A semi-empirical approach to the critical analysis of thermodynamic data is proposed and applied in this work. A critical analysis of heat capacities of the sixteen isostructural A

III

B

V

compounds was then made based on the correlative optimization method. A set of mutually agreed equations C

o

P

=a+b·10

-3

·T-c·10

5

·T

-2

was proposed to describe the heat capacities of these phases. Two continuums of relations C

o

P

(T) vs. logarithm of the sum of atomic numbers of elements A and B were obtained for the A

III

B

V

phases

of both sphalerite and wurtzite types

in the temperature range from 260 to 1 500 K. Based on the proposed equations

heat capacity values were predicted for the previously unstudied (or poorly studied) phases TlN and AlP within the temperature ranges of 260~1018 K and 260~1 500 K

respectively. The proposed correlative method of thermodynamic functions can be applied to other inorganic and organic isostructural compounds

other different groups of isostructural organic and inorganic compounds.