The Mel-Temp Apparatus

The Mel-Temp apparatus (Fig. 33) substitutes for the Thiele tube or open beaker and hot oil methods (see Using the Thiele Tube ). Before you use the apparatus, there are a few things you should look for. 

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With the Thiele tube (Fig. 39) you use hot oil to transfer heat evenly to your sample in a melting point capillary, just like the metal block of the Mel-Temp apparatus does. You heat the oil in the sidearm and it expands. The hot oil goes up the sidearm, warming your sample and thermometer as it touches them. Now, the oil is cooler and it falls to the bottom of the tube where it is heated again by a burner. This cycle goes on automatically as you do the melting point experiment in the Thiele tube. 

The Mel-Temp apparatus (Fig. 3) consists of an electrically heated aluminum block that accommodates three capillaries. The sample is illuminated through the lower port and observed with a 6-power lens through the upper port. The heating rate can be controlled, and with a special thermometer the apparatus can be used up to 500°C, far above the useful limit of silicone oil (about 350°C). It is also available with a digital thermometer. 

The Mel-Temp apparatus shown in Figure 2.19 is another electrical unit that utilizes a heated metal block rather than a liquid for transferring the heat to the capillary tube. A thermometer is inserted into a hole bored into the block, and the thermometer gives the temperature of the block and the capillary tube. Heating is accomplished by controlling the voltage applied to the heating element contained within the block. 

Equipment. All melting points were determined with a Mel-Temp apparatus from Laboratory Devices and are uncorrected. Gas chromatography was carried out on either a Varian Aerograph 700 or Hewlett-Packard 5880 chromatograph. Beckman IR-9 and Perkin Elmer FT-1800 spectrophotometers were used for the determination of mid-IR spectra. All NMR spectra were obtained using an IBM NR-80 FT spectrometer. Elemental analyses were determined for all new monomers and polymers by Micro-Tech Laboratories, Inc. of Skokie,... 

The melting point is determined conveniently with a Mel-Temp apparatus and a 90-510° thermometer designed for use with it (Laboratory Devices, Post Office Box 68, Cambridge 39, Massachusetts). An evacuated capillary containing a sample is... 

Melting points are uncorrected and were determined on a Mel-Temp apparatus. The structures of all novel compounds were confirmed by nmr, ir, and uv spectroscopy. Microanalyses were performed by Galbraith Laboratories, Knoxville, Tenn. Where analyses... 

Except for the Thomas-Hoover and Mel-Temp apparatus, the capillary is held to the thermometer with a rubber band made by cutting a slice off the end of a piece of ra-in. rubber tubing. This rubber band must be above the level of the oil bath otherwise, it will break in the hot oil. Insertion of a fresh tube under the rubber band is facilitated by leaving the used tube in place. The sample should be close to and on a level with the center of the thermometer bulb. 

The melting point of the product can be determined with a Mel-Temp apparatus and a 500° thermometer. To avoid oxidation, seal the sample in an evacuated capillary tube. 

Ketene generator (K-1), 529 Lithium-alkylamine reduction (L-1), 580 Manipulation of a noxious solid with rubber gloves, a powder funnel, and a dust mask (N-3), 717 Mel-Temp apparatus (D-3), 243 Mercury seal for stirrer (G-3), 416 Model of the complex Coi(CO)g CuHaC— CCsHt (D-1) for construction of cobalt atoms, see L. F. Fieser, J- Chem. Ed., 42, 408 (1965), 111 Molecular sieve crystals (M-2), 704... 

A glass bell is now inserted into the loaded melting-point capiUaiy, open end first (down), and allowed to fall (centrifuged if necessary) to the bottom. The assembled system (Fig. Llh) is then inserted onto the stage of aThomas-Hoover Uni-Melt Capillary Melting Point Apparatus (Fig. 4.3) or similar system (such as a Mel-Temp). 

All NMR spectra were obtained with a Bruker AMX 400 spectrometer. Melting points were determined on a Mel-Temp n apparatus and are uncorrected. The pyrolysis was conducted in a Biichi GKR-51 oven. LDA was purchased from Aldrich. Dry tetrahydrofuran was freshly distilled from Na/benzophenone. 

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