The Gas Blanket Myth

“Oxidation of Wine can be significantly delayed by a “blanket” of inert gas.”

The Heavy Gas Myth

“Argon makes a better “blanket” since it is heavier than Nitrogen.”

Referring to the “Ideal Gas Law”,[1] there is no difference in the actions of different kinds of gas particles, and they all are at the same temperature and so are moving with the same energy.   The particles of Argon, being heavier than the two-atom Nitrogen particles, will move more slowly than the Nitrogen particle by a factor which is the square root of the ratio of the mass of Nitrogen gas particle to the mass of the Argon atom.   

Nitrogen is a diatomic gas, two atoms to a gas particle, where Argon is a mono-atomic gas, so the slower velocity of the Argon particle differs from the Nitrogen gas particle velocity by the square root of 28/40, which is  0.836, not a large velocity difference anyway.

But much more important is the theory of gas diffusion first put forth in 1833, developed by Thomas Graham   (Source of Graham’s Law) and the main phenomenon was described by him as follows:[2]

“…gases of different nature, when brought into contact, do not arrange themselves according to their density, the heaviest undermost, and the lighter uppermost, but they spontaneously diffuse, mutually and equally, through each other, and so remain in the intimate state of mixture for any length of time.”

This says that gases can never form a “blanket”, and Ends both the “Heavy Gas Myth”, and the “Gas Blanket Myth”.

 

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[1]Gas Law Details:

The physical “Law” for Gasses, called the “Ideal Gas Law” where Ideal refers to the Gas, not the Law, involves 4 very well-proven assumptions, so well-proven that they are nearly axioms.  The assumptions are:

  • Any gas is made up of particles. Atoms, Paired Atoms, aka Molecules, and lots of other molecules, and all the particles are in constant motion.
  • There are no attractions or repulsions between the particles; collisions between like and unlike particles are like billiard ball collisions.
  • There is a lot of space between the particles compared to the size of the particles themselves.
  • The speed of the particles increases with increasing Temperature.

As the particles, atoms or molecules of gas, collide with the walls of their container, they exert a force on the walls.  The average force per unit area is the Pressure of the gas.

The speed of the particles is related to the Temperature.  The greater the speed the greater the Temperature.  At any given temperature the velocities of the particles differ by the square root of their masses. Lighter molecules moving faster than heavier gas particles.

The walls of the container define the Volume of the gas.

Avogadro got things started by showing that the weight of a volume of a gas in 22.4 liters of space is equal to the atomic or molecular weight of the gas in grams. Some years later the number of atoms in the volume was computed to be 6.022 x 1023, and to honor Avogadro that number was named for him.

Boyle demonstrated that for a constant Temperature the product of the Pressure and the Volume is constant:                                                                                          PV = Constant, if T is constant

Charles showed that     V/T = Constant, if P is constant

Dalton put it together:    PV=NRT    where N is equal to the sum of all the gas particles in the Volume, or:                                                                                                      PV = RT x (N1+N2+N3. . . .)

 

[2]  Diffusion Processes, Thomas Graham Symposium, ed. J.N. Sherwood, A.V. Chadwick, W.M. Muir, F.L. Swinton, Gordon and Breach, London, 1971.