution. 

The four samples from each location were (1) nonfiltered, nonstabilized water for alkalinity testing, (2) field-filtered, nonstabilized water for nitrate and chloride testing, (3) field-filtered water stabilized with nitric acid for calcium, magnesium, and sodium testing, and (4) field-filtered water stabilized with sulfuric acid for ammonia and phosphate testing. 

Procedure (determination of inorganic phosphate (a) in the acetic acid extract). The 8-hydroxyquinoline forms a precipitate in acidic ammonium molybdate solution, which will interfere unless the aliquot is <5 ml. It should therefore be removed by ignition as follows. Transfer 10 ml acetic acid extract to a 45-ml silica basin, add 0.5 ml 1 M magnesium acetate and evaporate to dryness on a water-bath. (Note do not use magnesium nitrate, which reacts adversely on heating with 8-hydroxyquinoline.)... 

The monazite sand is heated with sulfuric acid at about 120 to 170°C. An exothermic reaction ensues raising the temperature to above 200°C. Samarium and other rare earths are converted to their water-soluble sulfates. The residue is extracted with water and the solution is treated with sodium pyrophosphate to precipitate thorium. After removing thorium, the solution is treated with sodium sulfate to precipitate rare earths as their double sulfates, that is, rare earth sulfates-sodium sulfate. The double sulfates are heated with sodium hydroxide to convert them into rare earth hydroxides. The hydroxides are treated with hydrochloric or nitric acid to solubihze all rare earths except cerium. The insoluble cerium(IV) hydroxide is filtered. Lanthanum and other rare earths are then separated by fractional crystallization after converting them to double salts with ammonium or magnesium nitrate. The samarium—europium fraction is converted to acetates and reduced with sodium amalgam to low valence states. The reduced metals are extracted with dilute acid. As mentioned above, this fractional crystallization process is very tedious, time-consuming, and currently rare earths are separated by relatively easier methods based on ion exchange and solvent extraction. 

C.G. Wade, USP 3715247(1973) CA 78, 126471(1973) [Water-in-oil emulsion expl containing entrapped gas. An example is AN 31-7, NaN03 10, Ediylenediamine Dinitrate 10, NH4CI04 10, magnesium nitrate hexahydrate 12.3 and water 20 (heated until all dissolved), blended with a mixture of Indra 2119 wax 2 and sorbitan monooleate 10 parts, followed by addition of Corcel hollow glass agglomerates to make 100 parts]... 

The control solution is prepared as follows Take 10 mL of a solution of magnesium nitrate hexahydrate in ethanol (95) (1 in 10), and fire the ethanol to bum. Cool, add 1 mL of sulfuric acid, heat carefully, and ignite between 500 and 600°C. Cool and add 3 mL of hydrochloric acid. Proceed as directed in the test solution, then add the volume of standard lead solution directed in the monograph and water to make 50 mL. 

A different method for lowering the melting point of ammonium nitrate was suggested a few years before World War II. It consists of the addition of hydrated magnesium nitrate (i.e. containing water of crystallization) Mg(N03)2.6H20 to... 

Magnesium Nitrate may be detd by a gravimetric method, weighing Mg PgOf as the final product or by titrating an aliquot of the water extract with EDTA (Ethylenediamine-tetracetic Acid) at a pH of ca 10 using Eriochrome Black T indicator. This method is described in Ref 17, D90-5d, pi5... 

Magnesium nitrate (6H2O) [13446-18-9] M 256.4. Crystd from water (2.5ml/g) by partial evapn in a desiccator. 

For a continuous extractive distillation process to be possible there must be adequate enhancement of the nitric acid-water relative volatility, and a system equilibrium which permits virtually complete separation of nitric acid from magnesium nitrate, the latter taking up the water content of the weak acid feedstock. This requires addition to the weak nitric acid of solutions of magnesium nitrate usually containing 60 wt% or more of Mg(NC>3)2. Under these conditions a nitric acid-water relative volatility of greater than 2.0 is obtained at the low end of the liquid phase concentration at a nitric acid mole fraction below 0.05 (4, 7). 

Figure 1. Magnesium nitrate-water solubility diagram...

Aqueous solutions of magnesium nitrate are appreciably denser and more viscous than water. Table II illustrates data (9) On the densities (in g/ml) of concentrated solutions at high temperatures. Figure 2 illustrates the viscosity variations in concentrated solutions (9). 

The hydration of anhydrous magnesium nitrate evolves heat, 25,730 cal/g mole Mg(NC>3)2 — Mg(NC>3)2 6H2O (II). Likewise, the dissolution of Mg(NC>3)2 or the hydrates in water or the addition of further water to these solutions also evolves heat (12,13,14,15). Figure 4 illustrates the molar integral heat of solution of Mg(NC>3)2, the value for infinite dilution being 21,575 cal/g mole. From these figures, the enthalpies of magnesium nitrate solutions may be computed. 

Figure 5. Magnesium nitrate-nitric acid-water equilibrium vapor composition...

Since in an extractive distillation process based on this ternary system the extractive agent is nonvolatile and remains in the liquid phase, and since because of the similarity of the molar latent heats of nitric acid and water there is substantially constant molar liquid overflow, the mole fraction of magnesium nitrate remains almost constant throughout the process. It is appropriate to represent the equilibrium situation as a pseudo-binary system for each magnesium nitrate concentration, and Figure 7 shows vapor-liquid equilibria on a nitric acid-water basis at a series of magnesium nitrate concentrations from zero to 0.25 mole fraction in the liquid phase. 

Thermal data for the ternary system have not been widely reported, but may be evaluated as required for process calculations from available data for the nitric acid-water and magnesium nitrate-water binary systems. 

Figure 7. System magnesium nitrate-nitric acid-water, liquid-vapor equilibrium, pseudo binary basis...

Heat Requirement of the Process. Heat is required for vaporization in the extractive distillation column, and for the reconcentration of magnesium nitrate solution. Overall thermal effects caused by the magnesium nitrate cancel out, and the heat demand for the complete process depends on the amount of water being removed, the reflux ratio employed, and the terminal (condenser) conditions in distillation and evaporation. The composition and temperature of the mixed feed to the still influence the relative heat demands of the evaporation and distillation sections. For the concentration of 60 wt% HNO3 to 99.5 wt% HNO3 using a still reflux ratio of 3 1, a still pressure of 760 mm Hg, and an evaporator pressure of 100 mm Hg, the theoretical overall heat requirement is 1,034 kcal/kg HNO3. 

Weak nitric acid (normally 60 wt% HNO3) and concentrated magnesium nitrate solution (72 wt% Mg(NC>3)2) enter at the feed point of an extractive distillation column. The rectifying section above the feed point has a water-cooled... 

In 1957 Hercules Inc. started the first unit that produced concentrated nitric acid for commercial sales using magnesium nitrate as the extractive agent. In this process (see Figure 2) the weak nitric acid product from an AOP is fed to the appropriate tray of a distillation column. A concentrated solution of magnesium nitrate and water is fed to the proper tray in sufficient quantity to enrich the vapors to a concentration greater than 68 wt % nitric acid. The overhead product from the column is concentrated (98-99.5 wt %) nitric acid. A portion of the concentrated nitric acid is returned as reflux to aid in rectification. The... 

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