The IR absorption spectrum of mixtures of GH₄ with Kr in the range 800-6000 cm^-1 is studied in the region of the gas-liquid and liquid-crystal phase transitions. It is found that, as the system density increases, the ratio of the v₄ band intensity to that of the v ₃ band becomes larger and the measured values of the second spectral moment of the v₄ band become smaller than the corresponding calculated values. The quantum counterpart of the generalized J-diffusion model was used to describe the shape of the v₃ and v₄ bands, and the rotational relaxation times of CH₄ in solutions were obtained. It was shown that, as the density increases, a broad 1470-cm ^-1 band appears in the region of the "forbidden" (induced by a Coriplis interaction) v₂ band (v_Q = 1535 cm ^-1) detected in a low-density gas. The intensity of this band is appreciably higher than that of the v₂ band.