In order to calculate the kinetic coefficients of solutions it is necessary to find the distribution function in the solution, in the presence of small gradients of the thermodynamic functions and the velocities. Obviously, this problem can only be solved for weak solutions, when the impurity excitations may be treated as an ideal gas. We shall limit our considerations to the phenomena of diffusion and thermal conduction, which are intimately linked with one another, as can be seen from Eq. 24-60. Together they determine the heat transfer properties of solutions. The kinetic equation determining the distribution function f of the excitations in the solution, has the usual form of Eq. 18-1. () ∂ n ∂ t + ∂ n ∂ r   ·   ∂ H ∂ p − ∂ n ∂ p   ·   ∂ H ∂ r = ℐ ( n ) https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780429502897/a3547081-d1fe-4ca8-9f19-7cf8caff9ba3/content/eq820.tif"/>