Nichrome resistance

Electric tube furnaces of appropriate dimensions are available from various manufacturers. A model RO 4/25 by Heraeus GmbH, Hanau, FRG is suitable. However, a very satisfactory furnace can be built by any well equipped laboratory workshop at little cost and effort. The material required consists of thin walled ceramic tubing, 3.5 cm i.d., nichrome resistance wire, heat resistant insulation, and ordinary hardware material. A technical drawing will be provided by the submitters upon request. The temperature of the furnace can be adjusted by an electronic temperature controller using a thermocouple sensor. A 1.5 kW-Variac transformer and any high temperature thermometer would do as well for the budget-minded chemist. 

A 100 volt nichrome resistance wire was used to ignite the soaked cloths at four ignition points. Eight cut drum—can halves were connected by the gasoline soaked cloths. (Refer to Figure 5.29)... 

Since the bypass system has demonstrated good feasibility, the complex burner with its electronic controls may be replaced by a simple resistance heater powered by the alternator on the vehicle see Fig. 12. A small air pump (3-5 CFM) is used to transfer heat from the heater to the filter and provide sufficient oxygen for soot oxidation. Typical heaters arc fabricated from two nichrome resistance elements contained in MgO powder insulation with a 0.260-in.-diameter stainless steel sheath. The energy requirement for regeneration is typically 3 kW and is readily achieved from a 90-amp alternator at a speed of 6400 rpm. 

Gas chromatography coupled with AAS has been the most popular hyphenated technique for the speciation of metals and organometals. Among different atomizer designs employed in coupling GC with AAS, electrothermal atomization, especially the electrother-mally heated quartz tube, is preferred because of its high sensitivity, simple operation, and low cost [6]. The quartz tube (—100 X 10 mm inner diameter) is usually constructed in house and wrapped with Nichrome resistance wire and ceramic isolation material. A thermocouple is attached to the surface of the quartz burner for temperature control (Fig. 1). If necessary, hydrogen and air can be supplied from side arms of the burner. The furnace can be heated to more than 1000°C by means of a variable transformer. 

The bath temperature may be controlled by heating with an immersed loop of Nichrome resistance coil, such as the heating element from an electrical appliance. The coil is connected to a 110-volt line in series with a 27-ohm 5-ampere variable resistor and a 600-watt heater element, which may be cut out of the circuit to lower the fixed resistance. An ammeter in the circuit helps to determine the proper adjustment of the sliding contact of the resistor. To avoid an excessive load on the coil,... 

C, has been described by Wendiandt (112). The sample holder and furnace arrangement are shown in Figure 11.28. The sample A, in the form of a pressed disk (1x5 mm) was placed between two platinum electrodes (7.0 mm in diameter). Leads to the electrodes were led out of the furnace area by one-holed ceramic insulator tubes. To maintain a constant tension on the sample disk by the electrodes, one electrode is spring-loaded at H. The furnace consists of a Nichrome resistance wire heater element on a Vycor tube suitably insulated with a ceramic material- A clamp G secures the tube furnace to the base. Furnace temperature, Tf, is detected by a Chromel-Alumel thermocouple located at D. The other components of the EC apparatus are the same as those previously described. The apparatus was used oil pure... 

In the case of the sulfur-rich mixtures of sulfur and phosphorus, approximately 120 grams of the mixture was placed in a borosilicate glass beaker, which was covered with a niobium plate at the higher temperatures (>350°C) to decrease sulfur losses by vaporization. The cell was placed in a 500 ml alumina secondary container, and this assembly was located inside a sealed stainless steel vessel which was heated by Nichrome resistance wire. The cover of the vessel had access ports for a stirring... 

The purification-reduction furnace now used is shown in Fig. 6.14. It includes a J in. thick stainless-steel retort of about 6 ft depth and just over 2 ft internal diameter, heated electrically by three independently controlled nichrome resistance windings. The top heating zone, rated at 13 kW, extends about 11 in. down the reactor around an annular trough, which is partially filled with a lead-containing eutectic melting at 247°C. 

Electrically heated oil baths, which typically contain either mineral oil or silicone oil, are commonly employed in the laboratory. These baths are heated either by placing the bath container on a hot plate or by inserting a coil of Nichrome resistance wire in the bath. In the latter case, the resistance wire serves as the heating element and is attached to a transformer with an electrical cord and plug (Fig. 2.24). Thermal equilibration within the bath is maintained by placing a paper clip or stirbar in the bath and using a magnetic stirrer (Sec. 2.11). 

B. Nichrome resistance wire (powered with a variac)... 

Figure 4.3 Suggested methods to shrink heat shrink tubing (A) heat gun with concentrator adapter (B) nichrome resistance wire (powered with a variac).

The Caldwell-Reswick electrode is a helix of nichrome resistance wire filled internally with a silicone rubber core. A retaining hook is located on the distal end The electrode is placed by means of a 23-gauge hypodermic needle in the same manner as the cardiac electrode shown in Figure 8.1. This electrode can be placed directly into a muscle. The silastic core and the helical assembly minimize electrode breakage. Placement and removal of the electrode is quick and easy. 

The furnace was made by winding a nichrome resistance wire around a quartz tube 6cm long, 4mm od, 2mm id. This unit was placed inside another quartz tube (7cm long, 8mm od, 6mm id). The nichrome wire coil was connected to a 0-230-V Variac transformer. The circuit was equipped with a voltmeter and ammeter. The furnace was operated... 

Methods of platen construction were developed to produce heated platens capable of 900°C and continuous operation in excess of two years 07,520 hours) by utilizing Inconel and various steels for the platen body, dependent on temperatures, and nichrome resistive heaters encased in ceramic... 

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