|
Therefore, the words vapor and gas are often used
interchangeably. Vapor is more frequently used for a substance which, although present in
the gaseous phase at 200C, exists as a liquid or solid at this temperature and
normal atmospheric pressure. We can also say that SO2 (1570C), Cl2
(1440C), NO2 (1580C), and CO2 (2890C)
can be obtained as “vapor” since at 200C they can be condensed as a liquid
by increasing the pressure. Their critical temperature (given in parenthesis) is above 200C.
However, since they are normally purchased in steel cylinders under pressure we usually
refer to them as gases. |