MELTING-POINT OF CARBON
Carbon and arsenic are the only two elements that have a melting-point above the boiling-point ; and among compounds carbonic acid and fluoride of silicium are the only other bodies with similar properties. Now the melting-point of arsenic is about 1-2 times its absolute boiling-point. With carbonic acid and fluoride of silicium the melting-points are about i-i times their boiling-points. Applying these ratios to carbon, we find that its melting-point would be about 44000.
Therefore, assuming the following data :
Boiling-point..............38700 Ab.
Melting-point..............44000
Critical temperature.......5800°
Critical pressure...........2320 Ats.
the Rankine or Van der Waals formula, calculated from the boiling-point and critical data, would be as follows :
log. P=io-ii-39120/T,
