CUTTING AND BENDING OF GLASS TUBING

A batswing or fish-tail burner is generally used for the bending of soda glass tubing. Both hands are used to hold the tube in the length of the flame (Fig. 

The usual Griffin form of beaker with spout, Fig. 2.39(a), is widely used. Sizes between 5 ml and 6 litres are available. The conical beaker, Fig. 2.39(h), occasionally finds use in preparative work. Some designs have a Teflon (PTFE) rim 

When it is required to filter hot solutions, as for example in recrystallisations employing decolourising charcoal (Section 2.20), a heated jacket around the filtration funnel is necessary. A simple, inexpensive form is shown in Fig. 2.42 it consists of a coil made of copper of about 10 mm diameter forming a 60° cone which may be readily constructed in the laboratory workshop. Hot water or steam is passed through the coil, hence it is very suitable for the filtration of flammable liquids. The coil may also be used in cold filtration and in some forms of sublimation apparatus (Section 2.21) by circulating ice-cooled water 

The Buchner and Hirsch funnels, and the filter flasks and tubes, are available with interchangeable ground glass joints (for example, Fig. 2.43(f)). The Buchner funnel is also available with a screw-thread side-arm for easy attachment via a plastic hose connector to the vacuum line (Bibby Science Products). 

Spatulas in stainless steel, nickel, flexible horn, or moulded polythene are available commercially. One such design of palette knife has a flexible stainless steel blade provided with a wooden handle. Nickel spatulas may have tumed-up ends, or spoon- or blade-shaped ends, and are available in sizes from 100 mm x 5 mm (for semimicro work) to 200 mm x 10 mm (for macro work). 

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Cut off the delivery tube at a distance of about 1.5 cm. from the neck and seal on a tube B of thin glass 1.3 cm. in diameter and 50 cm. to act as an air condenser, bending the tube as shown in the figure. Make a tube C shaped like a pipette the wide part of which will just slip into the neck of the flask. The lower end is of very small tubing drawn to a capillary at the tip. When the tip is almost at the bottom of the flask, the upper part of the narrow tube should be just above the outlet into the condenser tube. The wide tube should extend about 3 cm. above the end of the neck of the flask and should then contract to a short, narrow tube over which a short piece of rubber tubing, provided with a pinch cock F, is slipped. 

Insertion of a glass tube into a rubber connector or adapter or hose is easy if the glass is lubricated with a very small drop of glycerol. Grasp the tube very close to the end to be inserted if it is grasped at a distance, especially at the bend, the pressure applied for insertion may break the tube and result in a serious cut. 

In this experiment you will cut, fire-polish, bend, and draw out small glass tubing. Although glass rod will not be used in this experiment, the same procedures can be used to cut, fire-polish, bend, and draw out small glass rod. At the same time, you may make a number of pieces that will be used in apparatus for later experiments. 

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