The construction and operation of an all glass ice calorimeter which allows the rapid and moderately precise (approximately 0.5%) measurement of heat changes in a system is described. In addition to the usual advantage of an ice calorimeter of being able to measure slow heat changes, the instrument described here is extremely simple to construct and operate. The use of a calibrated capillary tube to determine the volume change due to melting or freezing of ice eliminates the need of an analytical balance and simplifies operation of the instrument.