Dust explosions using cornflour, custard powder,

From TecHKnow Wiki
Jump to navigation Jump to search
Coffeecansm.jpg

Apparatus

  • One catering size coffee can (or similar design). A plastic lid will work!
  • Three tea lights.
  • Approx. 80mm glass tubing#
  • Approx. 0.5 m pvc tubing#, which fits over the glass tubing.
  • Balloon pump. Or other means of making the dust airborne.
  • Suitable powder1,6
  • Utility lighter / splint
#The length of glass tubing should be such that, when inserted, it doesn't protrude too far 
on the outside of the can (this will depend on the size of the can). Longer tubing may make
it easier to retreat behind the screen and should have no obvious side effects.

Safety

See CLEAPSS supplementary risk assessment SRA 0244.
Also safety tip when you see this sign. Caution.jpg

Method

  • Cut a suitable length of glass tubing. There should be a minimum of glass tubing protruding outside the can, this allows the pvc tubing to keep the glass tube stable.
  • Flame the ends of the glass** to smooth them.

Flame.jpg

  • Bend one end of the tubing3 to an angle of approx.

Gtb.jpg

  • Double check the o.d. of the tubing.

Measure.jpg

This will correspond to the size of drill bit. It may help to place two pieces of blu-tac 
on the bench to hold the can.

Btcd.jpg

  • Drill a hole 1/3 of the way up, from the base.

Right

  • Insert the glass tubing through the hole from the inside of the can. Blu-tac can be used to seal any gap around the hole.
  • Place one end of the pvc tubing over the glass tubing. It may help to soften the tubing with a small flame (briefly) or beaker of hot water.

Caution.jpgUse a pair of strong gloves incase the glass tubing breaks.

Shortglass.jpg

If there is too much glass tubing protruding, then the end will move when the pump is 
moved. Thus not remaining on the watchglass. A possible bug, as it is impossible to see 
this happening with the lid on!

Glasslong.jpg

In this case 6mm O.D. (0.7mm wall) glass tubing was used.  Also 5mm I.D., 8mm O.D. 
pvc  tubing.  The I.D. of the pump is also 8mm, but can accommodate 10mm I.D., and 
possibly larger?

Setup.jpg

  • Fill the base of the can with sand up to the level of end the glass tube.
  • Place a watch glass under the end of the glass tube.
  • Position the three candles around the tin, if one goes out the others should stay lit5.

Can.jpg

Caution.jpgPlace the powder on the watch glass before lighting the candles.

TIP!! Custard powder needs to be dry. Place some in an evaporating basin and leave in an 
oven at about 100C for at least an hour. Take it out just before you need it 
(warn the teacher that the basin is hot !).
  • Retract the plunger of the pump before connecting it to the pvc tubing
  • Put the lid on and retreat behind the safety screen. Then push the plunger.

Aside from CLEAPSS SRA, these instructions need not be followed exactly: if it works it works.

Please read the risk assessment4 and the theory of the demonstration1


External Links

1 http://www.chem.leeds.ac.uk/delights/texts/expt_6.html

2 http://www.teralab.co.uk/Glass_Blowing/Cutting_Tubes/Cutting_Tubes_Page1.htm

3 http://www.ul.ie/~childsp/CinA/Issue65/TOC26_ChemTips3.htm

4 http://www.cleapss.org.uk/publications/secure/SRA/SRA%2002%20Dust%20explosion.pdf Also on the latest cd-rom. (Need to be a member to access this area of the website)

5 http://www.sciencetechnician.com/forums/topic.asp?TOPIC_ID=821

6 http://www.sciencetechnician.com/forums/topic.asp?TOPIC_ID=332

http://www.chemeng.ed.ac.uk/~emju49/SP2001/webpage/


--Aclearn 09:34, 2 March 2007 (GMT)


* Return to: Laboratory Experiments


This contributor(s) article

Help us improve TecHKnow Wiki