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. 

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