Freezing pressure filters

Preparation of filters in slabs or in powders suitable to be placed on air channels in fluidized beds or else as selective adsorbants on process lines. In recent years we made interesting approaches at COGEM A in this field using freeze-dried silica and alumina for the retention of radionuclides, acid droplets, and contaminants in the ventilation ducts of nuclear plants. Besides their great efficiency and low pressure drop the most interesting feature of these freeze-dried filters is that they can withstand extreme pH conditions and high temperatures. 

Physical pretreatment also has an important role to play not just to improve the performance of filters in general but in the case of vacuum filters it may even decide whether or not a vacuum filter can be used at all. Without such pre-treatment, a generally more expensive pressure filter may have to be used. Pretreatment may include crystallization, freezing, temperature adjustment, thermal treatment or ageing, but the three main methods used with vacuum filters are ... 

Filter-pump, 44 Filtration through cloth, 131 under reduced pressure, 43 with fluted filter, 53 "Fischer s ester method, 133 Fluorescein, 187 Fluted filter, 53 Formic acid, 106 Fractional distillation, 136 Fractionating columns, 137 Freezing-point method, 32 I -riedel-Crafis reaction, 210 furnace, combustion, 4 tube, 23 ... 

The solvent was evaporated off under reduced pressure, and the residual gum refluxed with concentrated hydrochloric acid (50 g) for 6 hours. The solution was aliowed to cool overnight. It was filtered from the phthalic acid crystals, and freeze-dried, and to the pink residue was added acetone (160 g) and ethyl acetate (50 g). The mixture was left in the cold room overnight and the clear pink supernatant liquid poured off. The pink gummy hydrochloride remaining in the flask was dissolved in water (20 g), saturated sodium acetate solution added until precipitation was complete, and the product collected and dried in a desiccator. The crude p-bis-(2-chloroethyl)-aminophenylalanine (3.6 g) was crystallized from methanol giving colorless needles, MP 172° to 174°C (decomp.) of p-bis-(2-chloroethyl)-aminophenylalanine. 

Filter layers, frost penetration, and cap-liner connections are other factors to consider in designing the closure system for a hazardous waste landfill. Before using geotextiles for filter layers in closures, one should conduct pressure tests and clogging tests on the material. Freeze-thaw cycles probably have little effect on membranes, but their impact on clay is still not known. Because of this lack of knowledge, membrane and clay layers should be placed below the frost penetration layer. Finally, a cap membrane should not be welded to the primary FML. Differential settlement in the cap can put tension on the cap membrane. In such a situation, the seam could separate and increase the potential for integration of the surface water collection system into the LDS. 

Negative atmospheric pressure chemical ionization (APC) low-energy collision activation mss spectrometry has also been employed for the characterization of flavonoids in extracts of fresh herbs. Besides the separation, quantitative determination and identification of flavonoids, the objective of the study was the comparison of the efficacy of the various detection systems in the analysis of flavonoids in herb extracts. Freeze-dried herbs (0.5g of chives, cress, dill, lovage, mint, oregano, parsley, rosemary, tarragon and thyme) were ground and extracted with 20 ml of 62.5 per cent aqueous methanol. After sedimentation the suspension was filtered and used for HPLC analyses. Separations were carried out in an... 

The filtrate, obtained after the crystals of bis-(4-iminopentane-2-ono) copper (II) were filtered off, was evaporated under reduced pressure. The residue was extracted with water, the extracts were filtered, and the filtrate was treated with sodium hydroxide and p-toluenesulfonyl chloride (18). In this way, about 30% of the 1,3-propanediamine was accounted for as the crude ditosylate (identity confirmed by lack of freezing-point depression with authentic sample), but only a trace of diamine could be detected in the distillate. 

Tetralin [119-64-2] M 132.2, n 65-66°/5mm, 207.6 /760mm, d 0.968, n 1.5413. It was washed with successive portions of cone H2SO4 until the acid layer no longer became coloured, then washed with aq 10% Na2CO3, and then distd water. Dried (CaSO4 or Na2SO4), filtered, refluxed and fractionally distd at under reduced pressure from sodium or BaO. It can also be purified by repeated fractional freezing. 

Dried, either by azeotropic removal of water with benzene or toluene, or by stirring 20g of P2O5 with 500ml of the acid at 100° for 0.5h. Then distd under vacuum and fractionally crystd by partial freezing. Sulphuric acid, if present, can be removed by prior addition of Ba(OH)2 to a dilute soln, filtering off the BaSQ4 and concentrating under reduced pressure, and is sufficiently pure for most applications. 

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