Page 13 - Chemistry - XI

Q4. Why should we draw lines on asbestos sheet?
Ans. It helps in bending the glass tube at the exact angle which is required.

Q5. Why is sudden cooling of the hot part of the glass tube not advisable?
Ans. It may break on sudden cooling.

EXPERIMENT - 3

Objective
To draw out a glass jet.

Materials Required

Glass tubing, burner, asbestos sheet, triangular fi le, and sand paper

Procedure
1. Take a glass tube of about 30 cm long.
2. Round off the edges of the tube.

3. Hold the tube horizontally.
4. Heat the glass tube in the middle by holding the tube on both sides.
5. Rotate the tube slowly until the portion which is kept on the fl ame becomes red hot and soft.
6. Remove the tube from the fl ame and pull the ends apart slowly and smoothly until the centre has
become narrow and then stretch into a fi ne jet.

7. Cut the tube from the middle with the help of a triangular fi le and make the jet uniform.
8. Smooth the ends by rubbing with sand paper and by fi re polishing.

Heat the tube in the Bunsen Flame while Continue Heating and Rotating with inward
rotating between fi ngers pressure till the tube in the centre becomes soft.

Cut to length and round off the two ends
Remove the tube from the fl ame and after a smooth by sand paper and fi re polishing
moment pull the ends apart to get the narrow
capillary in the middle.

Fig. 3.1

Precautions

1. Do not heat glass tube at one point. Keep on rotating the tube.
2. Keep your face away while fi lling and breaking the glass tube.
3. While drawing out a jet, the pulling of the two ends of the red hot glass tube should be done slowly.While drawing out a jet, the pulling of the two ends of the red hot glass tube should be done slowly.

11