Can we replace helium?

When I was a child it was only available once a year on the Freimarkt, today you can find it almost everywhere: the helium-filled balloon that you can also let fly. (Dear balloonists, I know: a balloon "travels". Even if I am personally convinced that it is actually floating.)

Besides helium, there are a few other gases that are lighter than air and therefore could at least theoretically be considered for a flying balloon. Air and all gases that are lighter than air are listed in the following table, with their carrying capacity m_tr and their density rho (each in g / L at 1013 mbar and 20 ° C):
Gas m_Tr Remarks rho -------------------------- Hydrogen 1.12 combustible material 0.084 ------------ -------------- Helium 1.04 expensive, in trade 0.166 -------------------------- Neon 0.37 0.839 -------------------------- Methane 0.54 combustible 0.668 -------------- ------------ Ammo 0.49 toxic niak 0.719 water soluble flammable -------------------------- Acety- 0.119 flammable len 1.086 ----------------- --------- Ethylene 0.035 flammable 1.170 -------------------------- Nitrogen 0.035 substance 1.170 ------ -------------------- CO 0.035 toxic 1.170 flammable ------------------------- - Air 0.26 100 ° C 0.946 -------------------------- Air 0.00 g 1.205 g / l ------ -------------------- By the way - water vapor is also lighter than air (about as light as ammonia)! However, at normal ambient temperatures, water vapor is not more than a few percent stable in the air, otherwise it condenses into water (fog). And water or fog are then heavier than air again.

Hydrogen and helium are the most suitable balloon gases. Helium is safer because it is non-flammable, but it must be purchased commercially. For small parties there are small pressurized cans for a few balloons at acceptable prices. Qualified persons can generate hydrogen themselves, taking the necessary safety measures into account.

Like helium, neon must be purchased commercially. Since it is not normally sold in small quantities, its use as balloon gas is only considered if it is needed for other purposes and is therefore available anyway.

Methane is the main component of natural gas. However, this usually contains larger amounts of carbon dioxide and is therefore considerably heavier than methane. In addition, we strongly advise against fumbling with the natural gas connections in order to tap something for a balloon filling! (Usually there is not enough pressure to inflate a balloon anyway.)

Ammonia as a balloon gas has considerable disadvantages: it is poisonous and must therefore be handled with particular care, and it is also very easily soluble in water, so that even small amounts of moisture in the balloon can absorb a considerable part of the ammonia and thus reduce the load.

Nitrogen, carbon monoxide, ethylene and acetylene are only a little lighter than air and are therefore practically out of the question as balloon gases. Carbon monoxide is also very toxic. Acetylene and ethylene, possibly also methane, should escape very quickly through the balloon rubber.

Practically all other gases are heavier than air and therefore cannot carry a balloon. In particular, propane, carbon dioxide, butane or argon can be safely forgotten as balloon filling, even if in various novels a balloon filled with propane gas or carbon dioxide rises into the air from time to time.

The buoyancy must be enough to carry the balloon itself, the string on it and everything that you want to give the balloon (e.g. a piece of paper). A balloon with 3 liters of helium in it

3 liters of helium x 1.04 g / L carrying capacity = 3.12 g

can lift a maximum of 3.12 g in total. The balloon shouldn't just float, it should rise, so everything together has to weigh less! In this case about 2.5 g at most.

If you have enough gas, the best thing to do is to use a large balloon that weighs little more than a small one, but it can hold a lot more gas.

The balloon should not be fully inflated because the gas in it will expand as it floats high in the air, where the air pressure is lower. If it was close to bursting below, then this is guaranteed to happen further up. So fill the balloon only half or three quarters at the most.

By the way, anyone who wants to fly a balloon needs a permit in Germany. But if you apply for it properly at the regulatory office, you will usually get it.