Melting point capillaries, filling

Use an extension clamp to support the Thiele tube on a ring stand. Add mineral oil or silicone oil to the Thiele tube, and fill to a level above the top of the side arm. Use a thermometer clamp to support the thermometer with the attached melting point capillary tube in the oil. The bulb and capillary tube should be immersed in the oil keep the rubber ring and open end of the capillary tube out of the oil (Fig. 15.4). 

To provide an internal reference, the solvent is sealed in a capillary, which is placed at the bottom of the NMR tube used for the sample solution. For this purpose, a melting-point capillary is closed at one end and a syringe is used to add the reference solution. For aqueous studies, a 2% solution of t-butyl alcohol in water can be used as reference and as solvent for the paramagnetic solute. The shift with respect to the methyl resonance of the r-butyl group is then monitored. With organic ligands such as acetylacetonate (acac) groups, complexes such as Cr(acac)3, Fe(acac)3, and Co(acac)2 are soluble in benzene and the proton resonance of the solvent is a convenient reference. The capillary is filled one-third full, the lower end of the capillary is cooled in ice, and the upper part is sealed off with a small hot flame. Alternatively, the reference solution can be placed in one compartment of a coaxial pair of cyhndrical NMR tubes, which are available commercially. In either case the spectral display should be expanded to permit an accurate measurement of the frequency shift. 

In a generalized Adler method, one end of a capillary tube (1 Xl disposable micropipette, 3 cm long with an internal diameter of 0.2 mm) is flame sealed. The entire capillary tube is then quickly passed through a flame, and while warm, the open end is plunged into a reservoir containing the test chemical dissolved in chemotaxis medium. The liquid is drawn up into the capillary as it cools and the filled capillary is then withdrawn from the reservoir and inserted into a chemotaxis chamber, which is constructed by placing a U-shaped melting point capillary tube between a microscope slide and a coverslip (Fig. 1.2). The chamber is filled with an appropriate chemotaxis medium and inoculated with bacteria so that the final concentration is approximately 6 x 10 cells/ml. After a 1-h incubation, the capillary is removed from the chamber and the exterior rinsed with sterile water. The sealed end of the capillary is then broken and the contents are... 

One milliliter each of the borneol solution and the oxidizing solution are mixed in a test tube and briefly shaken. A TLC slide is spotted with the borneol solution, the camphor solution, and the ether layer of the reaction mixture. Spotting is done by means of a capillary melting point tube used as a dropper and filled with a 5 mm sample. The slide is developed in a wide-mouth jar containing a filter paper liner and a few milliliters of chloroform (Fig. A3.20). After development (the solvent front rises to within 1 cm of the top), the slide is removed, the solvent is allowed to evaporate, and the slide is placed in a covered wide-mouth jar containing a few crystals of iodine. The spots readily become visible and the progress of the reaction can easily be followed. With periodic shaking, the oxidation is complete in about 30 minutes. 

The heating liquid is pure concentrated sulphuric acid, with which the bulb of the flask is three-quarters filled. The substance, in powder form, is introduced into a small, thin-walled capillary tube. Such tubes are made as follows from test tubes (preferably from damaged tubes which must, however, be clean and dry ). The tubes are rotated in the flame of the blow-pipe till soft and then drawn out rapidly already after short practice the student can strike the correct diameter, which should be 1 0-1 -5 mm. internally. Suitable portions of the drawn-out material are cut off with scissors. It is convenient to cut double lengths (about 12 cm.), so that by sealing each length in the middle (micro-burner) two melting-point tubes are obtained ready for use. 

Melting points are important for determining the purity of solid products. A small amount of sample is packed into the closed end of a capillary tube with a wire or small glass rod. It is then attached to a thermometer, keeping the sample next to the bulb as shown (see Figure 19). Next submerge into oil filled tube, keeping setup in the middle of tube (do not touch the sides or bottom). Watch for temperature at which solid sample melts. 

The electrolyte has a particular structure. A mixture of LiA102 and alkali carbonates (typically >50 vol%) is hot pressed (about 5000 psi) at temperatures slightly below the melting point of the carbonate salts. In this way, a porous matrix support material of ceramic particles (LiA102) is formed that contains a capillary network filled with molten electrolyte. The ceramic material in the electrolyte structure represents a mechanical resistance which does not participate in the electrical or electrochemical processes. The prepared electrolyte has a thickness of 1-2 mm, and it is very difficult to produce it in large shapes. 

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