Prismatic crystals

Properties.—Usually in tufts of capillary crystals prismatic orthodiagonal. H. = 1-1-5. G. =4 5-4-6. Lustre adamantine. Colour cherry-red. Streak brownish red. Feebly translucent. 

Properties.—Orthorhombic crystals prismatic, often acutely terminated vertical planes striated or deeply furrowed longitudinally crystals often curved, bent in knee-shaped forms or twisted. Commonly occurs in confused aggregates of acicular crystals, also in radiating groups massive, coarse or fine, columnar. H. = 2. G. = 4-52-4-62. Lustre metallic, highly splendent. Colour and streak lead-gray. 

C), the yield of more than 90% purity L-glutamic acid crystals is very high. The glutamic acid crystals appear as both the metastable a- and stable P-forms. The a-form consists of prismatic crystals which are easy to filter, whereas the P-form needle crystals are difficult to filter. Control of crystallisation conditions of a-crystals are requited (13). The cmde L-glutamic acid crystals are suspended ia water and neutralized with caustic soda or sodium hydroxide. The solution is decolorized with activated carbon to produce a transparent solution and MSG is crystallized under reduced pressure. 

Below 65°C, sodium iodide is present ia aqueous solutions as hydrates containing varyiag amounts of water. When anhydrous sodium iodide is dissolved ia water, heat is Hberated because of hydrate formation, eg, AH = —174.4 kJ/mol (—41.7 kcal/mol), when the dihydrate is formed. At room temperature, sodium iodide crystallizes from water as the dihydrate [13517-06-1/, NaI-2H2 02H2O, ia the form of colorless prismatic crystals. 

Cyclosporin A forms white prismatic crystals from acetone and is only slightly soluble in water and saturated hydrocarbons, but is very soluble in methanol, ethanol, acetone, and diethyl ether. Optical and nmr data on cyclosporins and x-ray crystallographic data on cyclosporin A and an io do derivative have been reviewed (273,275). 

Pure biphenyl is a white crystalline soHd that separates from solvents as plates or monoclinic prismatic crystals. Commercial samples are often slightly yellow or tan in color. Similady, pure terphenyls are white crystalline soHds whereas commercial grades are somewhat yellow or tan. Physical and chemical constants for biphenyl and the three isomeric terphenyls are given in Tables 2 and 3, respectively. 

Crystal growth modifiers have been employed to improve filterabiHty and water retention of Ca(OCl)2 2H20, which typically crystallizes as fine plates. Addition of zinc dust or salts produces larger square- and diamond-shaped, untwinned dihydrate crystals (215). Coarse prismatic crystals are obtained by use of carbohydrates and carboxyHc acids and thek salts (216). 

Oscine, CgHiaOjN, This substance, for which the name scopolin is in use in continental Europe, was first examined by Hesse and later t Luboldt. It forms colourless, hygroscopic prismatic crystals, m.p. 109 from ether or light petroleum, and boils at 241-3°. cZZ-Oscine has bee resolved into the d- and Z-forms by King by crystallisation of tl d-hydrogen tartrates. The characters of the three forms of oscine and ( their picrates and hydrochlorides are tabulated on p. 87. 

It is a solid body melting at 112° to 114°, forming exceedingly fine prismatic crystals. It forms a compound with phthalic acid, melting at 140°. 

There was obtained a mixture of N-(2 -diethylamino-2 -methylethyl)phenthiazine and N-(2 -diethylamino-1 -methylethyDphenthiazine in the form of a viscous yellow oil, BP 202° to 205°C/2 mm. This oil was treated in ethereal solution with ethereal hydrogen chloride and gave a white solid which was fractionally crystallized from ethylene dichloride. The less soluble fraction, N-(2 -diethylamino-2 -methylethyl)phenthiazine hydrochloride formed colorless rhombs, MP 223° to 225°C. The more soluble N-(2 -diethylamino-1 -methylethyl)-phenthiazine hydrochloride was obtained as colorless prismatic needles, MP 166° to 168°C. 

Preparation of 2-Hydroxy-4,4 -Dicyanostilbene 10 grams of 2-amino-4,4 -dicyanostilbene thus prepared were dissolved in 400 cc of boiling glacial acetic acid and 200 cc of dilute sulfuric acid added the solution was suddenly chilled and diazotized over one and a half hours at 5° to 10°C with sodium nitrate (3.0 grams/15 cc H O). The diazonium salt solution was decomposed by boiling for 15 minutes with 600 cc of 55% aqueous sulfuric acid solution the solution was diluted, cooled and filtered. The residue crystallized from ethyl alcohol as lemon yellow prismatic needles, MP 296°C. 

Preparation of 3-Amino-5-Methylisox3Zo/e 1.7 grams of ethyl 5-methylisoxa2ole-3-car-bamate was heated on a boiling water-bath with 5 cc of a 10% aqueous sodium hydroxide solution for 8 hours, then the reaction mixture was extracted several times with ether or benzene and the extract was cooled followed by the removal of the solvent and drying. The residue was solidified after a while and gave prismatic crystals, melting point 61° to 62°C, of 3-amino-5-methylisoxazole by recrystallization from benzene. 

A similar distortion may occur in some crystals with the wurtzite structure. Wurtzite and greenockite show easy prismatic cleavage and difficult basal cleavage, whereas iodyrite, Agl, cleaves perfectly on the... 

One of the intensively discussed topics was the question about the shape of atoms - a question with also high educational relevance, if we think of some students preconceptions. We can focus on two main positions One group of chemists observed that crystals always broke to parts with similar shapes to those of the original crystal. Therefore, their theory was that the smallest particles of atoms must have also the same shape as the macroscopic crystal. If we follow Domenico Guglielmini (1655-1710), the particles of sodium chloride would be cubic, those of calcspar would be triclinic. Hexagonal-prismatic and trigonal-prismatic crystals... 

Crystals usually appeared within 4 days and grew to a maximum length of 0.7 mm within 10 days. The crystals were dark red in color with a prismatic habit. 

Mechanical adhesion. Cracks and pits are produced on the treated rubber surface which favor the mechanical interlocking with the adhesive. Eurthermore, unreacted solid prismatic TCI crystals on the treated rubber surface can be dissolved by the organic solvent into the adhesive, favoring the reaction with the adhesive. 

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