To a 1 L flask add 152 g of gamma-aminobutyric acid, 104 g of sodium nitrite and about 350 mL of water with vigorous stirring. Place the flask in an ice bath. After the solution is clear start adding 500 mL of conc. HCI at a rate of 2 drops per 3 seconds. Do not allow the evolution of nitrogen oxides to become too vigorous. After the addition extract the gamma-hydroxybutyric acid with 4x 250 mL portions of DCM, distill the DCM off. Distill the crude GHB under vacuum.