I have access to dry ice (CO2) and I have a vacu-sealer. I'd like to put away large bags (25 to 50lbs) of sugar, rice, and several different beans in Rubbermade totes. Is one method better than another?
Thanks,
M

Keep in mind CO2 is not N2, which is an inert gas used for storage.

Dry ice will expand when converting to CO2 gas, so be care whenever placing dry ice in a sealed container.

N2 will not support the growth of microorganisms, whereas CO2 may support the growth of certain microorganisms.

Pete

Can you use liquid nitrogen for charging a container (and its contents) with N2? Is there a "best way" to insure that N2 has replaced the ambient air? Is N2 heavier than air? I planned to seal the containers with silicone glue or caulk. Is that appropriate?
Thanks again,
M

This sounds like a "Blast-thing". However, since he's out doing water survival against bathing cats for his show I would recommend at least looking up the element numbers on the Periodic Table for oxygen and nitrogen. Nitrogen is a component of air. It is lighter than Oxygen. N=14, O=15.99

Liquid nitrogen is tricky stuff.

Caveat...I'm probably full of hot air myself.

I think you may not need to worry about purging all of the other gases from a container. If you purge a lot of the O2 then you will have some effect, and anything that uses the O2 will use up the little that you have left rather quickly.

Of the gases in air, I think, nitrogen is one of the lighter ones, so you may want to add the N2 to an atmosphere when the N2 is warm. Liquid N2 might not do what you want it to do.

Nitrogen is more than 70% of the air, and oxygen makes up about 21% of air, followed by argon, CO2, neon, helium, methane, krypton, nitrogen oxide N2O, and hydrogen. I am pretty sure all but the hyrodgen and helium are heavier than nitrogen.

If you were trying to change the atmosphere in a tank with air in the atmosphere, you would push nitrogen into the top of the environment, and let gas escape from the bottom. Using an 02 sensor, you should be able to tell when the N2 had evacuated the O2 and thus all the air.

I think if you are going to seal things at that point, you want to do it quick, so the glue or caulk may not be a good idea.


EDIT:

I was looking for information on how LNG or similar ships change atmospheres, but could not find any. Generally, they push lighter gases into the tops of tanks and heavier into the bottom and the do so slowly. If you do it too quickly, the gases will mix, and diluting an atmosphere takes longer than just a change. Also, beware of pushing warmer gases into the bottom or colder into the top of anything, and the temperature difference leads to mixing or maybe the gases flipping. Been a while since I looked at the loaidng manual for any ship like this.

I think it would be easier to use dry ice (carbon dioxide) than liquid nitrogen.

You can purchase O2 indicators (turn pink in the presence of O2 and are colorless in the absence of O2) to help you determine when atmospheric air has been purged from whatever you are gassing.

As to liquid N2, I really do not know how well that would work, as is would freeze any item with which it comes into direct contact. If you had it in an open container within the container, which you wish to purge and seal it might work, but you could not seal the container until it, all of the N2 enter the gaseous phase, otherwise you run the risk of an explosion. Be very careful with N2, it can cause some very nasty burns, full thermal (long gloves, apron and foot wear designed for use with liquid N2) and eye protection are required to prevent splash injuries. Likely better off with a cylinder of N2 gas for this application.

Pete

What are you putting the foods into, directly? I don't believe that the Rubbermaid totes that you are using are really suitable for food (food-safe). I think it would be better to seal the foods in those mylar bags, then put the bags in the totes.

If you know any Mormons (Latter-day Saints), ask them. They probably know more about this subject than any other group.

Sue

Thanks for all the responses. I was planning to buy bags of the various food stuffs and then put them into the 18 gallon Rubbermade Toughneck containers, purge the O2, seal them and forget about them (not really but put them away). The bags I've seen at Sam's and CostCo are any where from 5lbs to 50lbs. I was thinking that I would get more of the smaller bags; say 2 of the 25lb verses the 1 50lb. That way when I do rotate them (in 4 years or so) they will be more convenient to use.
Thanks for the advice Susan. I did ask a guy at work who I heard was Mormon; he was a lot more interested in converting me than helping me stock up.

Freinds of mine use CO2 to store food what they do is place about a half a cup of dry ice in the bottom of a food grade 5 gallon bucket cover it with paper towels and put the dry food they want to store on top of the paper towels. Then they put the lid on loosly and allow the dry ice to start melting and displacing the oxygen in the bucket. They then put a lit match in the bucket and if it goes out they put the lid on tight.
My freinds only use the Rubbermaid totes to store dry items that are already in sealed bags, like pasta and stuff like that. All beans, grains, sugar, flour, and similar grains and grain products they seal in buckets.