Buchner funnel and flask

When crystallisation is complete, the mixture of crystals and crude mother-liquor is filtered at the pump, again using a Buchner funnel and flask as described on p. 10, and the crystals remaining in the funnel are then pressed well down with a spatula whilst continual suction of the pump is applied, in order to drain the mother-liquor from the crystals as effectively as possible. If it has been found in the preliminary tests that the crystalline material is almost insoluble in the cold solvent, the crystals in the... 

Add 5 g. of potassium hydrogen tartrate and 5 g. of antimony trioxide (each being finely powdered) to 30 ml. of water contained in a small flask, and boil the mixture under a reflux water-condenser for 15 minutes. Then filter hot, using a Buchner funnel and flask which have been preheated by the filtration of some boiling distilled water. Pour the clear filtrate into a beaker and allow to cool. Potassium antimonyl tartrate separates as colourless crystals. Filter, drain and dry. Yield, 5 g. The product can be recrystallised from hot water, but this is usually not necessary. 

Dissolve 5 g. of aniline hydrochloride in 120 ml. of hot water contained in a 200 ml. conical flask and then add 4 g. of potassium cyanate. Heat the solution on a water-bath for 30 minutes, adding about 1-2 g. of animal charcoal towards the end of the heating if a slight turbidity has developed. Now bring the solution quickly to the boil over a gauze, and filter it at the pump, using a Buchner funnel and flask which have been preheated by the filtration of some boiling distilled water. The clear... 

When the ij hours boiling is complete, preheat a Buchner funnel and flask by pouring some boiling water through the funnel with the filter-paper already in position, and then quickly filter the boiling solution. Transfer the filtrate to a beaker to cool, and then wash the insoluble residue of diphenylurea on the filter twice with hot water, and drain thoroughly. Cool the filtrate in ice-water the monophenylurea separates as colourless needles. Filter at the pump and drain well. Recrystallise the crude product from boiling water, as in the previous preparation. Yield of monophenylurea, 2 5-3 g. m.p. 147°. 

The insoluble residue of diphenylurea from the original filtration is chemically almost pure. It may be recrystallised from hot rectified spirit or ethanol, a process which will be necessary if the material contains fragments of porcelain. When using either of these solvents, however, the hot solution should be filtered at the pump using a small Buchner funnel and flask which again have been preheated by the filtration of some of the hot solvent, as the solution when cooled rapidly deposits the diphenylurea. iSym-Diphenylurea (or carbanilide) is thus obtained as fine colourless crystals, m.p. 237° yield, 1-1 5 S ... 

Place 27 g. of o-phenylenediamine (Section IV,92) in a 250 ml. round-bottomed flask and add 17 -5 g. (16 ml.) of 90 per cent, formic acid (1). Heat the mixture on a water bath at 100° for 2 hours. Cool, add 10 per cent sodium hydroxide solution slowly, with constant rotation of the flask, until the mixture is just alkaline to litmus. Filter off the crude benzimidazole at the pump, wash with ice-cold water, drain well and wash again with 25 ml. of cold water. Dissolve the crude product in 400 ml. of boiling water, add 2 g. of decolourising carbon, and digest for 16 minutes. Filter rapidly at the pump through a pre heated Buchner funnel and flask. Cool the filtrate to about 10°, filter off the benzimidazole, wash with 25 ml. of cold water, and dry at 100°. The yield of pure benzimidazole, m.p. 171-172°, is 26 g. 

Filtration by means of suction is generally employed where possible in the operations of organic chemistry, since more rapid and more complete separation of the mother liquor is in this way effected. For this purpose several types of apparatus are in use. For large quantities of material the Buchner funnel and flask (Fig. 27) are used, the filter paper being cut... 

Apparatus for filtration, Buchner funnel and flask, water aspirator... 

Round-bottomed flask (250 mL) Magnetic stirrer and stirrer bar Buchner funnel and flask... 

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