The use of gas bags for the storage and handling of
is well over 200 years old. Henry Cavendish described the
of a “bladder” for gas manipulation in his 1766 publication On
Airs (Figure 1) and Carl Scheele used the a large gas bag when he
“fire air” (oxygen) in 1772.(A Short
of Chemistry, J. R. Partington, 3rd edition, (1957)) (Figure 2)
Figure 1. Gas bladder used by Henry Cavendish
Figure 2. Gas bladder used
A century later, gas bags
still common. In the 1872 text by Storer and Lindsay,(An Elementary Manual of Chemistry, F. H. Storer
W. B. Lindsay, American Book Company, 1872.) a gas bag was used to make a
of soapy bubbles containing a hydrogen-oxygen mixture (Figure 3).
Figure 3. A 19th century gas bag experiment
And now, another century later, gas bags are still used, although
has replaced animal organs. Courneya and McDonald described the use of
plastic bag to store gases in 1978.(Courneya,
D and McDonald, H; The Science Teacher 45(6), 43, September 1978.
article is reprinted in Irwin Talesnick’s Idea Bank Collation, A
for Science Teachers, Volume 1; 1984, Part Number CB 066, S17 Science
and Services. Link to the S17 website is provided at our microscale gas
A modification of this can
be purchased from S17 Science Supplies and Services.(Part Number EQ 059, S17 Science Supplies and
In this chapter we describe the use of 1 L (1 qt)
food storage bags such as Ziploc‚ bags for transferring gases and
storing gases. The gas bag can be used to fill syringes for use
students. One gas bag will fill at least twenty 60 mL
The technique is exceedingly convenient in situations such as
a mechanical or welding shop
obtaining helium from a
or flower shop
collecting natural gas
has enough pressure to inflate a bag but not enough to push a plunger
preparing large quantities
a gas such as carbon dioxide, hydrogen or oxygen (inside the 1 L bag)
use in multiple experiments
discharging a gas such as
H2 or CO at a constant, controlled rate
order to sustain a small flame.
Basic materials needed
60 mL plastic
1 L (qt) freezer-quality
storage bag, for example, Ziploc
tubing, 1/8 inch (3.175
ID, 15 cm length
plastic hemostat or pinch
The use of gas bags is intended for use by
Gas bags can save time and provide a useful method for delivering
quantities of gas at a constant flow rate.
Construction of the gas bag from a food storage bag
Use a pencil or similar round, sharp object to poke
hole through the plastic bag in a position similar to that shown in
4. Moisten one end of the piece of tubing with dish soap in order
facilitate pushing it through the hole in the bag. The gas bag is
ready for testing. Fill a large pail (10 L) with water.
the gas bag with air. Hold the point of connection between the gas bag and the tubing under the
and check for leaks (or place some water in the bag and let it pool
the tubing and then check for leaks on the outside of the bag).
found that there are seldom leaks. The seal, however, often leaks
slowly, but in most cases slow leaks are of little consequence.
Figure 4. A 1 L Gas Bag
Possible uses for the gas bag
1. The gas bag is a time-saving device when used as a large reservoir
fill syringes for use in microscale gas experiments by students.
2. Use the gas bag to transfer oxygen from a mechanical or welding shop
the lab. Connect the tubing from the gas directly to the cylinder
compressed oxygen. Squeeze all of the air out of the bag before
to the cylinder. After the bag is full, clamp the tubing shut
the hemostat or pinch clamp. Avoid overfilling the gas bag.
3. Use the gas bag to transfer helium for from a grocery or flower
Same instructions as above, however it is also possible to buy a helium
from a store (not overfilled) and transfer the gas from the balloon to
bag: Near the mouthpiece, but 3 cm away from the knot, twist the
to make a new temporary seal. Cut a small slit (2 mm) with a
between the twist and the knot. Work the tubing into the hole
soap, as before). Open the hemostat and slowly release the twist
Gas will start filling the gas bag. (We have used helium in the
mass experiment (Chapter 6), but better results are obtained with gases
large molar masses.)
4. Use the gas bag to collect natural gas or propane. These gases
enough pressure to inflate a gas bag but not enough to push a plunger
Simply connect the tubing to the gas jet. For propane from a
torch tank, remove the nozzle from the propane torch and slip rubber
of suitable diameter over the brass fitting on the torch. The
can be “reduced” in diameter by slipping it over a smaller diameter
of tubing connected to the gas bag. Use tape to achieve an air-tight
if necessary. Gas bags filled with flammable gases should be in
custody of the teacher at all times.
5. Use the gas bag to prepare large quantities of a gas such as carbon
oxygen or hydrogen.
o Carbon dioxide: Place 3 g NaHCO3 inside
gas bag. Squeeze out most of the air, zip the bag shut and remove
remaining air by withdrawing it via the tubing using a 60 mL
Use a 60 mL syringe to transfer 50 mL of vinegar to the bag. The
will commence upon contact between the two reagents. After the
is complete, samples of CO2 can be
for various experiments.
o Hydrogen is prepared in a similar fashion using 1 g powdered
(inside the bag) and 50 mL 1.2 M HCl(aq) admitted via the tubing.
reaction becomes quite warm and is complete within one minute.
forms of magnesium (turnings, ribbon) also can be used.
o Oxygen is prepared using 0.5 potassium iodide (inside the bag) and 60
admitted via the tubing. The reaction is considerably slower; it
about 5 minutes.
v Use the gas bag to discharge a gas such as CH4,
H2 or CO at a constant, controlled rate
order to sustain a small flame. Assemble the apparatus as shown in
5. Use a 15 cm length of tubing to connect the gas bag to a glass
(The tubing will form a snug fit inside the pipet.) Keep the gas bag
from flames. Open the pinch clamp and ignite the gas issuing from
pipet. Gently press down on the gas bag to control and sustain the
To stop the combustion, pinch the tubing shut.
Figure 5. The gas bag being used to discharge a flammable gas at
Figure 6. The gas bag used to generate strange musical sounds.
Combustion of hydrogen in oxygen demonstration. A flask as a
Generate oxygen and hydrogen in separate gas bags
label them. Fill a 250 mL Erlenmeyer flask with oxygen from the
bag and stopper it until needed. Refer to Figure 6 for a pictorial
of the apparatus and procedure: Connect the hydrogen gas bag’s
to a 5 mm OD, 15 cm piece of glass (a pipet will not work) held in
with the aid of a ring stand and clamp as per the figure. Keep
gas bags away from flames. Remove the clamp/hemostat and
ignite the hydrogen issuing from the glass tubing. If necessary,
press down on the gas bag to control and sustain the flame. Slip
flask of oxygen over the burning hydrogen and move the flask over the
glass tube. As the glass tube/flame moves deeper into the flask, the
will drop. Move the flask “on and off” to cause the pitch to
The flask will become hot. To stop the combustion, remove the
and pinch the tubing shut. Note the water vapor in the flask!
View a QuickTime video of this musical demonstration.