Tube Furnace: Porcelain Tube Wound with Platinum Wire in a Heat-Retaining Jacket (Stansfield, 1914)

The laboratory tube furnace: a porcelain tube wound with a spiral of platinum wire and wrapped in a heat-retaining jacket. Current through the wire heats the tube and whatever is inside it. A gas can be passed through the tube, the work watched through windows at the ends, and the temperature read with a thermocouple pushed in from one end. Result: a small furnace for heating a material in any chosen gas at moderate temperatures, well short of platinum's melting point. Source: A. Stansfield, The Electric Furnace: Its Construction, Operation and Uses (2nd ed., 1914), pp. 24-25 and 154. Unknown: sizes, the jacket material, current and voltage. Picture: Stansfield, Fig. 13.

中级

2 days

说明

Wind the tube

Take a tube of porcelain; fire-clay, silica or alundum also serve. Wind a spiral of platinum wire round it, leaving the leads free. Fix the turns so they cannot shift or touch each other when the wire expands with the heat, or they will short-circuit. Platinum foil can be wound instead of wire: its larger surface heats faster for the same weight of platinum. Not given: sizes, wire gauge, number of turns.

此步骤所需材料：

瓷管1 个

铂丝1 as required

所需工具：

钳子套装

未知尺寸

Jacket it

Enclose the wound tube in a heat-retaining envelope, so the heat stays in the tube. The tube ends stick out through the envelope. Not given: the envelope material.

此步骤所需材料：

未知材料1 heat-retaining envelope

所需工具：

未知尺寸

Fit windows and the thermocouple

Close the tube ends with windows of glass or mica to watch the work. Push a thermocouple pyrometer in from one end and watch from the other. Leave a way in and out at the ends when you want a stream of gas through the tube.

此步骤所需材料：

云母片1 end windows

所需工具：

带读数的热电偶

Heat

Put the material in the tube and pass current through the wire. The wire can run at any temperature below platinum's melting point (1,755 °C, 3,200 °F, as the book gives it). In practice the tube and envelope limit the furnace to temperatures far below that. Nickel or nichrome coils are cheaper, but they cannot go as hot and in time they oxidise. Not given: current and voltage.

所需工具：

带读数的热电偶