Calorimetry progress report

The constant temperature bath is in operation. A ballistic type instability was detected in the calorimeter circuits and corrected by grounding the bath. Calorimeters 37, 39, 40, and 43 have been installed are now being run. Calorimeter 40 was found to be unstable, and is to be disassembled and examined for the trouble. Calorimeter 46 was finished and placed in operation. Construction details are discussed. Six Logac samples were run in Calorimeter 38. Tests of this calorimeter are in Table 1. Comparison of Calorimeter 38 in a water bath and in an ice bath is shown in Table 2. Good results were obtained for such a drastic change in environment. Calorimeter 38 was turned over to Calorimetric Assay marking the end of the tests of this particular microcalorimeter. Calorimeter 44 was completed and installed in the ice bath. Table 4 shows the results of tests. The zero bridge potential is small and is very stable compared to Calorimeter 38. The comparison of the values with those from Calorimetric Assay is summarized in Table 3. The characteristics of Calorimeter 44 are shown in Table 5. Construction details are given for the platinum-manganin bridge-type thermometer. An instrument was needed that could be used to detect bath temperature changes of the order of 0.0005 C. The thermometer was installed in the bath on March 29, 1949. With the bridge current at 10 milliamperes, the measured sensitivity is 2.5 microvolts per 0.001 C change in temperature. The temperature difference between the inner and outer walls of a quartz capillary containing polonium was calculated. The volume of polonium in the capillaries was recalculated and the density re-evaluated