To a cold solution of 80 g. (2 moles) of sodium hydroxide in 500 cc. of water in a 1-l. flask is added 50 g. (0.266 mole) of gallic acid. The flask is immediately tightly stoppered (Note 1), and the mixture shaken occasionally until all the acid has dissolved; 89 g. (67 cc.) of dimethyl sulfate (0.71 mole) is then added (Note 2) and the flask is shaken for twenty minutes, being cooled by means of cold water in order that the temperature does not rise above 30–35°. Occasionally the stopper is raised to release any pressure. A second portion of 89 g. of dimethyl sulfate is then added and shaking continued for ten minutes longer. During this second addition the temperature may rise to 40–45°.

The flask is then fitted with a reflux condenser and the contents boiled for two hours. In order to saponify the small amount of ester which is produced, a solution of 20 g. of sodium hydroxide in 30 cc. of water is then added and boiling continued for two additional hours. The reaction mixture is then cooled and acidified with dilute hydrochloric acid; the precipitated trimethylgallic acid is filtered with suction and washed well with cold water. The product, which melts at 157–160°, is sufficiently pure for many purposes. It weighs 50–52 g. (89–92 per cent of the theoretical amount). It may be purified by recrystallization from 2 l. of boiling water with the use of decolorizing carbon, the filtration being carried out in a steam-jacketed funnel. In this way 41–43 g. (Note 3) of colorless needles melting at 167° is obtained.