Reaction of sodium carbonate in ethanoic acid. This is an example of an endothermic (heat absorbing) acid-carbonate reaction, which produces a metal salt. Ethanoic, or acetic, acid is a weak acid found in vinegar (here 6% wine vinegar). Here the sodium carbonate has been added, producing a precipitate of sodium ethanoate (sodium acetate) crystals (white), and a temperature drop to 9.6 degrees Celsius, a change of -6.4 degrees from a starting temperature of 16 degrees Celsius (see image: C008/4185).