  The dipping source XB 1916-053 is a compact binary system with an orbital
period of 50 min harboring a neutron star. Using ten new {\it Chandra}
observations and one {\it Swift/XRT} observation, we are able to extend the
baseline of the orbital ephemeris; this allows us to exclude some models that
explain the dip arrival times. The Chandra observations provide a good plasma
diagnostic of the ionized absorber and allow us to determine whether it is
placed at the outer rim of the accretion disk or closer to the compact object.
From the available observations we are able to obtain three new dip arrival
times extending the baseline of the orbital ephemeris from 37 to 40 years. From
the analysis of the dip arrival times we confirm an orbital period derivative
of $\dot{P}=1.46(3) \times 10^{-11}$ s s$^{-1}$. We show that the $\dot{P}$
value and the luminosity values are compatible with a mass accretion rate lower
than 10\% of the mass transfer rate. We show that the mass ratio $q=m_2/m_1$ of
0.048 explains the apsidal precession period and the nodal precession period.
The observed absorption lines are associated with the presence of \ion{Ne}{x},
\ion{Mg}{xii}, \ion{Si}{xiv}, \ion{S}{xvi,} and \ion{Fe}{xxvi} ions. We observe
a redshift in the absorption lines between $1.1 \times 10^{-3}$ and $1.3 \times
10^{-3}$. By interpreting it as gravitational redshift, as recently discussed
in the literature, we find that the ionized absorber is placed at a distance of
$10^8$ cm from the neutron star with a mass of 1.4 M$_{\odot}$ and has a
hydrogen atom density greater than $10^{15}$ cm$^{-3}$. (Abstract abridged)
