Vacuum extraction flask

Figure 2. Vacuum extraction flask for headspace seawater collection and analysis. Seawater is added to the fill line, and the flask is pressurized with zero...

In these equations P is the headspace pressure in atmospheres, a is the gas-to-seawater ratio (Vg/V ), and is the total volume of the flask (here 1 L). By this procedure the initial concentration of a dissolved gas (C f) in seawater can be determined. Normally single extractions are done, but subsequent extractions can be used to check the amount of gas remaining in the seawater. The uncertainties associated with the headspace method can be evaluated by referring to Equation 2. In addition to the headspace gas concentration, Cg, the uncertainty in C f is dependent on the uncertainties in H and the ratio a. By using a propagation of error procedure on Equation 2, the uncertainties associated with the vacuum extraction flask can be estimated for different gases (2). The results show that for a gas that is not very soluble (H > 3), the total uncertainty is 5 %. For a more soluble gas H < 0.5) whose Henry s constant is not accurately known in seawater, the uncertainty is 30 %. 

Comparisons of the vacuum extraction flask method versus the purge-cryogenic trap method were made on duplicate seawater samples. The results are shown in Table II. The compounds measured represent a wide range of Henry s constants (solubilities) and provide a representative evaluation of the two methods. In Run 1 of Table II the CHCI3 concentration was not measured. In Runs 1-4 the CF2CI2 concentrations were below the detection limit of the GC-ECD used for the analysis. The comparisons are for single samples and agree reasonably well except for 1,1,1-trichloroeth-... 

When the ester has cooled to room temperature, the sulfuric acid is neutralized with a strong solution of sodium carbonate the ester (upper layer) is separated, and the aqueous solution extracted with ether, or preferably benzene about one-tenth of the yield is in the extract. The combined products are placed in a i-l. vacuum distillation flask and distilled under reduced pressure, after the bulk of the solvent and accompanying alcohol and water has been removed. When the temperature of the distillate reaches 94°/i6 mm. the receiver is changed, and the ester collected from 94° to 990, most of it coming over at 97-98°/i6 mm. (Note 3). The temperature of the oil bath should not rise above 1450. A small amount (about 60 g.) of residue remains in the flask. The yield is 490-550 g. (65-75 per cent of the theoretical amount). The total time necessary for the preparation of this quantity of ester is about twenty-four hours. 

The purified pine bark tannin was obtained in the following manner. The phloem of freshly felled loblolly pine trees was removed by carefully peeling the outer bark away at the cork cambium and then peeling the white phloem from the xylem cambium. Strips of phloem were cut into sections of about 2 to 5 in2 and immediately immersed in acetone-water (70 30, v/v). The extraction flasks were kept at ambient temperature, protected from exposure to light, for 48 hr, after which the solvent was recovered by filtration. The acetone was removed under vacuum on a rotary evaporator, and the aqueous solution was extracted four times with an approximately equal volume of ethyl acetate to remove low molecular weight phenolics. The remaining water-soluble extract was freeze-dried. Aliquots (about 50 gm) were redissolved in methanol-water (1 1, v/v), and the solutions were applied to 2.4 X 90 cm Sephadex LH-20 columns packed in this same solvent. The columns were eluted with methanol-water until no more colored material was eluted. The condensed tannin polymers absorbed... 

To prevent losses, air currents must be strictly avoided while scraping off the spot and transferring the powder to a suitable vessel. Various authors have accordingly used vacuum extractors, with which the localised spots could be sucked on to the filter surface or into the extraction flask and then eluted [65, 70,123, 318, 349, 437, 451,463, 578, 605, 651]. 

Mix 50 ml. of formalin, containing about 37 per cent, of formaldehyde, with 40 ml. of concentrated ammonia solution (sp. gr. 0- 88) in a 200 ml. round-bottomed flask. Insert a two-holed cork or rubber stopper carrying a capillary tube drawn out at the lower end (as for vacuum distillation) and reaching almost to the bottom of the flask, and also a short outlet tube connected through a filter flask to a water pump. Evaporate the contents of the flask as far as possible on a water bath under reduced pressure. Add a further 40 ml. of concentrated ammonia solution and repeat the evaporation. Attach a reflux condenser to the flask, add sufficient absolute ethyl alcohol (about 100 ml.) in small portions to dissolve most of the residue, heat under reflux for a few minutes and filter the hot alcoholic extract, preferably through a hot water fuimel (all flames in the vicinity must be extinguished). When cold, filter the hexamine, wash it with a little absolute alcohol, and dry in the air. The yield is 10 g. Treat the filtrate with an equal volume of dry ether and cool in ice. A fiulher 2 g. of hexamine is obtained. 

The yellow solution was poured into 150 ml of water. After addition of 20 g of ammonium chloride and vigorous shaking, the layers were separated. The aqueous layer was extracted twice with diethyl ether. The combined solutions were dried over magnesium sulfate and concentrated in a water-pump vacuum. The residue was distilled at low pressure giving the desired carbinol, (b.p. 40°C/0.1 mmHg), n 1.5505 in 66-702 yield. A small viscous residue remained in the distillation flask. 

To a solution of 22 g of K0-tert.-Ci,H9 (see Exp. 4, note 2) in 400 ml of anhydrous liquid ammonia were added 22 g of the bis-ether (note 1). After stirring for 4 h, 20 g of powdered ammonium chloride were introduced in small portions. The ammonia was removed by placing the flask in a water-bath at 40°C, then 200 ml of water were added and five extractions with small portions of redistilled pentane were carried out. The combined extracts were washed with water, dried over magnesium sulfate and then concentrated in a water-pump vacuum. The residue was carefully distilled through a 40-cm Vigreux column, giving the allenic bis-ether,... 

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