Glass forming tube drawing

For making thin-walled tubes of both smaller and larger diameters, in particular of borosilicate glasses, use is made of the Velio system based on drawing in the downward direction the formed tube is then deflected and pulled in the horizontal direction. 

Glass capillary arrays are now commercially available for laboratory use. They are formed by assembling a large number of parallel glass capillary tubes, heating to fuse and draw down to individual capillary diameters of 0.5 n. The bundle is then sliced to form thin discs with a regular capillary array. 

Unlike fused sUica, it can be produced by standard glass forming methods like tube draw,... 

If it is desired to observe the crystalline form of the osazone, draw up in a glass tube a few drops of the cold filtrate containing the fine crystals, and transfer to a microscope slide. Cover the drops with a slip and examine under the microscope unless the filtrate has been cooled very slowly and thus given moderately-sized crystals, the high power of the microscope will probably be required. Note the fine yellow needles aggregated in the form of sheaves. Compare with Fig. 63(A). 

The end of the capillary tube is heated until the glass is soft, then before it has time to cool it is touched on to the surface of a thin bubble of glass and a slight suction applied. This forms the window into a concave shape and draws it slightly down into the capillary, whose ends then protect it from damage. The bubble of thin glass should be thin enough to show interference colours. These windows will stand a vacuum provided atmospheric pressure is on the concave side of the window. If they are subjected to a pressure difference in the other direction, failure occurs due to the reversal of curvature. 

A method for making larger thin windows has been described by J. T. Lloyd (1949). For windows in the end of a tube he advocates the blowing of a thin-walled bulb at that end and then drawing it into the tube to form the window by the following method the thin-walled bulb is blown at the end, the wall of the tube is then heated all round at a short distance from the end imtil the glass is fused, and then the... 

Half fill a fiask with a sat. aq. soln. of sodium carbonate, and boil the liquid for 15-20 minutes until a little monohydrated carbonate is formed. Close the flask with a cork, fitted with two glass tubes, and keep the temp, at 10°-15° till some crystals are formed. Rim in alcohol of sp. gr. 0 835 and temp, of 45° until the flask is full. Crystals of the a-salt are formed after standing four or five days at a temp, of 16 22°. The crystals are isolated, by drawing on the mother liquid, and adding alcohol before the mother liquor is quite gone. The remaining mother liquor is then drawn off. 

Rhombic Sulphur. Pour 4-5 ml of chloroform into a dry test tube in a fume cupboard ) and spill in a sulphur powder in small portions, shaking the contents of the tube, until a saturated solution forms. Filter the solution into a porcelain bowl (do not wet the filter with water, why ), cover it with a glass, and let it stand in the fume cupboard for slow evaporation. Put a drop of the solution on a slide, cover it with a cover glass, and observe under a microscope how the crystals grow. Draw the sulphur crystals. 

The volatile liquid (boiling point, 22° melting point, —10°) must now be distilled from the U tube and sealed in a glass tube. Select a strong tube of suitable diameter of soft glass, seal one end, and blow it out to rounded form like a test tube. At a height of the tube such that the volume below will be about twice that of the liquid to be preserved, soften the tube and draw it to a constriction of such diameter that the smallest tubing... 

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