Celebrating 20 years of Homebrewing January, 1997 Volume 20, Issue 1

Beer Gas

Compiled from e-mails on Home Brewers’ Digest

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Nitrogen/carbon dioxide mix was the topic of a Zymurgy article by Cliff Tannor in Summer of 1994.

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Don't expect to take your CO₂ tank in and get it filled with CO₂/N₂ mix ("beer gas"). This is the result of safety. Each type of cylinder has different threads (male/female, right/left hand, thread pitch) so people can't put an oxygen regulator on a hydrogen tank. Most CO₂ tanks have CGA 320 fitting.

Pure CO₂ is a liquid in a cylinder. Some small research grade cylinders are at lower pressures, and as a result are just gas.

A dip tube is used any time you want to deliver a liquid compressed gas - quite simply it takes the liquid off of the bottom - You can buy tanks to provide liquid CO₂ that come with the dip tube, without the dip tube you get gas (from the tank, that is).

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If the mixed gas were dispensed from the top, the concentration would not be constant as a result of the different vapor pressures of the two compounds. The normal boiling points (i.e., pressure where vapor pressure=1 atm) are -78.2 for CO₂ and -195.8 for N₂ (Centigrade), so the gas in the head space would be primarily N₂ at the beginning and primarily CO₂ at the end.

I'm a little surprised to hear that the mixed gas is liquefied - I didn't think that regulators could work on a liquid input and produce a vapor output. Obviously, it would have to be a different style of regulator than the "normal" type used for compressed gases.

I have contacted my supplier and am having a batch of 63/37 % made up for me. The delivery guy for Linweld has stated in the past that only the 73/27 was available, but that is only due to it being the blend of choice for those with Guinness on tap. They are more than happy to make any blend requested, they just don't have it in stock.

My current tanks are known in 'Lindy' nomenclature as an "S" size cylinder. Scott calls it the same. In Mattheson terms, it's a "Number 3" cylinder. Others call it a "KA" cylinder. It stands 52 Inches tall, inclusive of valve cover. The Liquid Gas Association(?) apparently has no standard nomenclature for cylinder sizes. The label states, "444,021 liter capacity." When ordering the 1st proposed 50/50, Mark at Linweld stated that they thought they could only get 120 cu. feet in, whereas the expectation is 142 cu' for my 73/27. But today the picture is brighter, they expect, through improved filling techniques to get 144 cu' in the new blend. The cost--I should have looked it up for you, but $30?..$33? It isn't that expensive.

I asked about the dip tube and the question on liquid state gas versus gaseous state. He said that the dip tube may or may not be present, but that all the presence or lack thereof influenced was the filling procedure. On a tank with a dip tube you fill the heavier product (CO₂) first, then the lighter product (N₂). On a tank without a dip tube, you do the opposite. He indicated that this was somewhat of a universal concept amongst refillers when gases of different weights are introduced.