Do soft drink machines in food establishments use liquified CO2 or is it in another form?

Hi Wesley: I knew this but here's a quote:

"It is used in many consumer products that require pressurized gas because it is inexpensive and nonflammable, and because it undergoes a phase transition from gas to liquid at room temperature at an attainable pressure of approximately 60 bar (870 psi, 59 atm), allowing far more carbon dioxide to fit in a given container than otherwise would."[1] So at 20 °C and ~60 atm pressure CO2 is a liquid [see phase diagram on left in ref [1]) and fresh cylinders of CO2 in beverage machines almost certainly have liq CO2 in them (the pressure can't go above 60atm). I use to make one of my starting materials under 200 atm CO at RT, 400 atm at 320 °C rxn T so it easy to compress gasses to 100 atm or more.

There is now an extensive switch in industry to use liq or supercritical CO2 as a "green solvent". You carry out the desired rxn under high pressure CO2; after rxn is complete cool and reduce the CO2 to atmospheric: collect and recycle CO2 leaving the product as a solid in a rxn flask (I've seen it done shown on slides and it is amazing). CO2 is cheap and nontoxic. A good example of this use is that the decaffeination of coffee is now carried out by extraction with CO2(l); a process that was previously carried by extraction with CH2Cl2.

Cheers, drp

You cannot get liquified CO2 at normal temperatures. The CO2 used is supplied and stored as a high pressure gas.

Nope, it's gas stored in metal bottles.

In some places they're knee-high and about eight inches across, hand-delivered. Other restaurants have one big CO2 tank, connected to a port outside the building where a delivery truck can plug in and refill the tank.

(Incidentally - it takes a pretty unusual combination of temperature and pressure to get liquid carbon dioxide. At standard pressure, CO2 goes straight from gas to solid - dry ice - and back again.)

The CO2 is compressed (like compressed air). CO2 doesn't really exist as a liquid. Dry ice is frozen CO2, but it sublimates goes directly from solid to gas, no liquid stage intermediate.

Thre really is no such thing as liquifed CO2.

if it WAS used in soft drinks, it would freeze the drink solid, and you couldn't drink it. It would also freeze the skin on your lips, tongue, adn mouth, making it VERY dangerous to drink it.

Any CO2 used in soft drink machines is a compressed gas.