Side arms

The thermometer should be so arranged that the top of the bulb is just level with the centre of the side-arm of the distilling-flask. 

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... 

When a more delicate fractional vacuum-distillation is required, the flask and column shown in Fig. ii(b), p. 26, may be used, the side-arm of the column being fitted directly into receiver C (Fig. 14). A rubber stopper must then be used to fit the flask on to the fractionating column, and it should also carry a capillary tube leading to the bottom of the flask, to provide the usual fine stream of bubbles to prevent bumping. 

Reflux Distillation Unit. The apparatus shown in Fig. 38 is a specially designed distillation-unit that can be used for boiling liquids under reflux, followed by distillation. The unit consists of a vertical water-condenser A, the top of which is fused to the side-arm condenser B. The flask C is attached by a cork to A. This apparatus is particularly suitable for the hydrolysis of esters (p. 99) and anilides (p. 109), on a small scale. For example an ester is heated under reflux with sodium hydroxide solution while water is passed through the vertical condenser water is then run out of the vertical condenser and passed through the inclined condenser. The rate of heating is increased and any volatile product will then distil over. 

The complete filtration apparatus is shown in Fig. 5, p. 11. A simpler and cheaper apparatus is shown in Fig. 45. This consists of a boiling-tube A having a side-arm for connection to the pump the tube A is conveniently held in a wooden or cork block B or in a clamp. The funnel F may be fitted into A through a pliable rubber disc D the latter is more useful than a cork since it covers tubes of various diameters. The filtrate is collected in the centrifuge-tube T. 

X 5 Glass tube receiver with sloping side arm. (As in Fig. 37.)... 

Fit a 500 ml. bolt-head flask F with a well-fitting cork which is free from flaws, and which carries a dropping-funnel D and a delivery tube (or knee-tube ) T, the latter being connected to a water-condenser C (Fig. 52). Attach an adaptor A to the lower end of the condenser. (Alternatively, use a ground-glass flask (Fig. 22(a), p. 43) with a distillation-head (Fig. 22(F)) the dropping-funnel can be fitted into the distillation-head, the side-arm of which is connected to a condenser as in Fig. 23(0), p. 45.)... 

Fit a 250 ml. round-bottomed flask with a refllix water-condenser down which pieces of sodium may be dropped alternatively, use a flask having a short straight stoppered side-arm for this purpose. 

Distil the filtered ethereal solution, using a 100 ml. flask fitted with a dropping-funnel and a side-arm for the condenser observe all the normal precautions for ether distillation (p. 162) and run the ethereal solution into the flask as fast as the ether distils over. When all the ether has distilled off, detach and cool the flask, when the oily colourless residue of saligenin will rapidly crystallise. Weight of product, 5-0 g. m.p. 75-82°. Recrystallise either from a mixture of benzene and petroleum (b.p. 60-80°), or from a minimum of water, allowing the stirred aqueous solution to cool to 65-70° before chilling. The dry crystalline saligenin has m.p. 85-86°. 

For this preparation, which must be performed in the fume-cupboard, assemble the apparatus shown in Fig. 67(A). C is a 150 ml. distilling-flask, to the neck of which is fitted a reflux single-surface water-condenser D, closed at the top E by a calcium chloride tube. The side-arm of C carries a cork F which fits the end E of the condenser for subsequent distillation. The side-arm of C is meanwhile plugged by a small rubber cork, or by a short length of glass rod. (Alternatively, use the ground-glass flask and condenser (Fig. 22 (a) and (c), p. 43), and... 

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. 

In place of the conical flask G, a small Buchner flask may be used with the calcium chloride tube fitted to the side-arm, but in either case a duplicate flask for the second fraction should be available. 

Cool the flask in ice-water and pour the ethereal solution into a mixture of about 6 ml. of dil. H2SO4 and 10 g. of crushed ice contained in a 50 ml. flask fitted for steam-distillation, taking care to leave behind any unchanged magnesium. Fit to the lower end of the condenser a small Buchner flask or boiling-tube with side-arm (45°) carrying a piece of rubber tubing which falls well below the level of the bench. 

Fit a 75-100 ml. Claisen flask with a small dropping-funnel in the main neck, and a water-condenser to the side-arm, and then run the... 

The pure quinaldine can now be isolated by either of the following methods, (a) Transfer the acetylated mixture to a Claisen flask (preferably having a short fractionating column below the side-arm) and distil the mixture slowly at water-pump pressure by heating the flask in an oil or silicone bath. The first fraction, of b.p. ca. 50715 mm., contains acetic acid and... 

The apparatus consists of a tube T (Fig. 76) usually of total height about 75 cm. the upper portion of the tube has an internal diameter of about I cm., whilst the lower portion is blown out as shown into a bulb of about 100 ml. capacity. Near the top of T is the delivery-tube D of coarse-bored capillary, bent as shown. The tube T is suspended in an outer glass jacket J which contains the heating liquid this jacket is fitted around T by a split cork F which has a vertical groove cut or filed m the side to allow the subsequent expansion of the air in J. The open end of the side-arm D can be placed in a trough W containing water, end a tube C, calibrated in ml. from the top downwards, can be secured ts shown over the open end of D. 

Then again remove T, and drop a weighed pellet of the solute through the side arm A. Stir the mixture until a clear solution is obtained, and then repeat the above process until three consistent readings of the freezing point of the solution have been obtained. Then add a second weighed pellet of the solute, and determine the freezing-p>oint of this more concentrated solution in the same way. 

If the solute is a liquid, introduce it into the apparatus from an ordinary pyknometer tube (Fig. 80), weighing the tube before and after. For this purpose, insert the delivery-tube of the pyknometer carefully down the side-arm A (Fig. 79) so that the liquid falls well into the body of T. Force the liquid... 

If a small Beckmann thermometer, similar to that used in the Sucharda-Bobranski method (p. 442) is available, the above method can be readily modified by replacing the tube T (Fig. 79) by an ordinary small boiling-tube without the side-arm A. The thermometer B and the stirrer S are fitted as in Fig. 79. The volume of solvent (usually ca 5 ml.) must of course cover the bulb of the thermometer. 

When three consistent readings are obtained, add a weighed pellet of the solute to T for this purpose it is important that the thermometer is not withdrawn, and the boiling is not interrupted. It is best to hold the pellet ready in a pair of forceps near the mouth of the side-arm of T, and then momentarily to remove the condenser, drop in the pellet and replace the condenser when the condenser is removed a small quantity of cold air entering the side-arm will cause slight condensation of the hot vapour, none of which will therefore escape. 

The combustion tube. The oxygen is led through the side-arm G (Fig. 85) into the combustion tube L via the horizontal side-arm H which is fused into the combustion tube about 4 cm. from the end (the joint between G and H is also made with impregnated rubber tubing with the two glass tubes touching inside the rubber). The position of H thus allows the combustion... 

When in position, the side-arm k of the carbon dioxide absorption tube is ttached to the T side-arm of the water absorption tube R (Fig. 85) by impreg-... 

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