Experimental Fusion Curves of Indium and Tin to 105 000 Atmospheres

The experimental fusion curves of indium and tin have been determined to a pressure of 105 000 atmospheres. The melting point was detected at various pressures by means of a sharp increase in the electrical resistance of the sample, which gave rise to a sudden increase in the sample temperature. The melting temperature of indium was found to rise smoothly from a normal value of 156°C to a value of 417°C at 105 000 atm. The experimental data are fitted very well by the Simon equation $\frac{P}{a}={\left(\frac{T}{T_0}\right)}^c-1\mathrm{}$, with $a=15\mathrm{}000$ atm, $c=4.34\mathrm{}$, and $T_0=429\mathrm{}°$K. No evidence of polymorphism is observed. A phase transition is found for tin, with a triple point on the fusion curve at 38 000 atm, 318°C. The melting temperature for the first phase rises smoothly from its normal value of 232°C to the triple point, and the data are fitted very well by the Simon equation with $a=7400\mathrm{}$ atm, $c=11.3\mathrm{}$, $T_0=505\mathrm{}°$K. The melting temperature for the second phase rises smoothly from the triple point to a value of 500°C at 105 000 atm, and the data are fitted very well by the Simon-type equation $\frac{(P-38\mathrm{}000)}{21800}={\left(\frac{T}{591}\right)}^{5.25}-1\mathrm{}$. The uncertainty is estimated to be approximately ±5% in the measured melting temperature, ±5% in the pressure calibration, ±20% in the Simon coefficient $a$, and ±2% in the Simon exponent $c$.