Abstract: A temperature measuring device useful for measuring the temperature of urine samples is disclosed comprising a solid solution having incorporated therein a nucleating agent and an indicating dye system. The preferred solid solution is a mixture of ortho-chloronitrobenzene and ortho-bromonitrobenzene. The preferred dye systems are pinacyanol iodide and a mixture of bromcresol purple and ethyl red. A novel aspect of the thermometer is that it is adapted to indicate a predetermined temperature at an observable initiation of melt temperature which is about 0.3.degree. to about 1.9.degree. F. below the completion of melt temperature of the composition. The thermometer is a real time device.