This is a highly
mature device, popular with
schoolchildren
The 'Bomb Bag' is a 4 inch square foil bag, sealed so as to be airtight. Inside is a large quantity of
baking soda, and a sachet of
acid and
water.
To use a bomb bag:
- Probe the bag until you locate the sachet
- Squeeze the sachet so as to burst it
- Secrete the 'Bomb Bag' upon someone else's person (Their bag is good, but a pocket is even better1)
- Retire to a safe distance
Once the sachet is popped, the acid begins to react with the baking soda, forming carbon dioxide and water (and a
salt).
For example, a 'Bomb Bag' that uses
citric acid:
3NaHCO3 (Baking soda) + C6O7H6 (citric acid) -> Na3C6O7H (sodium citrate (the salt)) + 3CO2 (Carbon dioxide) + 3H2O (water)
The carbon dioxide formed causes the pressure inside the bag to rise, until the bag bursts, creating a loud noise, and spraying foamy water everywhere. To the annoyance of the
person it's planted on. Bomb Bags can be had for about 10p in any good
joke shop.
1 - When I was at school, our school uniform included a blazer which had pockets exactly the right size to conceal 'Bomb Bags', either a supply of undeployed bags, or a single deployed one.