  The measurement of the apsidal motion in close eccentric massive binary
systems provides essential information to probe the internal structure of the
stars that compose the system. Following the determination of the fundamental
stellar and binary parameters, we make use of the tidally induced apsidal
motion to infer constraints on the internal structure of the stars composing
the binary system HD152219. The extensive set of spectroscopic, photometric,
and radial velocity observations allows us to constrain the fundamental
parameters of the stars together with the rate of apsidal motion of the system.
Stellar structure and evolution models are further built with the Cl\'es code
testing different prescriptions for the internal mixing occurring inside the
stars. The effect of stellar rotation axis misalignment with respect to the
normal to the orbital plane on our interpretation of the apsidal motion in
terms of internal structure constants is investigated. Made of an O9.5 III
primary star (M1 = 18.64+/-0.47M${_\odot}$, R1 = 9.40+0.14-0.15R${_\odot}$,
Teff,1 = 30900+/-1000 K) and a B1-2 V-III secondary star (M2 =
7.70+/-0.12M${_\odot}$, R2 = 3.69+/-0.06R${_\odot}$, Teff,2 = 21697+/-1000 K),
the binary system HD152219 displays apsidal motion at a rate
(1.198+/-0.300){\deg}yr-1. The weighted-average mean of the internal structure
constant of the binary system is inferred: k2 = 0.00173+/-0.00052. For the
Cl\'es models to reproduce the k2-value of the primary star, a significant
enhanced mixing is required, notably through the turbulent mixing, but at the
cost that other stellar parameters cannot be reproduced simultaneously. The
difficulty to reproduce the k2-value simultaneously with the stellar parameters
as well as the incompatibility between the age estimates of the primary and
secondary stars are indications that some physics of the stellar interior are
still not completely understood.
