The flask is set in a water bath and equipped with a thermometer and mechanical stirrer.
"Organic-Syntheses"
Conant, James Bryant
The phenylacetic acid may also be made by boiling under a reflux condenser for eight to fifteen hours, without a stirrer, but this method is not nearly so satisfactory as that described in the procedure.
"Organic-Syntheses"
Conant, James Bryant
Only a very efficient stirrer, which draws down the surface of the liquid, is able to combat this difficulty.
"Organic-Syntheses"
Conant, James Bryant