SYNTHESIS OF PYRUVIC ACID

• Grind together in a glass mortar 200g (1.33 mol) of powdered tartaric acid and 300g (2.2mol) of freshly fused potassium hydrogen sulphate to form an intimate mixture. 

• Place the mixture in a 1.5-litre round-bottomed flask, and fit the latter with a still-head and a long air condenser. 

• Heat the flask in an oil bath maintained at 210-220 °C until liquid no longer distils over. 

• If foaming is considerable and there is danger of the mixture frothing over, heat the upper part of the flask with a free flame. 

• Fractionate the distillate under reduced pressure and collect the pyruvic acid at 75-80 °C/25mmHg. The yield is 60 g (51%).