Flakes crystallization

Physical Description A brief summarization of the form of a substance, specifying whether it is solid, powder, flakes, crystals, liquid, gas, etc., accompanied by identification of color and odor where applicable. 

Grade Powdered, flake, crystals, rods, plates, fibers. 

Particle shape spherical or flake Crystal structure cubic... 

Raw materials. A material balance is always needed to determine the amount of raw materials and their costs. The quality grade and the form of the raw material (powder, flake, crystal, or liquid) affect the cost. Quantity discounts on large contract amounts... 

Formula we ht 116.83. Colorless, birefrii ent, hygroscopic flakes, crystallizing in rhombic form, which are decomposed by water, releasing nitric oxides. The dry compound does not attack glass. 

Details A solid in flake, crystal or dust form. Used in production of epoxy-phenolic resins, monomer of polycarbonates (PC), an antioxidant for PVC, and as an inhibitor used during PVC polymerisation. PC are widely used in many consumer products, from sunglasses and CD to water and food containers and shatter-resistant baby bottles. Some polymers can also contain bisphenol A, and epoxy resins containing bisphenol A are common coatings used in food cans. 

However, some flakes show the presence of pits growing in the flake whilst others are in the process of disintegrating completely, presumably due to imperfections in the original flake crystal structure, as shown in Figure 25 A and B respectively. It may be noted that the pits are highly erratic and have no clear structure. 

Nanoaerosols are produced fi om all kinds of sources intentionally or as a by-product. Environmental nanoaerosols are produced in the atmosphere by natural nucleation and condensation or incomplete combustion of hydrocarbons. The latter are mostly soot particles between 10 and 100 nm in diameter. Engineered nanoaerosols are a result of recent rapid advances in nanotechnology, produced when manufactured nanomaterials become suspended in the air or other carrier gases. These particles usually have complex shapes, including sphere, cube, cylinder, flake, crystal, etc. These different shapes affect their aerodynamics. 

The precipitate was collected by filtration, washed with water, and dried. Then a solution of the product in 50ml of DMF was dropped to a stirring solution of NaOH (3.2g) and Na2C03 (9.6g) in 2L of water. After stirring for 10 minutes, a little charcoal was added to the solution, filtered, and the filtrate was ajusted to pH 3 again, then the obtained precipitate was collected by filtration, washed with water, and dried. Pale brown flake crystals of were obtained from crystallization in 50 ethyl alcohol. The yield was 57%, and mp 1 85 1 86 0. 

Figure 9.11 gives some examples of snow flake crystals and some gems used in ornaments. 

Carry out this preparation in precisely the same way as the above preparation of oxamide, using 2 ml. (2-4 g.) of benzoyl chloride instead of the ethyl oxalate, and observing the same precautions. Considerably more heat is generated in this reaction therefore hold the cork very securely in position during the shaking. After vigorous shaking for 15 minutes, no trace of oily benzoyl chloride remains. Filter off the fine flakes of benzamide, wash with cold water, and then recrystallise from hot water yield, 1-5 g. Colourless crystals, m.p. 130°. 

Urea processes provide an aqueous solution containing 70—87% urea. This solution can be used directiy for nitrogen-fertilizer suspensions or solutions such as urea—ammonium nitrate solution, which has grown ia popularity recentiy (18). Urea solution can be concentrated by evaporation or crystallization for the preparation of granular compound fertilizers and other products. Concentrated urea is sohdified ia essentially pure form as prills, granules, flakes, or crystals. SoHd urea can be shipped, stored, distributed, and used mote economically than ia solution. Furthermore, ia the soHd form, urea is more stable and biuret formation less likely. 

Manufacture. Anhydrous ammonium bifluoride containing 0.1% H2O and 93% NH4HF2 can be made by dehydrating ammonium fluoride solutions and by thermally decomposing the dry crystals (7). Commercial ammonium bifluoride, which usually contains 1% NH F, is made by gas-phase reaction of one mole of anhydrous ammonia and two moles of anhydrous hydrogen fluoride (8) the melt that forms is flaked on a cooled dmm. The cost of the material in 1992 was 1.48/kg. 

Up to 0.4 g/L of the iodine stays in solution and the rest precipitates as crystallized iodine, which is removed by flotation (qv). This operation does not require a flotation agent, owing to the hydrophobic character of the crystallized element. From the flotation cell a heavy pulp, which is water-washed and submitted to a second flotation step, is obtained. The washed pulp is introduced into a heat exchanger where it is heated under pressure up to 120°C to melt the iodine that flows into a first reactor for decantation. From there the melt flows into a second reactor for sulfuric acid drying. The refined iodine is either flaked or prilled, and packed in 50- and 25-kg plastic-lined fiber dmms. 

The crystallized iodine is decanted and transferred into a fusion kettie. The melted product is contacted with strong sulfuric acid to remove organic impurities and humidity. Finally the iodine is flaked or prilled and packed. 

Naphthalenol. 2-Naphthol or p-naphthol or 2-hydroxynaphthalene/7i3 -/5 -i7 melts at 122°C and boils at 295°C, and forms colorless crystals of characteristic, phenoHc odor which darken on exposure to air or light. 2-Naphthol [135-19-3] is manufactured by fusion of sodium 2-naphthalenesulfonate with sodium hydroxide at ca 325°C, acidification of the drowned fusion mass which is quenched ia water, isolation and water-washing of the 2-naphthalenol, and vacuum distillation and flaking of the product. A continuous process of this type has been patented (69). The high sulfate content ia the primary effluent from 2-naphthol production is greatiy reduced ia modem production plants by the recovery of sodium sulfate. 

Gumylphenol. -Cumylphenol (PGP) or 4-(1-methyl-l-phenylethyl)phenol is produced by the alkylation of phenol with a-methylstyrene under acid catalysis. a-Methylstyrene is a by-product from the production of phenol via the cumene oxidation process. The principal by-products from the production of 4-cumylphenol result from the dimerization and intramolecular alkylation of a-methylstyrene to yield substituted indanes. 4-Cumylphenol [599-64-4] is purified by either fractional distillation or crystallization from a suitable solvent. Purification by crystallization results in the easy separation of the substituted indanes from the product and yields a soHd material which is packaged in plastic or paper bags (20 kg net weight). Purification of 4-cumylphenol by fractional distillation yields a product which is almost totally free of any dicumylphenol. The molten product resulting from purification by distillation can be flaked to yield a soHd form however, the soHd form of 4-cumylphenol sinters severely over time. PGP is best stored and transported as a molten material. 

Graining, flaking, and spraying have all been used to make soHd ammonium nitrate particles. Most plants have adopted various prilling or granulation processes. Crystallized ammonium nitrate has been produced occasionally in small quantities for use in specialty explosives. The Tennessee Valley Authority developed and operated a vacuum crystallization process (25), but the comparatively small crystals were not well received as a fertilizer. 

One commercial process for producing sodium sulfide is as a by-product of barium carbonate production (see Barium compounds). Barite ore, BaSO, is reduced with carbon at 800°C to produce cmde barium sulfide (black ash), which is then leached to dissolve the barium sulfide in solution. The solution is then reduced using sodium carbonate to produce barium carbonate, leaving a weak sodium sulfide solution as the by-product. The sodium sulfide solution may then be concentrated and flaked or crystallized. 

An electrolytic process for purifying cmde vanadium has been developed at the U.S. Bureau of Mines (16). It involves the cathodic deposition of vanadium from an electrolyte consisting of a solution of VCI2 in a fused KCl—LiCl eutectic. The vanadium content of the mixture is 2—5 wt % and the operating temperature of the cell is 650—675°C. Metal crystals or flakes of up to 99.995% purity have been obtained by this method. 

Chromic acid flakes Sodium dichromate Chromic acid crystals... 

Fig. 2. Flow diagram for the production of sodium chromate, sodium dichromate, and chromic acid flake and crystals.

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