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Thread: Brake Fluid Storage Oddity. Any chemists in here?

  1. #1
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    Brake Fluid Storage Oddity. Any chemists in here?

    After changing out my car's brake fluid, I wanted to store the leftovers for a short time to add if necessary. Because brake fluid is hygroscopic, I attempted to store the partial container of it by slowly flowing CO2 into the top of the container. The CO2, being heaver than air, should have displaced the air which should simply spill out the top. I then sealed the can tightly and left it in my garage overnight. The next day, I found the can crushed, as seen below. Temp at time of sealing was in the mid 80s (F). Overnight temp in the mid 70s (F). Back to the mid 80s (F) the next day.

    • Pentosin DOT 4 LV. Can is steel, 1 liter.
      Estimate about 30% filled with brake fluid.
      Brake fluid chemical makeup:
      Triethyleneglycol monomethylether
      2,2 -(octylimino)bisethanol




    Did I run into an unexpected endothermic reaction?

    Thanks!

    Ken...
    Last edited by kbcons; 07-18-2016 at 10:23 AM. Reason: Edit to fix spelling

  2. #2
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    Is this not just an air pressure event? where the air pressure internally was equal to the temperature outside when poured but when you left it overnight, the pressure of the air on the outside was greater than the internal pressure?

    I'm no chemist but I remember this soda can experience from back in the day that displayed this.

  3. #3
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    Quote Originally Posted by derbo View Post
    Is this not just an air pressure event? where the air pressure internally was equal to the temperature outside when poured but when you left it overnight, the pressure of the air on the outside was greater than the internal pressure?

    I'm no chemist but I remember this soda can experience from back in the day that displayed this.
    I would think you'd need a much larger difference in temp for that to occur here. The soda can experiment usually uses boiling water in the can and then you dump it in ice water to cool it, so ~212F to ~32F.

  4. #4
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    Quote Originally Posted by BMWCurves View Post
    I would think you'd need a much larger difference in temp for that to occur here. The soda can experiment usually uses boiling water in the can and then you dump it in ice water to cool it, so ~212F to ~32F.
    Good point. I didn't remember the experiment that well and that was the only thing that came to mind.


    -Sent from a fancy smartphone

  5. #5
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    I detected no odd temperature when handling the crushed can, even when the internal pressure was still low and working on the can. So obviously an air pressure event, but not one caused by a temp differential.

    Ken...

  6. #6
    In toggling between CO2, N, and O in these charts, there are some differences in factors #16 & #17 that appear to be noteworthy and could explain why the can collapsed overnight with room temperature changes. Also, was the brake fluid warmer than room temperature when it was poured into the can?

    http://www.apithailand.com/data.html

  7. #7
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    I think wstr75 is on the right track of asking the brake fluid temperature. Because if you left the container outside in the sun its not going to be the ambient/environmental temperature. The fluid will be hotter due to the thermal radiation being absorbed from the sun.

    Trying to determine the temperature by hand is not an accurate method of determine the temperature. The reason is the thermal conductivity of the material will help dictate how much heat will be transferred. This is just of a perception of what you call "hot". An example of touching a piece of plastic and metal at 100 F. The metal component will perceive to be "hotter" than the plastic piece.

  8. #8
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    Quote Originally Posted by FungShui View Post
    I think wstr75 is on the right track of asking the brake fluid temperature. Because if you left the container outside in the sun its not going to be the ambient/environmental temperature. The fluid will be hotter due to the thermal radiation being absorbed from the sun.
    The fluid had been in a Motive Products power bleeder - basically a translucent white plastic container - sitting in open shade under the hood of the car with a dead cold engine. Ambient temperature was around 85F and there was a slight breeze. The fluid was then transferred back into the can which was also in open shade at the same ambient temp. The CO2 that was flowed into the can was cooler than ambient, though not cold by any measure. The steel of the can should be a pretty good thermal conductor, even for a gaseous product, but I didn't detect any difference once the CO2 was in the can and the top back on. The garage probably cooled to the mid 70s F overnight.

    Trying to determine the temperature by hand is not an accurate method of determine the temperature. The reason is the thermal conductivity of the material will help dictate how much heat will be transferred. This is just of a perception of what you call "hot". An example of touching a piece of plastic and metal at 100 F. The metal component will perceive to be "hotter" than the plastic piece.
    I agree completely. It's just that I'm really having trouble getting my head wrapped around how much vacuum it would take to crush a strong steel vessel. I know Mythbusters did a tank car, but they had to damage the tank to get it to collapse under 23 inches of mercury. There was no damage to this can prior to its collapse.

    Ken...

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