Melting point capillary

No glass melting point capillaries need be prepared. 

The student should read Sections 1,10 to 1,16 carefully before commencing any experimental work. A supply of melting point capillaries is prepared as described in Section 11,10 (compare Fig. 77, R , I). The apparatus illustrated in Fig. 77. 10, 2, a is assembled with concentrated sulphuric acid as the bath liquid the thermometer selected should have a small bulb. The melting points of pure samples of the following compounds are determined in the manner detailed in Section 11,10 —... 

Purification of the radioactive tracer was modified to include a fractional sublimation before a single extraction—recrystallization cycle to conserve the tracer material. Microgram samples were prepared in melting point capillaries for assay by mass spectroscopic analysis (Table III), made by direct probe injection of the sample into the ion source (18). The probe was heated rapidly to 200°C, and mass spectra were obtained during vaporization of the sample. Tri-, tetra-, and pentachlorodibenzo-p-dioxins vaporized simultaneously with no observed fractionation. 

The direct insertion probe consists of a metal sample holder drilled to accept standard melting point capillaries up to 1 inch in length. This is inserted into the ion source through a vacuum lock and may be heated to 250°C at varying rates. 

The procedure we have adopted for introducing samples into the MS-9 is shown in Figure 6. It provides reproducible analyses at a high level of sensitivity. The sample tubes are made from 1 mm id melting point capillaries. A Hamilton 10-pl syringe is used to introduce a 3-4 pi portion of the residue into the sample tube. With a small flame the sample tube is drawn out just above the level of the liquid to produce a capillary constriction about 20 mm long. The solvent is then... 

You usually take melting points in thin, closed end tubes called capillary tubes. They are also called melting point tubes or even melting point capillaries. The terms are interchangeable, and I ll use all three. 

Capillary tube stage. Inasemicircleaboutthebottomofthejacketed thermometer, yet behind the thermometer periscope, are five holes through which you can put your melting point capillaries. 

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. 

Here you use a loaded melting point capillary tube (see Loading the Melting Point Tube ) and attach it directly to the thermometer. The thermometer, unfortunately, has bulges there are some problems, and you may snap the tube while attaching it to the thermometer. 

Put the center of a melting point capillary into a small, blue Bunsen burner flame. Hold it there until the tube softens and starts to sag. Do not rotate the tube, ever. 

By means of a melting point capillary and a water bath, the transition point from red to black is easily observed, The procedure may be hastened by pre-heating the bath to about 65°C. 

Melting point capillary tube, 1.5 X 100 mm Oven at 100°C Heat lamp... 

Methyl phenyl sulfoxide is extremely hygroscopic The melting point is best taken by rapid transfer of the easily supercooled oil to a melting-point capillary b> means of a finely drawn pipet The sealed capillary is then cooled to effect crystallization of the sulfoxide... 

Obtain a melting point capillary tube. One end of the tube will be sealed. The tube is packed with solid in the following way ... 

Attach the melting point capillary tube to the thermometer by means of a rubber ring. Align the mercury bulb of the thermometer so that the tip of the melting point capillary containing the solid is next to it (Fig. 15.3). 

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). 

---