Distillation and sublimation

The process of sublimation is the conversion from the solid to the gas phase, without the substance melting. This is possible only for a relatively small proportion of all organic compounds 

List five criteria that should be used in selecting a solvent for recrystallization. 

Prelab Exercise Compare the operation of a barometer, used to measure atmospheric pressure, and a mercury manometer, used to measure the pressure in an evacuated system. 

Many substances cannot be distilled satisfactorily in the ordinary way, either because they boil at such high temperatures that decomposition occurs or because they are sensitive to oxidation. In such cases purification can be accomplished by distillation at diminished pressure. A few of the many pieces of apparatus for vacuum distillation are described on the following pages. Round-bottomed Pyrex ware and thick-walled suction flasks are not liable to collapse, but even so safety glasses should be worn at all times when carrying out this type of distillation. 

Carry out vacuum distillation behind a safety shield. Check apparatus for scratches and cracks 

A typical vacuum distillation apparatus is illustrated in Fig. 1. It is constructed of a round-bottomed flask (often called the pot ) containing the material to be distilled, a Claisen distilling head fitted with a hair-fine capillary mounted through a rubber tubing sleeve, and a thermometer with the bulb extending below the side arm opening. The condenser fits into a vacuum adapter that is connected to the receiver and, via heavy-walled rubber tubing, to a mercury manometer and thence to the trap and water aspirator. 

The capillary is made in three operations. First, a 6-in. length of 6-mm glass tubing is rotated and heated in a small area over a very hot flame to 

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The processes of distillation and sublimation are closely related. There are three ways in which the vaporisation of a thermally stable substance may take place on heating —... 

Camphor Manufacture. Camphor is obtained both naturally and synthetically. Natural camphor is obtained from the wood of the camphor tree, Cinnamormum camphora which grows ia China and Japan. The camphor is isolated by combination of steam distillation, filtration, distillation, and sublimation (169). Natural camphor is the (+)-camphor, whereas synthetic camphor is racemic both products are recognized by the USP. In 1995, the price of synthetic camphor was 7.15/kg (45). In 1992—1993, the total production of synthetic camphor ia India was 3800 t, which is estimated to be about 40% of the world consumption (170). The largest single use (80%) of camphor is for religious purposes ia Asian countries. 

Equally precise and meticulous as an experimentalist, he devoted time during his days at Pittsburgh to write comprehensive articles on such practical techniques as crystallization, vacuum distillation, and sublimation, which were published in the Weissberger Techniques of Organic Chemistry series. His preoccupation with careful experimental techniques and then-accurate recording in the literature remained with him always. He abhorred vague descriptions of procedures, speculative interpretations not based on... 

J.H. Perry, Edit, "Chemical Engineers Handbook , McGraw-Hill, NY (1950), pp 561—660 (Distillation and sublimation)... 

We find in Albertus a general knowledge of many specific facts and operations of chemistry. He knew of the operations of distillation and sublimation and of the apparatus used in these operations, of the purification of gold and silver by cementation and by the use of lead. He knew that quicksilver may be successively distilled without loss of weight that cinnabar can be produced by the union of quicksilver and sulphur that wine, when heated gives off an inflammable substance which he calls an oil (oleum) supernatant and inflammable. 61 He describes many metals, minerals, salts and other substances, without, however, adding any facts of interest not comprised in the authorities which precede him. 

The ninth book is devoted to arts connected with chemistry, as distillation and sublimation, the arts of coining and the manufacture of jewelry, mirrors of metal, etc. In this book appears a description of methods for extracting all gold or silver from the waste of the mines or sweepings of the mint. It is of especial interest because it describes, apparently for the first time, recovery of silver by the method of amalgamation, a process first apparently utilized on a large scale by the Spaniards in America later in that century. He says ... 

The Philosopher expects it when the body, dissolved by a natural Resolution, is submitted to the action of putrefying heat. Distillation and Sublimation have been invented only in imitation of these processes of Nature in regard to the Elements, the inclination or disposition of which to become rarified and to ascend, and to become condensed and to descend, causes all the mixtures and productions of Nature. 

Distillation and Sublimation, philosophically speaking, are a cleansing, subtlization, rectification of matter. 

Bulky CH-alcohols can readily be synthesized according to standard organic procedures and are easily purified by distillation and sublimation, respectively (Scheme 4) [23-26]. 

Chapter 7 Vacuum Distillation and Sublimation TABLE 3 Sublimation Unknowns... 

In this Spiritu mercurii is lodged a subtile oil, the red volatile Gold of the Philosophers, the volatile Fire of Nature, which we extract as well, out of our Central-Salt through moderate distillation and sublimation. 

Macromolecules, submitted). Four isomeric acetonaphthols and 2,4-diaceto-l-naphthol were synthesized by known reactions (27), as simmarized in Scheme I. Purification of these compounds was achieved by a combination of recrystallization, distillation and sublimation, and took advantage of the large differences in boiling point and solubility between intramolecularly H-bonded isomers such as l-aceto-2-naphthol and intermolecul arly H-bonded isomers such as 4-aceto-l-naphthol. The methacrylate esters were synthesized by reaction with methacryloyl chloride in CHgCl y at 0-20°C in the presence of 1 equivalent of pyridine. The monomers are crystalline solids and their structures were verified by IR, NMR and elemental analysis. 

So perhaps someday some chemist will discover a peculiar component in an odd new ore or in a meteoric fragment from a dying star. Then fires will be stoked and vats will bubble. Chemists will bend over beakers with acids and oils to dissolve, digest, distill, and sublime. . . ... 

Dioscorides, in his De Materia Medica, discussed the components of perfumes and their medici nal properties, providing detailed perfume formulae. Alexandrian chemists were divided into three schools, one of which was the school of Maria the Jewess, which produced pieces of apparatus for distillation and sublimation, such as the bain-marie, useful for extracting the aromatic oils from plant material. Perfumes became more commonly known in medieval Europe as knights returning from the Crusades brought back musk, oral waters, and a variety of spices. 

Geoffroy had not included any component dealing with heat in his 1718 affinity theory. Nevertheless, it had long been appreciated that heat affected chemical combination indeed, the traditional agent of the chemist was fire. Nicknames like philosophers by fire , sooty empirics , even puffers [67], emphasised chemists near-permanent station beside the furnace. Operations like distillation and sublimation had been used for centuries to resolve complex substances into their principles or constituents. In his efforts to separate and extract active essences from complex natural bodies, fire, the grand agent in the resolution of bodies ... 

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