Illustrated Guide to Home Chemistry Experiments

Chapter 5: Mastering Laboratory Skills 89

FIGURE 5-20:

Use the edge of a file to notch the glass tubing

FIGURE 5-21:

Place both thumbs near the notch and snap the glass tubing

FIGURE 5-22: Rotate the end of the glass tubing in the
flame to smooth the edges

2. you heat the tubing, apply extremely gentle bending As
   pressure on it continuously. When you feel that the
   tubing is near the point that it can be bent, stop applying
   pressure. Continue rotating and heating the tubing for
   few seconds longer. (If you heat the tubing to the point
   where it begins to sag under its own weight, you’ve gone
   much too far.)


3. Remove the tubing from the flame and allow it to cool for
   a couple of seconds, keeping it straight.


4. Using one smooth motion, quickly bend the tubing
   gently to the desired angle. Hold the tubing in position
   for several more seconds until it hardens and then set it
   aside on a heat-resistant surface to cool completely.

FIGURE 5-23: Heat the section of the glass tubing to be

bent by rotating it in the flame

A good bend is one in which the tubing assumes the desired angle

smoothly with no internal crimping or constriction. If you haven’t

heated the tubing sufficiently, the bend will be uneven. If you’ve

overheated the tubing, the bend may be too sharp and there may

be a constriction or blockage at the most extreme part of the bend.

Drawing glass tubing requires the same initial steps as bending

it. To draw tubing, heat the tubing until it is pliable and then pull

the two ends straight away from each other until the heated

section of the tubing is drawn down to the desired size. Cut the

tubing in the middle of the drawn section and fire-polish the

ends. Figure 5-24 shows a section of tubing that has been drawn

to a fine point.