Cpm 154 Ht?

scottickes said:
Try calling around to grocery store chains and ice cream stands. I moved across country back in 2002, and was able to find dry ice easily at these types of places during the trip to keep my venison frozen!
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Oxygen supply/welding supply places often have it as well
 
awesome all set guys... i got 5lbs from a local dairy place. they're nice people there. we usedto buy our milk bottles there when we were still milking a cow.

they're soaking right now... they dry ice should be all melted soon. then its back in the oven with em. thakns again guys
 
fitzo said:
Dry ice/isopropyl alcohol -78C (-108F) per the Chemist's Companion:

http://www.vanderbilt.edu/AnS/Chemistry/Rizzo/stuff/baths.html
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Fitzo,
Your specifications are with pure, clean dry ice with no water contamination. I've found that dry ice is rarely that pure. The coldest I've ever gotten it was -55 F. I've frozen hundreds of bearings using dry ice with alcohol, anti-freeze and acetone. I've found the average temperature to be at about -45 F. before it sets up and will no longer be slushy.

It goes from slush to solid below certain temperatures, which is based on the variable of the % of water contamination. The most inconsistent dry ice comes from places that handle food, such as grocery stores and ice cream stands. They don't need -108 F., so they aren't real picky about it.

Just my observations from real life experience with the stuff.

Ickie
 
Scott, I used dry ice baths nearly daily for 30 years, so I have a little real life experience, too. I've measured the temp so many times I couldn't begin to count. And if it's not down below -75C it got tossed because we needed those temperatures for chemical reactions. Dry ice- acetone, isoprapanol, methanol. Ethanol was too expensive because it was taxed and we didn't keep adulterated alcohols in the lab so I couldn't speak from experience. We got dry ice once a week in hoppers about the size of 6 large refrigerators and used it all, so our supply stayed fresh. By the end of the week the dregs had frozen a lot of moisture from the air onto it, so I can understand where your impressions come from.

I feel bad for the quality of dry ice you can find. It's dry ice in name only at that point. If it's got so much water that it slushes at -45F that has to be about the crappiest dry ice I have ever heard of. We tended to throw it out if a lot of clear spots showed, because that's water. That's not even really a dry ice/solvent bath anymore when that much water is introduced if it "sets up" at those temperatures, but a dry ice/water/ solvent bath which obviously has much different properties. (A "GOOD dry ice"/alcohol bath will be viscous but the liquid won't be frozen at -108F.) That said, even the stuff I have bought from the catering place or for transporting fish has never been bad like that. So, I agree, you are getting some heavily contaminated crap.

Not worth arguing about.
 
fitzo said:
Scott, I used dry ice baths nearly daily for 30 years, so I have a little real life experience, too. I've measured the temp so many times I couldn't begin to count. And if it's not down below -75C it got tossed because we needed those temperatures for chemical reactions. Dry ice- acetone, isoprapanol, methanol. Ethanol was too expensive because it was taxed and we didn't keep adulterated alcohols in the lab so I couldn't speak from experience. We got dry ice once a week in hoppers about the size of 6 large refrigerators and used it all, so our supply stayed fresh. By the end of the week the dregs had frozen a lot of moisture from the air onto it, so I can understand where your impressions come from.

I feel bad for the quality of dry ice you can find. It's dry ice in name only at that point. If it's got so much water that it slushes at -45F that has to be about the crappiest dry ice I have ever heard of. We tended to throw it out if a lot of clear spots showed, because that's water. That's not even really a dry ice/solvent bath anymore when that much water is introduced if it "sets up" at those temperatures, but a dry ice/water/ solvent bath which obviously has much different properties. (A "GOOD dry ice"/alcohol bath will be viscous but the liquid won't be frozen at -108F.) That said, even the stuff I have bought from the catering place or for transporting fish has never been bad like that. So, I agree, you are getting some heavily contaminated crap.

Not worth arguing about.
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Agreed.

Ickie
 
so i soaked the suckers for about 6 hours... before the ice was gone... and i did not really know i should crush up the ice. so i'm sure i sacrificed some of the temp i could have been getting.
ahh well there's always tomorrow.

so can i use this acetone again? or is it shot? i'm going to see if i can measure the temp this time around. i believe my themocouple for my furnace goes to -300 or so so i can see exactly what i'm at. should be cool to see actual results.

thanks again guys.... these suckers are off to the tempering oven now
 
The acetone should be just fine, Michael....just keep it in a closed container between uses. Eventually it might absorb enough water to slush up or freeze. If that starts happening, dump it.

There's no real scientific need to crush the ice. As long as there's dry ice and the liquid isn't "boiling", it means it's still as cold as it can get.
 
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