Hand torches

There are two basic methods of making these joints, (i) by the use of a bench torch and holding both tubes, (2) by the use of a hand torch and clamping the tubes (or one of them). 

Generally speaking it is best to make internal seals using a bench torch and rotating the glass in the flame. If this is not practicable it is possible to work with a hand torch with the glass clamped if Method... 

A Claisen flask of the type shown in Figure 48, II, has a wide side arm sealed into its neck at an angle which, for convenience, is about 45°. Any liquid in the side arm will then readily nm back into the flask. A 45° joint of this kind can be made quite easily with a hand torch a round end is put on the side arm, using a bench torch, and a hole is blown in this round end so that the plane in which the hole lies is at 45° to the tube axis. The wide side arm is joined to the flask neck, and the small side arm is then joined on. 

The prepared flask is supported so that the tube B can be sealed to a vacuum system. If a suitable furnace is available the flask is surrounded by this, with the constriction A still within reach of the hand torch flame otherwise the heating must be done by flame. A liquid air trap is included between the flask and diffusion pump. With a vacuuih of below 10 mm of mercury the temperature of the flask is raised to near the softening point—the heating may be rapid... 

With tubing up to about 30 mm in diameter the whole bend can be annealed by flame at the finish, but above this diameter it is advisable to anneal each portion for a few minutes after it is bent and shaped, and before one moves on to the next portion. With extra large tubing it is better to have two workers, one on either side of the tube, each with a hand torch. 

To make the seal one of the tubes is clamped vertically and the preoxidized disc is placed centrally upon the flare of this tube. Working round the tube with a hand torch the glass is softened and the disc fused into place. With the seal still hot, the tube is removed from the clamp and, rotating by hand in a bench flame, the second glass flare... 

Alternatively, the whole water-circulating part can be made separately and internally sealed into the wide tube, using a hand torch, and... 

The ring seal at A is made in the early stages and is partially annealed. This part of the assembly is then inserted into the prepared tube B which is held clamped, and, when seated well, is itself clamped at C (Figure 62, II). Using a hand torch and exerting care to warm... 

With intricate apparatus, particularly when a hand torch is being... 

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