Collar flasks

The so-called collar flasks (Figure 22)63 are remarkable for their simplicity. The very short neck of the boiling flask presents very little hindrance to the passage of vapor from the evaporation surface in this flask to the condensation surface of the condenser, so that use of such flasks comes very close to short-path distillation proper. 

Various types of collar flask permit distillation of any amount of liquid between 50 mg and 5 g. For 50-1000 mg quantities the flask (Figures 22a and 22 b) is filled with thin-fibre glass wool, preferably by use of a glass tube that is thin enough to pass through the narrow neck of the flask, and the substance to be distilled is placed on the glass wool by means of a suction ball. Any solvent present is removed at room temperature by application of a slight vacuum, then the apparatus is immersed up to the vacuum tube in a water-bath and is warmed later it is immersed to half-way up the neck in a paraffin... 

Figure 22. Distillation apparatus involving collar flasks.

Alternatively a mercury-sealed stirrer may be employed. Here again a short glass tube C is inserted through the cork of the flask to act as a collar for the stirrer. The tube C carries a short wide tube B which is either fused at its lower end to C, or is fixed to it by means of a cork as shown. The stirrer D carries a precisely similar tube E, the top of which however is now fixed to D the bore of the tube E allows it to fit easily within the annular space between the collar C and the tube B. Mercury... 

All thermometers for semi-micro preparations must have very small bulbs. They may often be inserted into flasks through a short collar of rubber tubing in place of the customary corks. 

Kragen, m. collar cape flange, -kolben, m. flanged flask. 

A 1-1. three-necked round-bottomed flask is fitted with a 50-ml. separatory funnel and a mechanical stirrer sealed with a well-lubricated rubber collar. A stopper in the third neck of the flask carries a glass tube that reaches to the bottom of the flask, enters the top of a 1-1. separatory funnel, and extends down to the stopcock. 

Efficient stirring in the flasks A and B is provided by means of suitably sized Teflon-covered magnetic followers fitted with half-inch Teflon collars the magnetic stirrer units serve also to further support the apparatus which should be securely clamped to a rack. 

Place the fiiihiiil irilb thi collar/seal note that lie funnel has a point at the bottom of the stem. Make sure that this point is as far away as possible from the vacuuin attachment side arm of the receiver flask, since the filtering iiquid runs off this point and if the point is near the vacuum inlet, the liquid may be drawn into the side artn and then into the trap or water pump (see IB above). 

Place die correct-sized Buchner collar in the neck of the receiving flask it should sit well into the neck and fit the funnel to form a good seal. 

Filtration flask (1 or 2 L) with a rubber collar to fit SPE columns. Attach to house vacuum or water-driven aspirator column. 

Commercial sublimation adapters such as those shown in Figure 2.59 are available for microscale work. A Winston adapter is normally used with a sublimation chamber such as a 3- or 5-mL conical vial (Fig. 2.59a), whereas adjustable adapters may be used with 5- or 10-mL round-bottom flasks (Fig. 2.59b). In both cases a cold-finger that may be connected to a vacuum source is fitted to the chamber containing the substance to be sublimed, and the connection is secured with a standard-taper joint that is often accompanied by an O-ring and threaded collar (Fig. 2.59). The cold-finger can be filled with ice or dry ice. The advantage of using... 

Extract the combined distillate fractions, which you collected in the centrifuge tube, with three successive 2-mL portions of methylene chloride (3 X 2 mL). Use the first portion of methylene chloride to rinse the collection collar of the Hickman stiU. After each extraction, transfer the lower methylene chloride layer (Pasteur filter pipet) to a 25-mL Erlenmeyer flask. 

Here mention will be made of the distillation of small amounts of substances for which so-called Hickmann flasks are used, which can be given various shapes. The simplest type is represented in Fig. 3a. They are advantageous because they do not cause losses due to the scattering of the distilled liquid and its vapors on superfluous surfaces. For the distillation of more volatile substances they can be provided with condensers for the distillation of larger amounts of liquids they are provided with a side tube to lead the distillate from the collar for vacuum distillation another tube is sealed to the flask used for the insertion of the capillary, and if the separa-... 

Jacketed Sample Tube— A double-walled, unalvoed vessel, similar to a Dewar flask, the qiace between the samide tube and the outer glass jacket being filled at atmo dieiic pressure with dry nitrogen or air. The mouth of the tube shall be closed with a cork stopper siq rting the thermometer and moisture proof collar throng which the stirrer passes (Fig. 1). 

Measure out 25 1 mL of the fuel and transfer it to the clean, dry, jacketed sample tube. Close the tube tightly with the cork holding the stirrer, thermometer, and moisture proof collar and adjust the thermometer position so that its bulb does not touch the walls of the tube flask and is approximately in the center. The bulb of the thermometer should be 10 to 15 mm from the bottom ofthe sample tube. 

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