Has anyone measure the strength of the force of gravity in relation to the molecular bonding?

It's clear to me that gravity it a function of mass. It is also clear to me that gasses are less affected by gravity. So I'm thinking that there exists a measurable minimum binding distance $d$ between molecules that determines whether the molecules will collectively experience a gravitational pull.

In other words, for the same element molecules $M_1$ and $M_2$ the gravitational force is normally represented by the addition of both masses ($M_1 + M_2$). But when $M_1$ and $M_2$ exceed a distance $d$ of separation, the mass used to determine the gravitational force is just $M_1$ or $M_2$. Then if there were a molecular bond that separates the molecules by a distance greater than $d$, gravity could be nullified.

Is this possible or am I totally off base?