Conical neck

This type of filtration is almost invariably performed with the aid of a Buchner flask and funnel, by means of which a rapid and almost complete separation can be obtained. The Buchner flask A (Fig. 4) consists of a simple thick-walled conical flask with a short side-arm for connection to a water-pump. Into the neck of the flask is fitted the Buchner funnel B which consists usually of a cylindrical porcelain funnel, the bed of which is pierced by a... 

Add 15 g, of chloroacetic acid to 300 ml. of aqueous ammonia solution d, o-88o) contained in a 750 ml. conical flask. (The manipulation of the concentrated ammonia should preferably be carried out in a fume-cupboard, and great care taken to avoid ammonia fumes.) Cork the flask loosely and set aside overnight at room temperature. Now concentrate the solution to about 30 ml. by distillation under reduced pressure. For this purpose, place the solution in a suitable distilling-flask with some fragments of unglazed porcelain, fit a capillary tube to the neck of the flask, and connect the flask through a water-condenser and receiver to a water-pump then heat the flask carefully on a water-bath. Make the concentrated solution up to 40 ml. by the addition of water, filter, and then add 250 ml. of methanol. Cool the solution in ice-water, stir well, and set aside for ca. I hour, when the precipitation of the glycine will be complete. 

Place 5 ml. of benzaldehyde in a wide-necked stout-walled bottle of about 100 ml. capacity (a conical flask is too fragile for this purpose) and add 50 ml. of concentrated dy 0 880) ammonia solution. Cork the bottle securely, shake vigorously, and then allow to stand for 24 hours, by which time the layer of benzaldehyde at the bottom of the bottle will have been converted into a hard mass of hydrobenzamide. (If after 24 hours the crude hydrobenzamide is still syrupy, shake the mixture vigorously and allow to stand for another hour, when the conversion will be complete.) Break up the solid pellet with a strong spatula, filter at the pump, wash with water and drain thoroughly. Recrystallise from ethanol methylated spirit should not be used, as it contains sufficient water to cause partial hydrolysis back to benzaldehyde and ammonia. Hydrobenzamide is obtained as colourless crystals, m.p. 101° (and not 110° as frequently quoted) yield, 4 g. 

Place 20 g. of dry powdered benzoic acid in C, add 15 ml. (25 g., i.e., a 30% excess) of thionyl chloride and some fragments of porcelain, and then clamp the apparatus on a boiling water-bath as shown so that no liquid can collect in the side-arm of C. Heat for one hour (with occasional gentle shaking), by which time the evolution of gas will be complete. Cool the flask C, detach the condenser and fit it to the side-arm for distillation, using a 360° thermometer for the neck of C. To the lower end of the condenser fit a small conical flask G (Fig. 67(B)) by a cork carrying also a calcium chloride tube. 

The principle of this method has been explained above. The reaction is best carried out in a wide-necked 250 ml. conical flask for which a cork having the usual two delivery-tubes for steam-distillation is available when the Strictly termed iV-methylaniline. t. Strictly termed iV,i -dimcthyliiniline. 

Assemble an apparatus similar to that used in the prenous experiment, i.e., a 500 ml. conical flask fitted at the neck with a freshly-charged calcium chloride tube, a dropping-funnel, and in addition an outlet-tube joined to the water-pump so that dry air can be drawn through the calcium chloride tube and thence through the conical flask. The purpose of the air-stream is to remove as much as possible of the excess of hydrogen chloride. 

A simple apparatus for sublimation in a stream of air or inert gas is shown in Fig. II, 45, 2.. 4 is a wide-necked conical flask provided with... 

Flasks. Round-bottomed, flat-bottomed, conical (Erlenmeyer) and bolt-head flasks up to a capacity of 2-3 litres are generally fitted with a 524 socket f those from 5 to 100 ml. are available with a 514 or 519 (from 25 ml.) socket. Round- and flat-bottomed flasks exceeding 1 litre in capacity are supplied with 534 necks. Whilst all sizes of sockets can be obtained from the manufacturers, it is usually convenient to limit the socket sizes to a small number (say, 514, 519, 524 and 534), thus per mitting interchangeability with the minimum number of adapters. 

Place 5-2 g. (5 ml.) of anihne and 45 ml. of 10 per cent, aqueous sodium hydroxide solution in a wide-necked bottle (or, bF not available, a conical flask), and then add 8 -5 g. (7 ml.) of benzoyl chloride, stopper, and shake vigorously for 10-15 minutes. Heat is evolved in the reaction. The crude benzoyl derivative separates as a white powder. When the reaction is complete (t.e., when the odour of benzoyl chloride can no longer be detected smell cautiously), make sure that the reaction mixture is... 

In a 500 ml. conical flask place 50 ml. of glachtl acetic acid, 25 ml. of 40 per cent, formaldehyde solution (formalin) and 20 g. of phenol. Wrap a cloth or towel loosely around the neck and opening of the flask. Pass dry hydrogen chloride gas (Section 11,48,1) into the mixture. Within 5 minutes, a large mass of pink plastic is formed the reaction is sometimes very vigorous. The yield is 36 g. It is frequently necessary to break the flask in order to remove the product completely for this reason a beaker, or metal flask or beaker, is preferable. 

To test the delivery time, again separate the components of the stopcock, dry, grease and reassemble, then fill the burette to the zero mark with distilled water, and place in the holder. Adjust the position of the burette so that the jet comes inside the neck of a conical flask standing on the base of the burette stand, but does not touch the side of the flask. Open the stopcock fully, and note the time taken for the meniscus to reach the lowest graduation mark of the burette this should agree closely with the time marked on the burette, and in any case, must fall within the limits laid down by BS 846 (1985). 

For evaporation at the boiling point either a conical flask with a short Pyrex funnel in the mouth or a round-bottomed flask inclined at an angle of about 45° may be employed in the latter the drops of liquid, etc., thrown up by the ebullition or by effervescence will be retained by striking the inside of the flask, while gas and vapour will escape freely. When organic solvents are employed the flask should be fitted with a swan-neck tube and a condenser so that the solvent is recovered. 

Procedure (indirect method). Weigh out accurately 0.1-0.2 g of the ammonium salt into a 500 mL Pyrex conical flask, and add 100 mL of standard 0.1M sodium hydroxide. Place a small funnel in the neck of the flask in order to prevent mechanical loss, and boil the mixture until a piece of filter paper moistened with mercury(I) nitrate solution and held in the escaping steam is no longer turned black. Cool the solution, add a few drops of methyl red, and titrate with standard 0.1M hydrochloric acid. Repeat the determination. 

Discussion. Very pure silver can be obtained commercially, and a standard solution can be prepared by dissolving a known weight (say, 10.787 g) in nitric acid in a conical flask having a funnel in the neck to prevent mechanical loss, and making up to a known volume (say, 1 L for a 0.1 M solution). The presence of acid must, however, be avoided in determinations with potassium chromate as indicator or in determinations employing adsorption indicators. It is therefore preferable to employ a neutral solution prepared by dissolving silver nitrate (relative molecular mass, 169.87) in water. 

Illustration Satellite formation in capillary breakup. The distribution of drops produced upon disintegration of a thread at rest is a unique function of the viscosity ratio. Tjahjadi et al. (1992) showed through inspection of experiments and numerical simulations that up to 19 satellite drops between the two larger mother drops could be formed. The number of satellite drops decreased as the viscosity ratio was increased. In low-viscosity systems p < 0(0.1)] the breakup mechanism is self-repeating Every pinch-off results in the formation of a rounded surface and a conical one the conical surface then becomes bulbous and a neck forms near the end, which again pinches off and the process repeats (Fig. 21). There is excellent agreement between numerical simulations and the experimental results (Fig. 21). 

---