Crystals obtained by cooling

Crystals Obtained by Cooling. Crystallizations in which cooling was the mode of supersaturation were obtained from solutions near the isoelectric point of L-Ile. Such crystals are of zwitterionic form and are referred to as neutral. They are structurally different from the crystals obtained by acid addition because they are free of HCl and do not have a water of hydration. It is not surprising then that different behavior may be observed. 

The benzene crystals obtained by cooling are washed by the liquid resulting from their subsequent pardal fusion, and are thus purified of the impurities which wet them. The composition of the non aromadc compounds present in the feedstock determines the riiape of the crystallization curve ((tmteccic temperature and comporition) and, ac> oordingiy, the operating conditions. 

This may be prepared from concentrated potassium hydroxide solution and Brg in a manner similar to that previously described for NaBrO-SHgO. One mixes 465 g. (300 ml.) of 53% potassium hydroxide solution (245 g. of KOH and 220 g. of HgO) and 314 g. (100 ml.) of Brg. This solution (about 250 ml.) is filtered from precipitated KBr (at this point the solution contains about 70 g. of KBrO per 100 ml.), and 125 g. of KOH and 157 g. (50 ml.) of Br are added with stirring. The temperature is —5 to —10°C. The precipitated KBr is again filtered. The filtrate, which contains about 83 g. of KBrO per 100 ml., is cooled to —40°C and seeded with several crystals obtained by cooling a portion of the filtrate to —80°C. After a short time a substantial yield of long, yellow needles of KBrO 3HgO is obtained. The precipitate is filtered off and dried on a precooled clay plate for about 20 hours in a desiccator at —20°C. 

These solutions are employed in concentrations of 3—15% in various bleaching and sanitising appHcations. Chlorination of 50% caustic and removal of precipitated salt produces a concentrated, low salt solution (32% NaOCl, 6% NaCl), which is used as a process intermediate in Ca(OCl)2 manufacture. Concentrations as high as 45% can be obtained by melting NaOCl 5H20 crystals recovered by cooling this solution. 

The dependence of solubility on temperature affects the mode of crystallization. For example, Figure 4 shows that the solubiUty of potassium nitrate is strongly influenced by the system temperature but that temperature has Httle influence on the solubiUty of sodium chloride. As a consequence, a reasonable yield of KNO crystals can be obtained by cooling a saturated feed solution on the other hand, cooling a saturated sodium chloride solution accomplishes Httle crystallization, and evaporation is required to increase the yield of sodium chloride crystals. 

Desyl chloride (a-cbloro-desoxybenzoin, m-chloro-co-phenyl acetophenone) [447-31-4] M 230.7, m 62-64 , 66-67 ,67.5 , 68 . For the purification of small quantities recrystallise from pet ether (b 40-60°), but use MeOH or EtOH for larger quantities. For the latter solvent, dissolve 12.5g of chloride in 45mL of boiling EtOH (95%), filter and the filtrate yields colourless crystals (7.5g) on cooling. A further crop (0.9g) can be obtained by cooling in an ice-salt bath. It turns brown on exposure to sunlight but it is... 

This oil Is kept supercooled at the ambient temperature. Crystallization may be obtained by cooling or by seeding with crystals of the product. The melting point is 34°C (instantaneous on the Maquenne block). 

Rundle and co-worker performed x-ray diffraction studies on solid phenylmag-nesium bromide dietherate and on ethylmagnesium bromide dietherate, which they obtained by cooling ordinary ethereal Grignard solutions until the solids crystallized. They found that the structures were monomeric ... 

Crystallisation equipment can be classified by the method used to obtain supersaturation of the liquor, and also by the method used to suspend the growing crystals. Supersaturation is obtained by cooling or evaporation. There are four basic types of crystalliser these are described briefly below. 

The distilling flask, collection flask, and column are continuously evacuated with a high-vacuum system. When the bulk of the pentane and residual hexane have distilled away, the temperature of a silicone oil bath surrounding the distillation flask is raised from room temperature to 125° over about a one-hour period. When the distillation rate diminishes appreciably, the temperature is slowly raised to 150° and maintained there until no more liquid is obtained. The distillation flask is cooled to room temperature before air is admitted to the system. The distilled product weighs 86.5 g. (89% yield checkers report 89 %t) and melts at 32 to 32.5°. In this state of purity, (bromomethyl)-carborane is suitable for most uses, but it may be further purified by crystallization from pentane or methanol. For example, crystals obtained by chilling a solution of 86.5 g. of the car-... 

Small solid particles obtained by cooling of vapors, by grinding, or many other methods, usually have a less perfect lattice and more impurity than have bigger crystals of nominally identical composition. Hence, the cuticular energy of the former exceeds that of the latter. 

What is the theoretical yield of crystals which may be obtained by cooling a solution containing 1000 kg of sodium sulphate (molecular mass = 142 kg/kmol) in 5000 kg water to 283 K The solubility of sodium sulphate at 283 K is 9 kg anhydrous salt/100 kg water and the deposited crystals will consist of the deca-hydrate (molecular mass = 322 kg/kmol). It may be assumed that 2 per cent of the water will be lost by evaporation during cooling. 

Therefore a few physical properties of qulzalofop-ethyl such as Its solubility and Its supersolublllty In ethyl alcohol were studied. Two types of crystals with different shapes were obtained by cooling crystallization and the stabilities of the crystals were tested In saturated solutions at various temperatures. 

Two different types of crystals were obtained by cooling crystallization of qulzalofop-ethyl dissolved In ethyl alcohol at room temperature. As shown In Photograph 1, one type consists of plate-llke crystal of 20-50 jum In size and another one Is halrllke crystal of 1-2 pm In short axis size. As shown In Figure 1, different X-ray patterns were obtained for the two crystals. Melting points and heats of fusion were also measured for the two crystal types by DTA and DSC, which are listed In Table I. These results Indicate that the different shapes of the two crystal types are related to differences In crystal lattice. 

B. o-Methylbenzyl alcohol. A solution of 5 g. (0.12 mole) of sodium hydroxide in 50 ml. of water is added to a solution of 16.4 g. (0.1 mole) of 2-methylbenzyl acetate (prepared as described above, part A) in 50 ml. of methanol contained in a 250-ml. round-bottomed flask fitted with a reflux condenser. The mixture is boiled under reflux for 2 hours, cooled, diluted with 50 ml. of water, and extracted with three 75-ml. portions of ether. The combined ether solutions are washed with 50 ml. of water and 50 ml. of saturated sodium chloride solution and dried over anhydrous sodium sulfate. The solvent is removed by distillation, finally at reduced pressure to remove the last traces of methyl alcohol, and the residue is dissolved in 50 ml. of boiling 30-60° petroleum ether. The colorless crystals obtained on cooling, finally in the ice bath, are collected by suction filtration, washed with a few milliliters of cold petroleum ether, and air-dried. Concentration of the mother liquors to 6-7 ml. and cooling gives an additional crop. The total yield of product melting between 33-34° and 35-36° is 11.6-11.8 g. (95-97%) (Note 7). 

Cadmium Arsenides.—The freezing point, density and atomic volume curves indicate the existence of two arsenides, Cd3As2and CdAs2.n The freezing point curve was obtained by cooling mixtures of the elements melted under fused alkali chloride no mixed crystals were observed. Two other arsenides have been described Cd6As, said to... 

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