Ever read about the effects of helium on your voice? Ever wondered if it is possible to go from a high-pitched Bee-Gee-style squeak to Darth Vader mode by using krypton? Well, it is possible - in principle. There are some downsides to this experiment, when compared with the helium experiment linked to above. Firstly, krypton is not as broadly available as helium, and it is a lot more expensive. Secondly, the pitch won't go as marked as helium, it will just go less than one octave lower. It's also (as with helium) a bit dangerous.

The Science Bit

In the aforementioned helium entry it is shown that inhalation of helium can cause your voice to go more than one octave higher than its normal tone. The reason for that is that the speed of sound, and hence its pitch, is a function of the density of the gas it is moving in. In more correct terms, the speed of sound (v) for a gas is directly proportional to the root of the inverse density (d):

v = (p · c_p / c_V · d)^½

In this formula the pressure (p), the heat capacities at constant pressure and volume (c_p and c_V) can be seen as constants. In other words, the higher the density, the lower the pitch. The velocity of sound in a denser-than-air gas, such as krypton, is about 200m/s. The speed of sound in air is about 330m/s, therefore the frequency of sound in krypton is almost 0.6 times lower than the frequency in air, or not entirely one octave lower. A normal man's voice will sound like the Star Wars character Darth Vader.

The Risks

Chemically, krypton is inert. It is therefore not going to do anything 'evil' to one's lungs; it is not going to burn, cause cancer or anything else. However, since it is somewhat denser than air it can almost be thought of as a very thin liquid. It will sink to the bottom of your lungs and stay there, displacing necessary oxygen. While one could effectively 'drown' in such a gas it is not too difficult to exhale the gas properly. Inhaling krypton is a bit like fire breathing - dangerous, but then again you see it being done on TV, or in lecture halls. So here is some basic advice:

• Remember good breathing techniques and exhale properly
• Never do this alone, seek qualified assistance if possible
• Don't do it in a cupboard, make sure the room is ventilated

Further Warnings

There are even denser gases than krypton. Trying to lower the pitch of your voice even further with these gases, however, can be significantly more dangerous, as the gas might be reactive and harm the lung and the risk of 'drowning' in such a gas is increased.

Avoid inhaling any gas directly from the outlet (there may be sharp metal splinters or harmful lubricators in the innards of a gas container). Inflate a balloon instead.