The Gas-Oxygen Torch

For a small amount of material (<0.1 g), the method is simple and easy, using the basic technique of glass blowing. A piece of borosilicate glass tube, 5-6 mm inside diameter and about 30 cm long, is washed and dried in advance (Fig. A.2, (A)). First, one end of the tube is sealed with a narrow flame of a gas-oxygen torch. This is done by heating... 

In a drybox or drybag, stoichiometric amounts of tantalum pentachloride (25.1 g, 70 mmol) and sodium chloride (5.84 g, 100 mmol) are intimately mixed by grinding in a mortar. The mixture is placed in the Vycor reaction tube (see Fig. 1), and excess tantalum powder (58 g, 320 mmol) is added. Using a gas/ oxygen torch, the reaction vessel is sealed under a dynamic vacuum near the midpoint of its neck. 

Use a cadmium-free silver solder and a suitable silver-solder flux. You will need a gas-oxygen torch to make this seal (see Chapter 8 for information on gas-oxygen torches). Do not use a hissy torch flame because that indicates a flame too rich in oxygen. A soft blue flame is reducing and will prevent oxidation of the metal pieces, which prevents a good seal. 

Fig. 7.66 Removing a hole from a glass seal by removing the glass around the hole with a glass rod and a gas-oxygen torch (not shown).

This book is not an instruction book on glassblowing. Chapter 8 has some tips on gas-oxygen torch use, and Appendix D contains some recommended books for your consideration. The following discussion will also provide some of the... 

There are operations in the laboratory that require more flame heat than a Bunsen or Fisher burner can provide. For example, if you wish to fire-polish the end of a chipped glass tube or seal off (also called tip off ) a sample for NMR study, you will need to use a gas-oxygen torch. 

While some spectacular results can be shown by the action of the alurninum/oxygen torch, the use of a solid fuel and the fact that the flame is not self-sustaining and requires the presence of a pilot gas complicates the operation of such a torch. Actually, the alumi-Dum/oxygen flame probably owes its effectiveness to the heat concentration in the product, since at 3800 K peak temperature it is not spectacularly hot. One of the reasons may be that the stability of aluminum oxide (AlaOj) at very high temperature is relatively poor and the reaction... 

The processing of dental restorations is typically performed in air. Melting the alloy is done in air by using a gas-oxygen torch, induction furnace, or an electrical resistance furnace. Firing dental porcelain is also done in an oxidizing atmosphere, despite the term vacuum furnace. This situation has restricted the metallurgical systems used for dental restorations and is one reason for the... 

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