Glass crystallisation

Ding, Y. et al. (1995) Second order optical non-linearity of surface crystallised glass with lithium niobate, J. Appl. Phys., 77, 2208-10. 

Abrahams, I. and Hadzifejzovic, E., Lithium ion conductivity and thermal behaviour of glasses and crystallised glasses in the system Li20-Al203-Ti02-P205, Solid State Ionics, 134, 249, 2000. 

Keywords. Poly(e-caprolactone), Blend, Phase behaviour. Crystallisation, Glass-transition temperature. Properties... 

The etching time required to remove a partially crystallised glass structure with a given thickness decreases with increasing HF concentration. Therefore, commonly a 10% HF solution is used because of the notably shorter etching times. 

Sometimes the crude substance may contain an insoluble impurity, and on cooling the solution it may be difficult to judge how much of the solid matter is merely undissolved impurity and how much is solute which has subsequently crystallised from solution. To avoid this difficulty, the hot solution should be filtered, and should thus always be absolutely clear before cooling is attempted. Therefore filter the hot solution into a clean tube through a very small fluted filter-paper contained in a correspondingly small glass funnel, which should have had its stem cut off as that shown in Fig. 6, p. 12 (and for the same reason). Unless the upper part of the filter is cut awav to reduce its size to a minimum, a large proportion of the solution will remain held mechanically in the pores of the paper itself and only a few drops of clear filtrate will be obtained. 

The hot filtered solution is then without delay poured into a lipped beaker or a conical flask not into an evaporating-basin, since it is crystallisation and not evaporation which is now required), the beaker covered with a watch-glass, and then cooled in ice-water. As cooling proceeds, the solution should be stirred from time to time to facilitate crystallisation, and when crystallisation appears complete, the cooling should be continued for at least another 15 minutes. 

CrystaUisation and Filtration. Crystallisation is carried out in apparatus of conventional type but reduced in size. Glass rods should... 

Lead formate separates from aqueous solution without water of crystallisation. It can therefore be used for the preparation of anhydrous formic acid. For this purpose, the powdered lead formate is placed in the inner tube of an ordinary jacketed cond ser, and there held loosely in position by plugs of glass-wool. The condenser is then clamped in an oblique position and the lower end fitted into a receiver closed with a calcium chloride tube. A current of dry hydrogen sulphide is passed down the inner tube of the condenser, whilst steam is passed through the jacket. The formic acid which is liberated... 

If difficulty is experienced in inducing the first crude crop of the a-glucoside to ciystallise, place a few drops of the solution on a watch glass and expose freely to the air, with occasional scratching meanwhile keep the main volume of the solution securely corked in the conical flask. After an interval of varying length (possibly several days), partial crystallisation occurs in the material on the watch-glass. Then seed the solution with this material crystallisation of the first main crop will rapidly follow. 

For alcohols of b.p. below 150°, mix 0- 5 g. of 3-nitrophthalic anhydride (Section VII,19) and 0-5 ml. (0-4 g.) of the dry alcohol in a test-tube fitted with a short condenser, and heat under reflux for 10 minutes after the mixture liquefies. For alcohols boiling above 150°, use the same quantities of reactants, add 5 ml. of dry toluene, heat under reflux until all the anhydride has dissolved and then for 20 minutes more remove the toluene under reduced pressure (suction with water pump). The reaction product usually solidifies upon cooling, particularly upon rubbing with a glass rod and standing. If it does not crystallise, extract it with dilute sodium bicarbonate solution, wash the extract with ether, and acidify. Recrystallise from hot water, or from 30 to 40 per cent, ethanol or from toluene. It may be noted that the m.p. of 3-nitrophthalic acid is 218°. 

Dissolve 1 g. of the ketomethylene compound and 1 1 g. or 2 2 g. of pure benzaldehyde (according as to whether the compound may be regarded as RCOCHjR or as RCHjCOCHjR ) in about 10 ml. of rectified (or methylated) spirit, add 0 5 ml. of 5.N -sodium hydroxide solution, shake and allow the mixture to stand for about an hour at room temperature. The benzylidene derivative usually crystallises out or will do so upon scratching the walls of the vessel with a glass rod. Filter off the solid, wash it with a little cold alcohol, and recrystallise it from absolute alcohol (or absolute industrial spirit). 

Anhydrous oxalic acid may be prepared by heating the finely-powdered A.R. crystallised acid, spread upon large clock glasses, in an electric oven at 105° for 6 hours, allowing to cool in a desiccator and storing in a tightly stoppered bottle. 

Add 0 -5 ml. of phenyl isothiocyanate to the distillate and shake the mixture vigorously for 3-4 minutes. If no derivative separates, crystallisation may be induced by cooling the flask in ice and scratching the walls with a glass rod. Filter off the crude product, wash it with a little 50 per nent. ethanol, and recrystaUise from hot dilute alcohol. (See Table 111,123 for melting points of phenylthiourea derivatives of amines.)... 

Heat a mixture of hexamethylene dicyaiiide with 15 times its weight of 50 per cent, sulphuric acid by weight under reflux for 10 hours. The acid crystallises out on cooling. Filter oflF the suberic acid upon a sintered glass funnel, and recrystallise it from acetone m.p. 141-142°. The yield is 90 per cent, of the theoretical. 

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