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How do I turn sodium acetate trihydrate into sodium acetate anhydrous and vice versa?

  1. May 27, 2012 #1
    I just made some sodium acetate trihydrate at home and I would like to make it into sodium acetate anhydrous. Sorry if this is a stupid question but I am new to chemistry and I love it.
  2. jcsd
  3. May 28, 2012 #2
    Re: How do I turn sodium acetate trihydrate into sodium acetate anhydrous and vice ve

    If you fuse (i.e melt) the hydrated sodium acetate, you may be able to boil away the the waters of hydration at temperatures well above the melt temp.

    The anhydrous salt according to Wiki has a melt point of 324C vs the trihydrate of 58C. additionally Wiki has the decomposition (i.e loss of water) of the trihydrate at 122C. Some temperature between 122C and 324C would ensure making the anhydrous salt.

    If you can get some drying agent (anhydrous CaCl2- purchased as DampRid here in the US for households at most hardware stores), you can make a mason jar drying chamber or a coffee can drying chamber. Put the drying agent in the bottom of the jar or can, and put a mesh or layer of cotton and a screen above it to protect your weighing dish of salt. It should be closed and the system will equilibrate (faster if warmed). The crystals will start to look like they are breaking down to a powder as the water is lost. The transition should be faster if warmed to the melting point of the trihydrate and done from the melt, but your weighing dish must be non corrosive- i.e don't use aluminum !

    You can do the stoichiometry and determine how much theoretical weight loss to expect in either case. Dry in the drying chamber until a constant weight is obtained.

    Your anhydrous sodium acetate will pick up water from moist air readily (deliquescent) so the reversion back to trihydrate can be done by making the reverse of the drying chamber where a little water is at the bottom of the chamber (moisten some paper towels or cotton and crumple in the bottom- make sure to place a screen that supports your dish above the wet towels or cotton).

    Good luck in your observations!
    Last edited: May 28, 2012
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