3种测量石蜡比定压热容实验方法的比较

Comparison of Three Methods Measuring Heat Capacity of Paraffin

用差示扫描法、气相色谱法和水浴法对石蜡的比定压热容进行了测量。差示扫描法可以给出石蜡比定压热容的精确值。气相色谱法通过测量各烷烃的质量分数，可较准确地对液态石蜡的比热容进行测量。相对于差示扫描实验的结果，误差小于3．9％，用这种方法测量固态石蜡的比热容存在较大误差。水浴法可对固态石蜡的比热容进行较准确的测量，误差小于3．5％。用该法测量液态石蜡的比热容时，必须对水浴上方存在液态石蜡时的散热进行准确测量。

Differential scanning calorimeter（ DSC ）, gas chromatography （GC） , and adiabatic bath are employed to measure heat capacity of paraffin respectively. DSC provides precise values of heat capacity for both solid and liquid paraffin. GC gives mass fractions of alkanes in paraffin, which can generate heat capacity combined with a proper mix nile. Compared with the results of liquid paraffin given by DSC, relative errors of results given by GC are less than 3.9%. Melting of iso-alkanes occur during heating of solid paraffin, that causes problems in measuring heat capacity of solid paraffin by this method. Relative errors of heat capacity of solid paraffin measured by adiabatic bath are less than 3.5%. When paraftin is at liquid phase, heat release of the bath to surroundings must be carefully calibrated.