The second thermometer, which was calibrated in July, 1970, 
has a resistance given by 
oe ie) 
The latter has been used in the study of all salt solutions 
except chose of Nae andi kG ihe fthermometer has tour, 
leads directly connected to.a Mueller bridge which, for 
resistance changes less than one ohm, have an accuracy of 
0.00001 ohm. All resistances are measured in accordance 
with calibration procedures of the National Bureau of 
Standards and recorded by a Leeds and Northrup Speedomax W 
recorder. The bridge is maintained at 34.8°C by a constant 
femperature Control unit: | Atul) Sensitivity, 1t 15 
possible to read the scale of the null detector to 0.0002°C. 
P25 5590) Cl OMRON SIS2850R°-h0.5750) x 10) 
Experimental Procedure 
Galaibrationexnuns: based on the heat capacity data for 
pure water by Osborne et al. (3) the heat capacity of the 
bomb calorimeter is determined. 
The bomb calorimeter is first filled with an accurately- 
weighed quantity of distilled water. Then, starting from 
80°C and with a progressive interval of 20°C, heat capa- 
cities are measured to 200°C. Depending on the reproduci- 
bility of the data, sets of runs are repeated from four to 
Six times. A least squares smooth straight line is fitted 
through the data which is finally used in the computations 
Obeehe) heat capacities of any ot the salt solutions under 
study. 
Along with the calorimeter heat capacity, another item 
of information obtained during calibration is the hypothe- 
tical finine tame. has) ws necessary in heat «capacity 
measurements because there is heat transfer during the 
heat-input, period and the input time is far from instanta- 
neous. The usual procedure for determining the hypothetical 
firing time is extrapolating both the heating and the 
coolang curves to a certain time, to, at which time the 
ancas Jlfand= 2 in -roure j/ are’ equal . 
hypacal-calibrativon results sare presented in Tabile 1 
for both the heat capacity of the calorimeter and the 
hypothetical firing time. Here K equals heat capacity of 
the calorimeter and to is in minutes. 
