NEAR-INFRARED STUDY OF THE LIGHT LIQUID ALKANES

A cryostat cell has been designed and constructed to enable the in sit u liquification of methane, ethane, and natural gas from the mains. Th is cell, which was operated with pathlengths of 3 mm and 62 mm, was us ed to study the near-infrared spectra of methane, ethane, propane, n-b utane, n-pentane, n-hexane, n-heptane, liquified mains gas, and bulk s torage liquid natural gas (LNG) over the range 3000 to 15,000 cm(-1) w ith a resolution of 8 cm(-1). Band positions and their extinction coef ficients corresponding to overtone and combination bands have been obt ained for the first time under standard conditions. It was shown that significant differences are seen between the spectra of methane and et hane, and hence their relative concentrations can be estimated in the different samples of LNG, while the concentrations of the longer chain alkanes are so small and their spectra so similar that it would be im possible to determine their individual concentrations in the LNG sampl es without the aid of chemometric manipulation.