This thesis is presented in two parts. In the first part, an attempt has been made to evaluate the possibility of application of gas sampling probes for kinetic and mixing studies of reacting, high velocity, high temperature gas streams.

A water cooled, constant area type of probe has been proposed and its internat aerodynamics have been analysed theoretically on the basis of a one dimensional model considering both frictional and heat transfer effects.

Quenching rates of the sampled gas have been obtained considering free stream Mach numbem 4, 3 and 2.

From the quenching rates, quenching efficiencies of the probe were determined by considering sampling from a H₂-O₂-N₂ reaction system.

From these theoretical analyses it has been concluded, that when sampling from a high velocity, reacting gas stream, quenching by convection alone is insufficient to freeze the sample within the sampling time and expansion and dilution of the sample are necessary.

The second part of the thesis deals with an experimental determination of the composition profiles of an open, rich, CH₄-O₂ flame and interpretation of the profiles in terms of chemical kinetics.

An atom balance, along the flame axis, obtained from the experimentally determined composition profileshas given reasonably satisfactory results and indicated that there are no large errors in the data as a whole.

Kinetic interpretation of the data has shown that CH₄ disappears predominantly by reaction with H atom, in the primary reaction zone of a rich flame.

An experiment to determine the radical concentrations has been suggested.