Melting points capillary-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. 

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

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). 

Do as many melting point determinations as your instructor may require. Just remember to use a new melting point capillary tube for each melting point determination. 

Melting Point-Capillary Tube Method (Cc 1-25) determines the temperature at which... 

Apparatus Use any suitable commercial or other apparatus. Use melting-point capillary tubes—id, 1 mm od, 2 mm length, 50 to 80 mm and open at both ends. 

Under similar conditions, 1 reacts with Na2Se to give PPSe in only 5% yield. When prepared as noted above and with Se in DMF, PPSe is a yellow powder with a melting point (capillary tube) of ca. 220° and a compositional range, from elemental analysis,... 

Microscale Inverted Capillary Method. In microscale experiments, there often is too little product available to use the semimicroscale method just described. However, the method can be scaled down in the following manner. The liquid is placed in a 1-mm melting-point capillary tube to a depth of about 4-6 mm (see Figure 13.4B). Use a syringe or a Pasteur pipette that has had its tip drawn thinner to transfer the liquid into the capillary tube. It may be necessary to use a centrifuge to transfer the liquid to the bottom of fhe tube. Next, prepare an appropriately sized inverted capillary, or bell. 

Some solids sublime before they melt, making a determination of a melting point impossible using a standard melting-point capillary tube. How could you modify your capillary tube to obtain a melting point for such a compound ... 

An alternative technique for preparing the glass bells follows heat the midsection of an open-ended melting point capillary tube and then draw the glass to form a smaller capillary section. This section is then broken approximately in the middle and each open end is sealed. The appropriate length for the bell is then broken off. Thus, two bells are obtained, one from each section. The sealing... 

Samples analyzed by El mass spectrometry must be converted to gas phase. For pure gases or volatile liquids the samples may be introduced directly through a small orifice that allows an appropriate amount of material into the vacuum chamber. A small amount of a solid sample can be placed in a melting point capillary tube and inserted into the mass spectrometer at the end of a metal rod, called a direct insertion probe (DIP).The temperature at the tip of the probe can be varied to promote sublimation of the sample. Another common method of sample introduction is gas chromatography, which is the ideal choice for samples that are impure. 

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