Chemistry Practicals For Class IX (Science Group) - Experiment No. 1: To cut and bend a glass tube and draw a Jet.

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EXPERIMENT NO. 1

TO CUT AND BEND A GLASS TUBE AND DRAW A JET

APPARATUS:

• Glass Tube
• Small Triangular file
• Knife
• Match Box
• Meter stick
• Glass marking pencil
• Bunsen burner / Spirit lamp

CUTTING OF A GLASS TUBE

METHOD:

• Place a glass tube horizontally on a table (or any solid support) as given in the figure.
• Measure the desired length by the meter stick.
• Mark the length with a glass marking pencil.
• Make a single sharp transverse scratch with a triangle file at the mark.
• Hold the tube with both hands in a way that thumbs remain below (opposite to) the mark.
• Exert a little force to break the tube into two pieces with a quick jerk.
• Keep the tube away from your face.
• The tube breaks evenly at the scratched place.
• Round the rough edges of cut tubes by rotating in flame (fire-glazing).
• Allow the tube to cool by placing it over an asbestos sheet.

BENDING OF A GLASS TUBE

METHOD:

• Hold a tube horizontally in your both hands over a Bunsen flame at the ptace where it is to be bent as shown in the figure.
• By rolling and moving the tube back and forth, heat the 2 inches part of the tube evenly, that has to be bent.
• Keep it rotating until it softens.
• When glass becomes soft.
• Bend it at the desired angle, keeping it a bit up from the tip of the flame.
• Hold until the glass hardens.

MAKING OUT A JET

METHOD:

• Hold the tube in your both hands as given in the figure.
• Put it over the flame in a way that only one and half inch of the tube remains in the flame.
• Slowly rotate the tube about its axis, keeping it in the flame until it softens.
• When soft, remove it from the flame and immediately draw the two ends apart carefully till it forms a fine capillary of desired diameter.
• After cooling, cut the tube to separate the two ends by means of a knife.
• Round the rough edges of cut tubes by rotating in flame (fire-glazing).
• Each piece of the tube has a jet.

PRECAUTIONS:

• The scratch on the tubes should be sufficiently deep.
• Pressing of thumbs should be with a uniform force.
• Avoid too much heating, it may cause poor bends.
• The tube should be continuously rotated while heating.
• Do not keep the hot tube on the table.
• Pull the ends of the tube by taking it out of the flame.
• Heat the tube in the upper portion of the flame and continue rotating.
• While drawing a jet the pulling apart of the glass tube should be immediate and carefully.
• Never try to break the tube with simple bare hands.

Special Thanks to Sir Sajjad Akber Chandio