Crystallization of water

Ci2Hi2Br2N2. Yellow crystals m.p. 335-340°C, containing water of crystallization soluble in water. Made from 2,2 -dipyridyl and... 

Water of crystallation (solid state spectra) 3600-3100 (w) Usually a weak band at 1640-1615 cm also. Water in trace amounts in KBr disks shows a broad band at 3450 cm k... 

Lead borate moaohydrate [14720-53-7] (lead metaborate), Pb(B02)2 H20, mol wt 310.82, d = 5.6g/cm (anhydrous) is a white crystalline powder. The metaborate loses water of crystallization at 160°C and melts at 500°C. It is iasoluble ia water and alkaHes, but readily soluble ia nitric and hot acetic acid. Lead metaborate may be produced by a fusion of boric acid with lead carbonate or litharge. It also may be formed as a precipitate when a concentrated solution of lead nitrate is mixed with an excess of borax. The oxides of lead and boron are miscible and form clear lead-borate glasses in the range of 21 to 73 mol % PbO. 

Lithium Acetate. Lithium acetate [546-89 ] is obtained from reaction of lithium carbonate or lithium hydroxide and acetic acid. Crystalline lithium acetate dihydrate [6108-1 7a(/, CH2C02Li 2H20, melts congmentiy in its own water of crystallization at 57.8°C. The anhydrous salt [646-89-4] melts... 

Flame and Smoke Retardants. Molybdenum compounds are used extensively as flame retardants (qv) (93,94) in the formulation of halogenated polymers such as PVC, polyolefins, and other plastics elastomers and fabrics. An incentive for the use of molybdenum oxide and other molybdenum smoke and flame retardants is the elimination of the use of arsenic trioxide. Although hydrated inorganics are often used as flame retardants, and thought to work by releasing water of crystallization, anhydrous molybdenum oxides are effective. Presumably the molybdenum oxides rapidly form... 

Nickel acetate tetrahydrate [6018-89-9] Ni(C2H202) 4H2O, is a green powder which has an acetic acid odor, density 1.74 g/cm. When heated, it loses its water of crystallization and then decomposes to form nickel oxide. Nickel acetate is used as a catalyst intermediate, as an intermediate in the formation of other nickel compounds, as a dye mordant, as a sealer for anodized aluminum, and in nickel electroplating (59). 

Aluminum Sulfate (Alum). Alum, a double sulfate of potassium and aluminum having twelve waters of crystallization, KA1(S0 2 12H20, is the earliest referenced aluminum containing compound. It was mentioned by Herodotus in the fifth century BC. The Egyptians used alum as a mordant and as a medicine the Romans used it for fireproofing. Some alums contain sodium or ammonium ions in place of potassium. 

Amino-4-nitrophenol. This derivative, 2-hydroxy-5-nitroani1ine (9), forms orange prisms from water. These prisms are hydrated with one water of crystallization, mp 80—90°C, and can be dehydrated over sulfuric acid to the anhydrous form, mp 143 —145°C. The compound is soluble in ethanol, diethyl ether, acetic acid, and warm benzene and slightly soluble in water. 

Barium nitrite [13465-94-6] Ba(N02)2, crystallines from aqueous solution as barium nitrite monohydrate [7787-38-4], Ba(N02)2 H2O, which has yellowish hexagonal crystals, sp gr 3.173, solubihty 54.8 g Ba(NO2)2/100 g H2O at 0°C, 319 g at 100°C. The monohydrate loses its water of crystallization at 116°C. Anhydrous barium nitrite, sp gr 3.234, melts at 267°C and decomposes at 270 °C into BaO, NO, and N2. Barium nitrite may be prepared by crystallization from a solution of equivalent quantities of barium chloride and sodium nitrite, by thermal decomposition of barium nitrate in an atmosphere of NO, or by treating barium hydroxide or barium carbonate with the gaseous oxidiation products of ammonia. It has been used in diazotization reactions. 

Drying is an operation in which volatile Hquids are separated by vaporization from soHds, slurries, and solutions to yield soHd products. In dehydration, vegetable and animal materials are dried to less than their natural moisture contents, or water of crystallization is removed from hydrates. In freeze drying (lyophilization), wet material is cooled to freeze the Hquid vaporization occurs by sublimation. Gas drying is the separation of condensable vapors from noncondensable gases by cooling, adsorption (qv), or absorption (qv) (see also Adsorption, gas separation). Evaporation (qv) differs from drying in that feed and product are both pumpable fluids. 

Benzoylene urea is reported to separate from aqueous solution with from one to five molecules of water of crystallization. 

There are many materials containing water of crystallization that simply cannot be dried under ordinary conditions. These materials would loose all or a portion of this water. Under such widely varying conditions drying must be accomplished in a drier that takes into consideration the rate of drying, the condition of the drying medium, and the nature of the exposed surfaces of the material. Each of these factors is complex and requires careful engineering. 

Water of crystallization, aquo complexes and solid hydrates... 

A number of salts have been isolated but, especially those of Sm" and Yb", are susceptible to oxidation even by their own water of crystallization. Carbonates and sulfates, however, have been characterized and shown to be isomorphous with those of Sr" and Ba". 

A mixture of 5.0 g of 3-chloro-5-(3-chloropropyl)-10,11 -dihydro-5H-dibenz(b,f)azepine, 5.0 g of 4-carbamoyl-4-piperidinopiperidine and 50 mi of dimethylformamide is heated at 100°C for 10 hours. The solvent is distilled off. After the addition of a 2% sodium carbonate solution to the flask, the content is scratched to yield a semisolid, which is dissolved in 50 ml of isopropanol. A solution of 5 g of maleic acid in 50 ml of isopropanol is added, and the precipitate is collected by filtration and recrystallized from isopropanol to give 5.6 g of crystalline 3-chloro-5-[3-(4-carbamoyl-4-piperidino-piperidino)propy I] -10,1 l-dihydro-SH-dibenz-Ib.fjazepine dilhydrogen maleate) with 1/2 molecule of water of crystallization melting at 181°C to 183°C. 

The soon crystallizing dihydrochloride is separated by filtration, dried and recrystallized from 120 parts by volume of ethanol. Thus, after drying for 3 days over 8265, 40-50 grams (66-70% of the theoretical) of N,N -bis-[(3,4,5-trimethoxy benzoloxy)propyl] homopiperazine dihydrochloride containing 1 mol of water of crystallization is obtained. This product has a melting point at 194°-19B°C. 

The N,N -dibenzyl-N,N -bis-[2-(3, 4 -dihydroxyphenyl)-2-oxoethyl] -hexamethylene-diamine-dichlorohydrate-monohydrate used as the starting material was prepared as follows 2 mols of chloroaceto pyrocatechin were dissolved in 2,000 cc of acetone and heated to boiling with 2 mols of N,N -dibenzylhexamethylene-diamine for 12 hours, almost the theoretical quantity of N,N -dibenzylhexamethylene-diamine-dichlorohydrate being precipitated and removed by suction after cooling. Excess HCI was added to the filtrate, approximately 66% of the theoretically possible quantity of crude dichlorohydrate of the N,N -dibenzyl-N,N -bis-[2-(3, 4 -dihydroxyphenyl)-2-oxoethyl] -hexamethylene-diamine being precipitated. The product was cleaned by recrystallization from water with the addition of animal charcoal. After drying the substance contained water of crystallization at ambient temperature, MP 206° to 209.5°C. 

Free N,N -bis-[2-(3, 4 -dihydroxyphenyl)-2-hydroxyethyl]-hexamethylene-diamine can be separated from these salts by the addition of the equivalent quantity of caustic alkali solution. It has a melting point of 162° to 165°C and contains half a mol of water of crystallization. 

Pipethanate hydrochloride Is dissolved in water and the solution is made alkaline by adding 10% sodium hydroxide solution. The crystals that are separated are filtered off and recrystallized from dilute ethanol. The monohydrate thereby obtained is dehydrated at 100°C under reduced pressure for 20 minutes. The products that are now in the form of a syrup due to loss of water of crystallization are further dehydrated for 2 days in a desiccator over phosphorus pentoxide whereupon the anhydrous pipethanate is obtained. 

Dianilinoethane, containing water of crystallization, is best dried by melting under vacuum. 

NOTE Filter alum does not always contain 18 molecules of water of crystallization some grades are only 14 to 16 H20. 

Phosphates were proposed as alternatives to carbonate because they did not break down. Various types were employed, including mono-(NaH2-), di- (Na2H-), and trisodium phosphate (NajPO, with or without water of crystallization. 

Dozens of phosphates are commercially available, supplied as anhydrous materials or with varying levels of water of crystallization, although only a limited number are employed for BW precipitating treatment programs. 

Meaning without water and describing salts that do not contain any water of crystallization. 

A variation of this approach has recently been provided by Lyakhov et al. [598] who, from measurements of water adsorption on CuS04 5 H20, on MgS04 7 H20, and on their respective dehydration products, discern a correlation between strengths of surface bonding and S—T behaviour. At low surface coverages, the mutual dipole—dipole repulsions in the adsorbed layer inhibit water loss, in part by a blocking action on loss of water of crystallization and in part by polarization effects which provide a... 

The kinetic behaviour of metal salts of oxyacids may be influenced by water of crystallization. Where complete-dehydration precedes decomposition, the anhydrous material is the product of a previous rate process and may have undergone recrystallization. If water is not effectively removed, there may at higher temperature be the transient formation of a melt prior to decomposition. The usual problems attend the identification of partial or transient liquefaction of the reactant in the mechanistic interpretation of kinetic data. 

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