Plugs, glass wool

If a clear solution of n-butyl-lithium is required for any purpose, it may be decanted through a glass wool plug as detailed under 2-Phenylpyridine, Note 4. 

A 50 mL or 100 mL burette, with Pyrex glass-wool plug or sintered-glass disc at the lower end, can generally be used for the determinations described below alternatively, the column with side arm (Fig. 7.4a) is equally convenient in practice for student use. Reference will be made to the Duolite resins the equivalent Amberlite or other resin (see Table 7.1 in Section 7.1) may of course be used. 

An alternative elution technique is to transfer the powder (e.g. for bromophenol blue) to a glass column fitted with a glass-wool plug or glass sinter, and elute the dye with ethanol containing a little ammonia. The eluted solution, made up to a fixed volume in a small graduated flask, may be used for colorimetric/ spectrophotometric analysis of the recovered dye (see Chapter 17). A calibration curve must, of course, be constructed for each of the individual compounds. 

Silica gel column cleanup. Prepare a silica gel column by placing a glass-wool plug in the bottom of a glass chromatography column. Slurry 18g of silica gel with hexane-ethyl acetate (4 1, v/v) and pour the slurry into the column. Rinse the walls of the column with hexane-ethyl acetate, and add approximately 2 g of sodium sulfate to the top of the silica gel column. Drain the solvent to the top of the sodium sulfate layer. 

Dichloromethane partition. Transfer the aqueous extract into a 500-mL separatory funnel and add 150 mL of 5% sodium chloride solution. Rinse the round-bottom flask with 80 mL of dichloromethane and transfer into the separatory funnel. Shake the separatory funnel vigorously (with occasional venting) for 1 min and allow the phases to separate. Drain the lower dichloromethane through sodium sulfate (approximately 50 g suspended on a glass-wool plug in a 10-cm diameter filter funnel, pre-rinsed with 25 mL of dichloromethane) into a 500-mL round-bottom flask. Repeat the partition with another 80-mL portion of dichloromethane. Drain the dichloromethane through the sodium sulfate as before, and rinse the sodium sulfate with three 10-mL portions of dichloromethane. Evaporate the combined dichloromethane extract just to dryness using rotary evaporation under reduced pressure in a <40 °C water-bath. 

When all the iodine has sublimed out of tube C (10 to 12 hours), nitrogen is admitted into the system, and the apparatus is allowed to cool to room temperature. Tube C is removed, and the glass-wool plugs and unreacted titanium (0.23 g.) are removed with a hooked copper wire while purging with nitrogen. Caution. Care should be exercised in removing the unreacted titanium from the tube the titanium may be pyrophoric. Then tube C is cleaned, dried, and reattached to tube B. Tube B is removed from attachment to A and, while holding tube B... 

The cathode is a rolled strip of copper gauze which fits snugly into a 3 X in. test tube and rests on a glass-wool plug which covers a hole of about -in. diameter blown in the bottom of the test tube. During the preparation, the solution about half fills the tube, and the glass-wool plug protects the bulk of the oxidized solution from the cathode. 

E) neck constricted to about 3.5 cm. o.d. (F) loose-fitting glass-wool plug (G) sand and decaborane mixture (H) 500-ml. flask. 

In the adsorption with Tenax alone satisfactory results were obtained, while in the presence of mineral oil a considerable proportion of the organophos-phorus pesticides (particularly Malathion and Parathion-methyl) was not adsorbed and was recovered in the filtered water. This drawback can be overcome by adding a layer of Celite 545 which, in order to prevent blocking of the column, is mixed with silanised glass wool plugs. A number of analyses of surface and estuarine sea waters were carried out by this modified Tenax column and simultaneously by the liquid-liquid extraction technique. To some of the samples taken, standard mixtures of pesticides were also added, each at the level of 1 xg/l (i.e., in concentration from 13 to 500 times higher than that usually found in the waters analysed). One recovery trial also specifically concerned polychlorobiphenyls. The results obtained in these tests show that the two extraction methods, when applied to surface waters that were not filtered before extraction, yielded very similar results for many insecticides, with the exception of compounds of the DDT series, for which discordant results were frequently obtained. 

Controlled furnace-type pyrolyser a, heater b, A1 block c, variable transformer d, gas outlet to column e, Swagelok union f, column oven g, gas inlet h, cement i, glass wool plug j, insulating block k, pyrometer 1, stainless steel chamber m, sample n, heater thermocouple o, pyrolysis tube p, ceramic tube q, line voltage. 

In the case of soil analysis, a 2.0cm i.d.x30cm column is used. Stones, roots and other gross impurities were removed, and the soil was reduced to a size between 30 and 60 mesh. 20g of soil was packed into the column between two glass wool plugs. Insecticides were desorbed from the soil by passing small volumes of acetone toluene (1 1) through the column at a rate... 

The reaction is monitored by 1H NMR with sample preparation as follows A 0.3-mL aliquot of the reaction mixture is removed and concentrated under reduced pressure for 10 min. The resulting residue is dissolved in 0.5 mL of methyl sulfoxide-d (DMSO-d6> (Cambridge Isotope Labs) and filtered through a pipette with a glass wool plug directly into an NMR tube. The sample is checked on a Bruker ARX-500 MHz instrument. The checker used a Bruker 300 MHz instrument, which sufficed. 

Durham, NC). Under these conditions the temperature of the air stream midway through Section B was 50 C and had dropped to 30°C upon reaching the filter (Section C). Aliquots of the air stream were withdrawn through the septum in Section B and analyzed by glc/ecd in order to determine the air stream concentration. After termination of air flow, the filter, glass wool plug and sorbent, if any, were extracted with acetone and the extracts analyzed by glc/ecd. The apparatus from the injection port to the filters was rinsed with acetone and analyzed to determine the TRIS which was surface absorbed. 

We obtained the best results with the Carbopack B-DA/4% Carbowax 20M, 80-120 mesh Supelco column, 2000 x 2 mm. It was initially conditioned for 21 h at 245°C, but the normal running temperature is 175°C. The injector/detector temperature is 200°C and a flame ionization detector is used. A glass sleeve is fitted to the injector and the glass wool plug removed from the column inlet. The carrier gas is nitrogen with a flowrate of 40 ml min at 310 kN m. The sample solution (9 ml) is mixed with 1 ml of pivalic acid solution (1.5% m/v) as internal standard. Then 1 ml of this solution is mixed with 1 ml 0.3 M oxalic acid solution and 3 ml deionized water before injecting 1 pi into the septum. 

Fig. 1. All dimensions in centimeters, (a) 2-cm-thick glass wool plugs (b) IrCl3 on silica gel (c) Pyrex jacket for thermocouple (d) 24/40 J joint (e) Kontes 24/25 Teflon adapter with O-ring seals (f) thermocouple leads to indicating controller (g) outlet to H2S04 bubbler by way of trap (h) 2-mrri double oblique Teflon stopcock (i) N2 inlet (/ ) CO or Cl2 inlet.

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