Large-volume runs

Nickel shells that are electroformed or vaporformed when suitably backed up and mounted in a frame are also excellent materials for large-volume runs. For activities of less than 50,000 parts per year, aluminum forgings of Alcoa grade No. 7075-T73 machines to the needed configuration will perform satisfactorily. They have the advantage of good heat conductivity, an important feature in RIM. 

Large volumes of gas are generated, primarily ethane and ethylene, from the disproportionation of the ethyl radicals produced in the reaction of ethylmagnesium bromide with ferric chloride. The reaction should be carried out in an efficient hood, or else a tube should be run from the top of the reflux condenser to a hood. 

It is seen that, although the dimensions and particle sizes may not be precisely matched, all three columns are of a size closely similar to those commercially available with, perhaps, the exception of the long high efficiency column. The small 3 cm column is excellent for the preliminary assessment of a sample. As a result of its size it does not use large volumes of solvent and can be quickly reconditioned after a separation in readiness for the next run. It is very convenient for choosing the best phase system in method development. The other columns would be chosen on a basis of the efficiency required to separate the critical pair in the reduced chromatogram of the sample for analysis. 

HPLC runs involve relatively large volumes of a solvent however, by the nse of dedicated interfaces, this is no more a problem, and bands eluted from HPLC can be transferred to a GC or to a mass spectrometry (MS). The interface is the hearth of the HPLC-MS hyphenation, and it mnst be able to eliminate solvent and to perform the ionization of the analytes in order to separate them on the basis of the ratio mass/charge. 

In development or small clinical production runs, complete liquid medium may be most convenient. Economic issues may dictate that at large-scale powdered or liquid concentrate medium be used. Shipment and storage of large volumes of complete liquid medium is less practical at scales greater than 1000 L. 

The large volume solvents, trichloroethylene and perchloroethylene, are still chiefly made from acetylene, but appreciable amounts of the former are derived from ethylene. The competitive situation between these source materials runs through the whole chlorinated hydrocarbon picture, and extends on to other compound classes as well—for example, acrylonitrile is just on the threshold of a severalfold expansion, as demand grows for synthetic fibers based thereon. Acrylonitrile can be made either from ethylene oxide and hydrogen cyanide, from acetylene and hydrogen cyanide, or from allylamines. The ethylene oxide route is reported to be the only one in current commercial use, but new facilities now under construction will involve the addition of hydrogen cyanide to acetylene (27). 

In a 500 cc. round-bottom flask, fitted with a mechanical stirrer, is placed 290 g. (2.49 moles) of chlorosulfonic acid (Note 1). The flask is surrounded by a cooling bath and cooled with running water to about 12-150. To the chlorosulfonic acid is added gradually 67.5 g. (0.5 moles) of acetanilide. This requires about fifteen minutes if the temperature is maintained at approxi mately 15°. Since large volumes of hydrogen chloride are evolved, the reaction should be conducted in a good hood. After all of the acetanilide has been added, the mixture is heated to 6o° for two hours to complete the reaction (Note 2). 

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