Cooling alternating

To obtain the free acid, dissolve the potassium salt in 50 ml. of cold water, filter the solution if a small undissolved residue remains, and then boil the clear solution gently whilst dilute sulphuric acid is added until the separation of the acid is complete. Cool the solution and filter off the pale orange-coloured crystals of the benzilic acid wash the crystals on the filter with some hot distilled water, drain well, and then dry in a desiccator. Yield of crude acid, 4 g. Recrystallise from benzene (about 50 ml.) to which a small quantity of animal charcoal has been added, filtering the boiling solution through a preheated funnel fitted w ith a fluted filter-paper, as the benzilic acid readily crystallises as the solution cools alternatively, recrystallise from much hot water. The benzilic acid is obtained as colourless crystals, m.p. 150°. 

In addition to volume changes the effect of temperature is also important. Thus the specific latent heat of vaporization of a chemical is the quantity of heat, expressed as kJ/kg, required to change unit mass of liquid to vapour with no associated change in temperature. This heat is absorbed on vaporization so tliat residual liquid or tlie sunoundings cool. Alternatively an equivalent amount of heat must be removed to bring about condensation. Thus the temperature above a liquefied gas is reduced as tlie liquid evaporates and tlie bulk liquid cools. There may be consequences for heat transfer media and the strength of construction materials at low temperatures. 

Freezing Point Temperature at which crystals start to form as a liquid is slowly cooled alternatively, the temperature at which a solid substance begins to melt as it is slowly heated. 

After cooling, 400 ml of sodium-distilled benzene are added, followed by 6Sg of powdered, dry (105-120°G for two hours) lead (II) chloride in one portion. The mixture is then stirred and refluxed for 8 hours and cooled. Alternatively, the lead (II) chloride may be added to the... 

Often it is possible to use a mixture of miscible solvents where the substance to be recrystallised is soluble in one of the solvents but relatively insoluble in the other. The solute can be dissolved hot in a suitable solvent mixture, which is then allowed to cool. Alternatively, the solute can be dissolved in the solvent in which it is more soluble either at elevated or at room temperature the other solvent is then added until crystallisation just begins, and the resulting mixture is cooled to further induce recrystallisation. 

In a modified melt-dispersion method, sulfamethoxazole particles were dispersed in heated water, and powdered beeswax was added. The molten wax droplets collected the drug particles, and spherical agglomerates with sustained-release properties were obtained after cooling. Alternatively, the agglomerates could also be formed at room temperature by using solutions of the wax in a water-immiscible solvent. ... 

Benzoylphenol (4-hydroxybenzophenone) [1137-42-4] M 198.2, m 133.4-134.8 , pK 7.95. Dissolve p-benzoylphenol in hot EtOH (charcoal), filter and cool. Alternatively, crystallise it once from Et0H/H20 and twice from benzene [Gmnwald J Am Chem Soc 73 4934 1951, Dryland Sheppard J Chem Soc Perkin Trans 1 125 1986. [Beilstein 8 IV 1263.]... 

Bitumen (asphalt) is used as a binder in road construction and in protective coatings and adhesives used in the construction industry (4, 5). In the most common processes, the bitumen is heated to 100-200°C until fluid enough to mix with aggregate. The hot-mixed materials must themselves be stored, transported and used hot to maintain their workability. The final strength of a roadway is developed as the mixture cools. Alternatively, the bitumen is diluted with petroleum solvents such as kerosene until fluid, with the final strength of the... 

Shrink fit n. A method of joining circular and annular parts in which the outer member, having a slightly smaller inside diameter than the inner member s outside diameter, is heated, causing it to expand, then slipped into place over the inner member and allowed to cool. Alternatively, one can chill the inner member in liquid nitrogen, slip it into the outer member, and let is warm. Care must be taken in designing the joint to have the final stresses in both members well below yield values so as not to lose the joint to creep over time. Compare snap fit. 

Chloric and bromic acids exist only in aqueous solution, but iodic acid can be isolated in the free state by dissolving I2O5 in a minimum amount of hot water. White crystals of iodic acid precipitate out on cooling. Alternatively, an aqueous suspension of iodine may be oxidized electrolyti-cally, or with concentrated nitric acid, hydrogen peroxide, or ozone. 

Heating and cooling alternately within about +50°C of the Ai line of Figure 11.11. 

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