Snow crystals crystallization

Figure 2.1. Various forms exhibited by crystals, (a) Polyhedral crystals (b) hopper crystal (c) dendritic crystal (snow crystal, photographed by the late T. Kobayashi) (d) step pattern observed on a hematite crystal (0001) face (e) internal texture of a single crystal (diamond-cut stone, X-ray topograph taken by T.Yasuda) (f) synthetic single crystal boule. Si grown by the Czochralski method (g) synthetic corundum grown by the Verneuil method.

Most of the final product producing recipes in this book will provide for the chemist to take up the final free base product in DCM. Usually the freebase oil in the DCM is dark. Used to be that Someone-Who-ls-Not-Strike (SWINS) would have to distill the freebase to get clear yellow oil before crystallizing because when SWINS used ether or ethanol as a crystallization solvent, the colored crap would contaminate the final product. But not with DCM. Even with the grungiest (well...not too grungy) freebase, the crystals that come out are pure snow. The DCM so strongly solvates the contaminants that none remain in the mass of crystalled final product. The filter cake is sooooo clean even in the darkest solvent ... 

Cloud Seeding. In 1947, it was demonstrated that silver iodide could initiate ice crystal formation because, in the [ -crystalline form, it is isomorphic with ice crystals. As a result, cloud seeding with silver iodide has been used in weather modifications attempts such as increases and decreases in precipitation (rain or snow) and the dissipation of fog. Optimum conditions for cloud seeding are present when precipitation is possible but the nuclei for the crystalliza tion of water are lacking. 

The filtrate and the washings contain in solution a small quantity of the product. This is recovered by distillation with steam. The acid distillate will consist of snow-white crystals (if it is protected from light) and a solution of the compound. The solid is removed by filtration and washed. The filtrate is made neutral with sodium carbonate and extracted with ether. Upon drying and evaporating the ethereal layer will yield mononitrothiophene contaminated with dinitrothiophene (Note 5),... 

If the nitration is caiiied out in accordance with this outline, the product will be crystalline and pale yellow in color. The color is due to traces of dinitrothiophene and the other impurities. Mononitrothiophene has been crystallized by earlier workers from ether, alcohol, benzene, and other solvents. As a rule these solvents fail to yield a snow-white product. It has been found in this work that petroleum ether (b.p. 20-40 ) possesses decided advantages in that by prolonged refluxing it extracts mononitrothiophene but does not readily dissolve the impurities. With petroleum ether, snow-white crystals have been obtained in needles 10 to 20 cm. in length. 

It occurs in brilliant snow-white crystals, m.p. 305° (dec.) and is readily soluble in water or aqueous alcohol. The benzoyl derivative, m.p, 209°. is crystalline and on methylation gives a-coeaine, a base crystallising in prisms, m.p. 87°, and yielding an aurichloride, m.p. 222° (dec.), crystallising in leaflets. It is bitter to the taste but has no local anjesthetic action. 

Baker and Smith have isolated an alcohol of the formula C,oH,gO from the cajuput oil, distilled from the leaves of Melaleuca uncinata. The alcohol, which is probably an open-chain compound, forms snow-white crystals, melting at 72 5°, and having a specific rotation + Sfi fifi . 

When the aldehyde is heated on the water-bath with 25 per cent, hydrochloric acid, it yields a triphenylmethane derivative, nonamethoxy-triphenylmethane, a body consisting of snow-white crystals, melting at 184 5°. The action of concentrated nitric acid upon the solution in glacial acetic acid of this triphenylmethane derivative gives rise to 1, 2, 5-trimethoxy-4-nitrobenzene (melting at 130°). With bromine, nonamethoxytriphenylmethane combines, with separation of a molecule of trimethoxy bromobenzene, into a tribromo additive compound of hexamethoxy diphenylmethane, a deep violet-blue body. The 1, 2, 5-tri-methoxy-4-bromobenzene (melting at 54 5°) may be obtained more readily from asaronic acid. 

The crude product is dissolved in five times its weight of water, and after clearing with a little Norite the solution is diluted with one and one-half volumes of 95 per cent alcohol. The product separates in well-formed, snow-white crystals, and after standing for several days in an ice chest is collected with suction on a Buchner funnel. The yield of purified histidine monohydrochloride is 75-80 g. (Note 5). The compound melts at 251-2520, with decomposition. The amino acid is not race-mized by the procedure employed, and shows the characteristic optical activity, [a]n6° = +8.00, in the presence of three moles of... 

Snow crystals [4] Their macroscopic structure is different from a bulk three-dimensional ice crystal, but they are formed by homologous pair-pair interaction between water molecules and are static and in thermodynamic equilibrium. It should be noted, however, that dendritic crystal growth is a common phenomenon for metals [5-7] and polymers. The crystals grow under non-equilibrium conditions, but the final crystal is static. 

Snow is normally defined as precipitation formed of ice crystals and ice as solid water with hexagonal structure and density about 920 kg m-3. In snow storage the main issue is to have enough amounts of frozen water at low cost why the only relevant distinction is the density. If natural snow or ice is too expensive or not available in enough quantity, it is possible to produce frozen water. Artificial snow and ice made with different types of water sprayers, including snow blowers (snow guns). The production rate depends on equipment, relative air humidity, and temperatures of the air and water. 

The dried product is then recrystallized from 30-35 ml. of a 1 3 mixture of boiling benzene and carbon tetrachloride (Note 7). The yield of snow-white crystals is 15-15.7 g. (82-86%) the recrystallized product melts at 131-132° and is sufficiently pure for synthetic purposes. A second recrystallization gives a product which melts at 132-133° (Notes 8 and 9). 

At the end of the heating period the contents of the flask will have solidified. To the cold mixture 40 ml. of water is added to hydrolyze the potassium methoxide and precipitate the pyrimidine the fine crystals are filtered and dried. The crude product is placed in a 500-ml. distilling flask with 250 ml. of purified kerosene (Note 3). On distilling the kerosene, the pyrimidine codistils and solidifies in the receiving flask to a snow-white mass of crystals. These are filtered, washed well with petroleum ether, and dried in an oven at 100°. The yield of pure material, melting at 182-183°, is 27.5-28.7 g. (67-70%) (Note 4). 

The 2-chlorolepidine is extracted, using two 750-ml. portions of ether (Note 1). The extract is shaken with two 200-ml. portions of water and then dried over 50 g. of potassium carbonate. After removal of the ether, the residual oil is distilled from a 200-ml. modified Claisen flask.2 The colorless distillate boils at 132-135°/3 mm. and weighs 118-122 g. (89-92%). The distillate is melted if necessary and poured into 250 ml. of petroleum ether (b.p. 40-50°) the solution is then chilled in a freezing mixture the crystals are filtered by suction and dried in a vacuum desiccator over paraffin. The snow-white 2-chlorolepidine melts at 58-59° and weighs 114-118 g. (86-89%). 

The interplay of these two basic rates determines the size of the resulting particles. For instance, the reason that snow flakes reach sizes of several cm at lower latitudes but arrive as extremely small crystals, called diamond dust in Antarctica, is that the nuclei that are formed in a cloud, will grow during their voyage to earth by adsorbing water molecules. Obviously, this growth will be more important in the moist atmosphere at low latitudes than in the extremely dry atmosphere above Antarctica. The same interplay of nucleation and growth determine the size of metal particles that are formed on a support by chemical reduction of adsorbed precursors, such as metal ions. Here... 

Atmospheric trace gas chemistry is a new rapidly growing field of paleo-atmospheric research, because the radiative properties of CO2, CH4, and N2O make them potential indicators of climate change. A fundamental problem in constructing a record of trace gas concentrations from ice-cores is the fact that the air in bubbles is always younger than the age of the surrounding ice. This is because as snow is buried by later snowfalls and slowly becomes transformed to fim and ice, the air between the snow crystals remains in contact with the atmosphere until the air bubbles become sealed at the fim/ice transition, when density increases to about 0.83gcm. The trapped air is thus younger than the matrix, with the age difference... 

The distilled dlamide Is a pale yellow oil at room temperature It freezes in the refrigerator (+4 C) If seeded within some hours. The first spontaneous crystallization took several weeks. It can also be obtained as snow white crystals from diisopropyl ether/hexane, rap 15-16°C. 

Crystals are often associated with their unique polyhedral shapes. Their smooth, shining facets provide a constant source of fascination to ancient, arid modem beings alike. Advances in microscopy have not, tainted the myth a bit interesting surface stmctures are found down to the atomic level, be it surface reconstmction, surface ripples and dimples, or snow-flakish fractals... 

The Atomizing Freeze Crystallization (AFC)-Snowfluent technology is specifically designed for cold climates. The technology combines freeze crystallization and snow-making techniques... 

This is because pure acetic acid freezes at 17°C, which is slightly below room temperature. When bottles of pure acetic acid froze in cold labs, snow-like crystals formed on the bottles the term glacial was thus associated with the pure form. Butyric acid comes from the Latin word butyrum for butter butyric acid is responsible for the smell of rancid butter. 

Are you ready for the answer Here is the list of terms sorted in order of beauty as determined by my little survey of scientists and colleagues. The numbers in parentheses indicate the number of times the term was an individual s first choice dancing flames (31), snow crystal (20), mist-covered swamp (17), spiral nautilus shell (10), mossy cavern (5), kaleidoscope image (5), avalanche (4), computer chip (3), seagull s cry (3), tears on a little girl (3), trilobite fossil (2), glimmer of mercury (2), wine (2), asphalt (1). 

Brad P. comments, Both the compnter chip and snow crystal are beantifnl because of their complexity, order and diversity—all within a small package. Both say volumes about the beauty and intelligence of their creators. ... 

If each cage region were to contain a single snow crystal, what size lattice would you need to hold the number of snow crystals necessary to form the ice age, which has been estimated to be 10 ° crystals If you were to draw... 

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