CALCULATION OF THE REFRACTIVE-INDEX OF PURE GAS HYDRATES USING A MODIFIED LORENZ-LORENTZ MODEL - APPLICATION TO METHANE HYDRATE

The calculation of the refractive index of methane hydrate is carried out using a modified Lorenz-Lorentz model. The occupancy of methane in to the structure of the hydrate is taken into account. It is calculate d from van der Waals and Platteuuw theory and shows small changes when the experimental pressure varies from 30 to 110 bars and when the exp erimental temperature varies from -3 to + 12 degrees C. We have observ ed great changes of the relative index of refraction with the methane occupancy (the relative index of refraction is the ratio between the r efractive index of the methane hydrate and of liquid water). The relat ive index of refraction characterizes the ability of the methane hydra te particles to scatter the light. Thus, the occupancy factor of metha ne must be taken into account when the calculation of size distributio n uses the optical properties of particles.