Cooling baths for demonstrations and experiments come in a number of configurations. This is the ingredient in commercial cold packs. Keep a saturated NaCl solution in stock.
More particles produce a larger freezing point depression.
Add the dry ice slowly to prevent frothing. After setting to our gas, store the acetone in a separate container for reuse. This mixture is best contained in an insulated beaker or Dewar beaker. Use special care to exposure to the skin.