Flask filter

H. The stem of G fits through the bung J to the filter-flask as shown. A bent tube K, Imown as a Pregl filter-tube, is fitted through another bung L into the upper neck of the funnel G. 

To prepare the funnel G, fit it to the filter-flask and wash it by passing distilled water, ethanol and acetone through the glass plate H. Remove G from the bung J, wipe it with a clean cloth, and dry it in an oven for 15 minutes at 140°. Then carefully wipe it again with the cloth, and place it in the balance case on the carrier D (Fig. 90) for 15 minutes to attain an equilibrium with the air. Then transfer it to the balance pan and weigh. 

Now fit the weighed funnel G again to the filter-flask, and attach the Pregl filter-tube K as shown (Fig. 21). Apply 2i gentle suction from the water-pump, and dip the open limb of the tube K just below the surface of the liquid in the Carius tube. Draw off the supernatant liquid a little at a time until rather less than 1 ml. remains. Now gently shake the mixture in the Carius tube, and try to adjust the suction so... 

Solvents with boiling points above 90-95°. The apparatus of Fig. 77,13, 3 (with closed filter flask and rubber lead-off tube) or of Fig. 77,13, 4 (see discussion in previous paragraph but one) should be vtilised vrith an air bath or oil bath as the source of heat. Heating on a Wire gauze is not recommended. 

The technique of the filtration of hot solutions has already been described in Section 11,28. The filtration of cold solutions will now be considered this operation is usually carried out when it is desired to separate a crystalline solid from the mother liquor in which it is suspended. When substantial quantities of a solid are to be handled, a Buchner funnel of convenient size is employed. The ordinary Buchner fimnel (Fig. 11,1, 7, a) consists of a cylindrical porcelain funnel carrying a fixed, flat, perforated porcelain plate. It is fitted by means of a rubber stopper or a good cork into the neck of a thick-walled filtering flask (also termed filter flask, Buchner flask or suction flask) (Fig. 11,1, 7, c), which is connected by means of thick-walled rubber tubing (rubber pressure tubing) to a similar flask or safety bottle, and the latter is attached by rubber pressure tubing to a filter pump the safety bottle or trap is essential since a sudden fall in water pressure may result in the water sucking back. The use of suction renders rapid filtration possihle... 

When exhausting desiccators, a filter flask trap (see Fig. 77, 19, 2) should always be inserted between the desiccator and the pump. The vacuum should be applied gradually and should not exceed about 50 cm. of mercury for models (a), (6) and (d). These desiccators may withstand lower pressures, but it is generally considered unsafe to exhaust below this pressure unless the precaution be taken of surrounding the desiccator by a cage of fine-mesh steel wire collapse of the desiccator will then do no harm.J Models (c) and (e) may be exhausted to about 20 mm. of mercury a steel wire cage must be provided for this low pressure. 

When the adsorbent has been introduced into the tube, the latter is fitted into a filter flask (see Fig. 77, 46, 2) to which a pump is attached the pump is run slowly and the column is again pressed down gently with the wooden pestle. The circumference of the upper surface is gently and uniformly tapped, especially where it is in contact with the glass surface, for about one minute air bubbles and channels are thus avoided when the solution is poured in. Some workers place a loose plug of cotton wool or a circle of filter paper at the top of the column in order to protect the solid from disturbance when the liquid is introduced. 

Sulphuric acid method. Place 20 g. of commercial cycZohexanol and 0-6 ml. of concentrated sulphuric acid in a 150 or 200 ml. round-bottomed or bolt head flask, add 2-3 chips of porous porcelain, and mix well. Fit the flask with a fractionating column, a Liebig condenser, adapter and filter flask receiver as in Section 111,10 (1). Heat the flask in an air bath (Fig. II, 5, 3) at such a rate that the temperature at the top of the column does not rise above 90° alternatively, an oil bath, heated to a temperature of 130-140°, may be used. Stop the distillation when only a small residue remains and the odour of sulphur dioxide is apparent. Transfer the distillate to a small separatory funnel. 

Alternatively, the tube from the top of the condenser may be supported just abovi the surface of water in a filter flask (as in Fig. 11, 13, 8). 

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. 

Dissolve 180 g. of commercial ammonium carbonate in 150 ml. of warm water (40-50°) in a 700 ml. flask. Cool to room temperature and add 200 ml. of concentrated ammonia solution (sp. gr. 0 88). Introduce slowly, with swirling of the contents of the flask, a solution of 50 g. of chloroacetic acid (Section 111,125) in 50 ml. of water [CAUTION do not allow chloroacetic acid to come into contact with the skin as unpleasant burns will result]. Close the flask with a solid rubber stopper and fix a thin copper wire to hold the stopper in place do not moisten the portion of the stopper in contact with the glass as this lubrication will cause the stopper to slide out of the flask. Allow the flask to stand for 24-48 hours at room temperature. Transfer the mixture to a distilling flask and distil in a closed apparatus until the volume is reduced to 100-110 ml. A convenient arrangement is to insert a drawn-out capillary tube into the flask, attach a Liebig s condenser, the lower end of which fits into a filter flask (compare Fig.//, 1) and connect the... 

Method 3. Fit up the apparatus shown in Fig. 7F, 45, 1 using a 250-ml, roimd-bottomed flask. Do not pass water through the glass jacket since the condenser wUl be employed only as an air condenser the empty filter flask is used merely as a trap to prevent the escape of vapours into... 

Iodine monochlorlde may be prepared as follows. Pass dry chlorine into 127 g. of iodine contained in a 125 ml. distilling flask until the weight has increased by 34-6 g. The chlorine should be led in at or below the surface of the iodine whilst the flask is gently shaken it is essential to have an excess of iodine. Distil the iodine chloride in an ordinary distillation apparatus use a filter flask, protected from atmospheric moisture by a calcium chloride (or cotton wool) guard tube, as a receiver. Collect the fraction b.p. 97-105° the jdeld is 140 g. Preserve the iodine monochloride in a dry, glass-stoppered bottle. 

The function of the trap is to condense the hexane from the n-butyl-lithium solution. The checkers used a 1-L three-necked flask fitted with a short delivery tube (a quick fit air bleed tube was used), stopper, and rubber tubing connection. The submitters used a water aspirator and a 1-L filter flask with a drying tower between. 

NaBH4 has also been crystd from isopropylamine by dissolving it in the solvent at reflux, cooling, filtering and allowing the solution to stand in a filter flask connected to a Dry-ice/acetone trap. After most of the solvent was passed over into the cold trap, crystals were removed with forceps, washed with dry diethyl ether and dried under vacuum. [Kim and Itoh J Phys Chem 91 126 1987.] Somewhat less pure crystals were obtained more rapidly by using Soxhlet extraction with only a small amount of solvent and extracting for about 8h. The... 

A gas bunbling device is attached to the dry-ice condenser. A simple apparatus consists of two 500-ml. filtering flasks equipped with... 

A. 3-Amino-2,4,6-tribromohenzoic acid. The bromination apparatus consists of a 2-1. three-necked standard-taper flask A, equipped with a Trubore stirrer and attached by rubber stoppers and glass tubing to two filter flasks, B and C, as shown... 

Care is essential to avoid spillages. A fine eapillary tube eonneeted to a filter flask and filter pump should be used immediately to eolleet any spillage. Surfaees, e.g. floors, eontaminated by minute mereury droplets should be treated with sulphur or zine dust, or by use of a eommereial elean-up kit. 

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