Potassium nitrate, crystallization solubility

The solubility diagrams of several species are shown in Fig. 2, and these illustrate the importance of solubility behavior in the selection of the mode of crystallization. For example, consider the differences between potassium nitrate and sodium chloride The solubility of potassium nitrate is strongly influenced by the system temperature, whereas the opposite is true for sodium chloride. As a consequence, (1) a high yield of potassium nitrate crystals can be obtained by cooling a saturated feed solution,... 

When the aqueous solutions of two water-soluble compounds are mixed, there may be a reaction between the ions of these solutions. If one of the products is insoluble, crystals of this product fall from the resulting solution. This solid product is called a precipitate. Let us consider the reaction between the solutions of lead(ll) nitrate, Pb(N03)2, and potassium iodide, Kl. According to the solubility table in Appendix A, both are soluble in water. This means that the solution of lead(ll) nitrate contains Pb2+ and N03 ions, and the potassium iodide solution contains K+ and I- ions. The possible products of this reaction are Pbl2 and KN03. According to solubility rules, potassium nitrate is soluble in water, but lead(ll) iodide is not. As soon as the two reactants mix, insoluble lead(ll) iodide crystals settle at the bottom of the container as a yellow precipitate. 

The anticaking properties of acid magenta and other dyestuffs have been described by Whetstone, who recommends an 0.10% coverage of ammonium nitrate crystals during the crystallization process from solution as the preferred method. Butchart claims the addition of certain water-soluble anthraquinone derivatives to solutions or to wet crystals to promote free-flowing low setting tendencies in potassium nitrate crystals. Similar improvements are claimed by Marti for the addition of 2-3 % CuO or CuaO to ammonium nitrate. 

Sodium chloride is less soluble than KCl, NaNOs and KNO3. It separates out by crystallization. The remaining solution is cooled to ambient temperature. Potassium nitrate crystaUizes out. 

Crystallization is facilitated by the great difference in solubility of potassium nitrate at high and low temperatures (it is ten times more soluble at 100°C than at 10°C). 

The tables of solubility show that at 20° about 32 g. of potassium nitrate dissolves in 100 g. of water while at 100° about 246 g. dissolves (Fig. 1). From a hot, saturated solution the salt deposits too rapidly to give good crystals, for the rate of radiation depends upon the difference between the temperature of the solution and that of the room. Modify the procedure of Exercise 1 as follows ... 

Nitrate, Potassium nitrate, [CAS 7757-79-1], saltpeter, niter, KNO3. white solid, soluble, mp 333°C, formed by fractional crystallization of sodium nitrate and potassium chloride solutions. Used Cl) in matches, explosives, pyrotechnics, (2) in the pickling of meat. (3) in glass, (4) in medicines, (5) as a rocket-fuel oxidizer, and (6) in the heal treatment of steel. See also Fertilizer. 

For example, suppose that sodium nitrate and potassium chloride in equivalent amounts are added to 100 grams of water at 10°, so that the total weight of K+ and N03 radicals will be 42 grams the potassium nitrate in excess of its solubility will then crystallize out, and 21 grams of the crystals will thus be obtained. The presence of the radicals of sodium chloride in the solution is without effect on the potassium nitrate. 

Lead Cobalti-cyanide, Pb3[Co(CN)6]2.4H20, is prepared by the action of hydrogen cobalti-cyanide upon lead carbonate.1 It yields laminated crystals, soluble in about three parts of water. The salt is not precipitated by adding potassium cobalti-cyanide to a solution of either lead acetate or nitrate. 

Silver chromate is almost insoluble in water, glacial acetic acid, and in solutions of potassium chromate, but soluble in those of ammonia, caustic alkalies, nitrates, and in dilute acetic acid. A concentrated solution of ammonium nitrate is a good crystallising medium for silver chromate. With chlorine, above 200° C., silver chloride, chromium trioxide, and oxygen are produced. The solution in ammonia contains the compound Ag2Cr04.4NH3, which forms crystals isomorphous with the corresponding ammoniacal sulphate. ... 

Due to a very low solubility of its potassium salt, hexyl is used as a reagent for potassium. Also a suggestion was made for using hexyl to extract potassium from sea water [92]. The precipitated potassium salt treated with nitric acid yielded potassium nitrate which on evaporation crystallized out. 

Commercial crystallizers may operate either continuously or batchwise. Except for special applications, continuous operation is preferred. The first requirement of any crystallizer is to create a supersaturated solution, because crystallization cannot occur without supersaturation. Three methods are used to produce supersaturation, depending primarily on the nature of the solubility curve of the solute. (1) Solutes like potassium nitrate and sodium sulfite are much less soluble at low temperatures than at high temperatures, so supersaturation can be produced simply by cooling. (2) When the solubility is almost independent of temperature, as with common salt, or diminishes as the temperature is raised, supersaturation is developed by evaporation. (3) In intermediate cases a combination of evaporation and cooling is effective. Sodium nitrate, for example, may be satisfactorily crystallized by cooling without evaporation, evaporation without cooling, or a combination of cooling and evaporation. 

Solubility op Mixed Crystals of Potassium Nitrate and Silver Nitrate in Water at 25°. 

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