Prism process

Gas separation through membranes achieved commercialization after the introduction of the Prism process by Monsanto a decade ago. Originated for hydrogen recovery, high area membrane equipment is now used for other gases, notably C02 [1]. Hydrogen, carbon dioxide, and other components are now being removed from mixtures on an industrial scale [2, 3],... 

The racemic acid is not a primary product of plant processes but is formed readily from the dextrorotatory acid by heating alone or with strong alkaU or strong acid. The methods by which such racemic compounds can be separated into the optically active modifications were devised by Pasteur and were apphed first to the racemic acid. Racemic acid crystallizes as the dihydrate triclinic prisms. It becomes anhydrous on drying at 110°C... 

Crystalline Structures. Crystal shape of amino acids varies widely, for example, monoclinic prisms in glycine and orthorhombic needles in L-alanine. X-ray crystallographic analyses of 23 amino acids have been described (31). L-Glutamic acid crystallizes in two polymorphic forms (a and P) (32), and the a-form is mote facdely handled in industrial processes. The crystal stmeture has been determined (33) and is shown in Figure 1. 

Thebaine, CjgHgiOgN. This base, which occurs in opium to the extent of 0-1 to 1 per cent., was first obtained by Pelletier and Thiboumery, who regarded it as isomeric with morphine, and named it paramorphine. It was examined by Kane, who first called it thebaine, and by Anderson, who described a method of isolation and provided the formula given above. It remains in the mother liquor after the removal of morphine and eodeine hydrochlorides in Gregory s process, and in Hesse s method of isolating it from this source is obtained as the acid tartrate. This is crystallised from hot water, and the alkaloid regenerated from it is reerystallised from dilute alcohol, from which it separates in leaflets, or from dry alcohol in prisms, m.p. 193°, — 218-6° (EtOH) or — 229-5°... 

This formula was confirmed hy Haworth and Perkin s synthesis of a-flZZocryptopine from herherine, the first application of a process, of which examples have heen given already in the syntheses of cryptopine (p. 298) and protopine (p. 301) hy the same authors. Anhydrotetrahydromethyl-herherine (I cf. hase (a), p. 346) in dry chloroform was added to a solution of perhenzoic acid in ether cooled helow 5°. The amine oxide, C21H23O5N (II), separated as an oil, which after shaking with sodium hydroxide solution, solidified and was crystallised from water in slender prisms, m.p. 135°. It was dissolved in acetic acid, hydrochloric acid added, the mixture heated in boiling water for an hour and the hase precipitated hy addition of potassium hydroxide. The precipitate was dissolved in methyl alcohol, ether added, the alcohol washed out with water and the ethereal... 

As the refractive index of fluids varies with the temperature, it is of importance to know the temperature of the fluid contained in the double prism during the process of measurement. 

With flame emission spectroscopy, there is greater likelihood of spectral interferences when the line emission of the element to be determined and those due to interfering substances are of similar wavelength, than with atomic absorption spectroscopy. Obviously some of such interferences may be eliminated by improved resolution of the instrument, e.g. by use of a prism rather than a filter, but in certain cases it may be necessary to select other, non-interfering, lines for the determination. In some cases it may even be necessary to separate the element to be determined from interfering elements by a separation process such as ion exchange or solvent extraction (see Chapters 6, 7). 

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