Vacuum cooling

Ammonia, hydrochloric acid, and sodium perchlorate are mixed and the reaction mixture crystallised in a vacuum-cooled crystalliser. Ammonium perchlorate crystals are centrifuged, reslurried, recentrifuged, and then dried and blended for shipment. Mother Hquor is evaporated to precipitate sodium chloride and the depleted mother Hquor is recycled to the reactor. The AP product made by this method is 99% pure and meets the specifications for propeUant-grade ammonium perchlorate. The impurities are ammonium chloride, sodium perchlorate, ammonium chlorate, and water insolubles. 

Solution crystalli tion (adiabatic evaporation (vacuum cooling))... 

The cmde oxide is pressure-leached in a steam-heated autoclave using water or circulating mother hquor. The arsenic trioxide dissolves, leaving behind a residue containing a high concentration of heavy metal impurities and sihca. The solution is vacuum-cooled and the crystallisation is controUed so that a coarse oxide is obtained which is removed by centrifuging. The mother hquor is recycled. The oxide (at least 99% purity) is dried and packaged in a closed system. 

Fused under vacuum, cooled, then washed with... 

Decker, L. O., Consider the Cold Facts About Steam-Jet Vacuum Cooling, Chem. Eng. Prog., American Institute of Chemical Engineers, V. 89, No. 1, p. 74 (1993). All rights reserved. 

Alternatively, mixture of 4 g (V), 36 ml benzene, 1.6 g Na carbonate and 7 ml benzoyl-Cl stir and heat 96-100° for ten hours. Evaporate in vacuum, cool to 0° and add 40 ml ice water. Acidify with HCI to pH 5 and extract with 3X20 ml ether. Neutralize the aqueous solution with 20% NH4OH to separate an oil from which cocaine precipitates on standing (from JGC 30,3228(1960)). 

Wedge solidification technique Molten metal is forced into a wedge-shaped metal mould by a vacuum (cooling rate is about 5 104oC/s). 

The temperature-solubility relationship for solute and solvent is of prime importance in the selection of a crystalliser and, for solutions that yield appreciable amounts of crystals on cooling, either a simple cooling or a vacuum cooling unit is appropriate. An evaporating crystalliser would be used for solutions that change little in composition on cooling and... 

Li, H. P., Tajkarimi, M., and Osbum, B. I. (2008). Impact of vacuum cooling on Escherichia coli 0157 H7 infiltration into lettuce tissue. Appl. Environ. Microbiol. 74, 3138-3142. 

Zinc (metal) [7440-66-6] M 65.4, m 420°, d 7.141. Fused under vacuum, cooled, then washed with acid to remove the oxide. 

Freezing. Ill Vacuum cooling-. The material freezes ilsell by the evaporation of water as it is subjected quickly to high vacuum. (2) Direct contact The material is immersed in a cold liquid or in a slrcatn of cold air or inert gases. (3) indirect ronuift The material is frozen on cold surfaces. 

Estimates show that nanosize drops formed in the plasma fly apart at a velocity of 104 cm/scc, whereas the velocity of expansion of the plasma cloud exceeds 106cm/sec. Accordingly, a microsecond after the laser pulse terminates the expanding plasma moves away from the target and charged nanodrops continue their movement in a vacuum, cool down to solidification, and the resulting nanoparticles finally arrive to the substrate surface. 

Brochure, Vacuum Cooling, Croll-Reynolds, Westfield, NJ, No date. Walas, S.M., Chemical Process Equipment, Butterworths, Boston, MA, 1988. 

A solution of 2.9 g (7.3 mmol) MnBr(CO)5 and 2.9 mL (3.4 g, 8.4 mmol) Sn(SC6H5)(n-C4H<,)3 in 40 mL of THF in a 100-mL round-bottom flask (Nz inlet, reflux condenser) is heated at reflux for 6 hr. The solution is allowed to cool. Solvent volume is reduced to 5 mL in vacuum cooling at -15° causes the orange crystalline product to precipitate from solution. This species is separated by filtration and air dried, yield 1.7 g, 93%. Recrystallization can be carried out using hexane. 

Brochure, Vacuum Cooling, Croll-Reynolds, Westfield, NJ, No date. 

Chemistry of the crystalline chloro-trisodium orthophosphate is elucidated. This widely used cleaning and sanitation ingredient can be produced by a melt crystallization approach. A hot phosphatesolution with a Na/P mole ratio of about 2.8 is mixed with a hypochlorite solution. The resulting solution is vacuum cooled to produce crystalline product with a size distribution of about -20+200 mesh, suitable for formulating into automatic dish washing compounds. 

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