We describe the construction of a simple solution calorimeter, using a miniature bead thermistor as a temperature-sensing element. This has a response time of a few seconds and made it possible to carry out a thermometric reaction in under a minute, which led to minimal heat losses. Small temperature changes of 1 K associated with enthalpies of solution or enthalpies of neutralization can be measured with accuracy better than 1%. The degree of accuracy depended on how many measurements were made and gave the student an opportunity to think about different sources of error. (Contains 1 figure.)