Several different sized flasks were evaluated, but the 25 mL Erlenmeyer flask gave the best results, combining a small size with enough volume of liquid to obtain an easily observable change. A small volume of the test liquid is required to facilitate good heat transfer from the water bath to the liquid inside of the flask.
The temperature of the water bath was lowered rather than increased for simplicity: it is easier to control temperature
changes by cooling with ice chips than by heating the water bath using a hot plate slowly to allow good heat exchange.