Crystalline solids formation

Crystalline-Solid Formation versus Glass Formation... 

How does glass formation differ from crystalline-solid formation ... 

Crystalline solid formation is a slow process that can occur at room temperature.. It can occur through chemical change (see Activity 4.1). It can occur when a supersaturated solution is disturbed. It can also occur when a saturated solution slowly evaporates. 

Students will state observed differences between crystalline-solid formation and glass formation. 

Demonstration 4.1 The Difference Between Crystalline-Solid Formation and Glass Formation... 

CH rCHCH NHCSNH. Colourless crystalline solid with a faint garlic-like odour m.p. 74 C. Manufactured by treating propenyl isothiocyanate with a solution of ammonia in alcohol. It has been given by injection in the treatment of conditions associated with the formation of excessive fibrous tissue. Toxic side reactions may occur. Propenyl thiourea is a chemical sensitizer for photographic silver halide emulsions. 

Crystalline solids at temperatures above absolute zero are never perfeet in that all lattiee sites are oeeupied in a eompletely regular manner. Imperfeetions exist. Formation of sueh sites is endothermie a small quantity of energy is required. Point defeets oeeur, of whieh the prineipal two are a vacant lattiee site, and an interstitial atom that oeeupies a volume between a group of atoms on normal sites that affeets erystal purity (see Hull and Baeon, 2001, for a detailed exposition). 

Treatment of the S.yV-ylide 3 with dimethyl acetylenedicarboxylate yields (amongst other products) the stable 1,2-thiazocine derivative 4 as a colorless crystalline solid, via a [6 + 2]-cycload-dition reaction. The formation of 2-ethyl, 3,4-dimethyl 5,6,7,8-tetrachloro-2//-l,2-thiazocine-2,3,4-tricarboxylate (4) may not necessarily involve a concerted mechanism.2... 

This sequence of formation of radical cation which is followed by a C—S bond scission into alkyl radical and alkyl sulfonyl cation was previously suggested by the same authors for the radiolysis of polyfolefin sulfonefs in the solid state72 and was confirmed by scavenger studies73. Scavengers are ineffective in crystalline solids such as dialkyl sulfones and hence could not be used in this study. 

Primary aromatic amides are crystalline solids with definite melting points. Upon boiling with 10-20 per cent, sodium or potassium hydroxide solution, they are hydrolysed with the evolution of ammonia (vapour turns red litmus paper blue and mercurous nitrate paper black) and the formation of the alkali metal salt of the acid ... 

Dining preparation by dissolving the metal in 72% perchloric acid, the hexahydrate separates as a crystalline solid. After filtration, the damp crystals must not contact any organic material (filter paper, horn spatula, or recrystallisation solvent) as the adherent perchloric acid is above 72% concentration owing to the hexahydrate formation [1,2],... 

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