# What is the definition of the “solar mixing ratio”?

What is the definition of the "solar mixing ratio"?

Specifically, I'd like to know why the ratio of H2 and He is 0.84 and 0.16 at the "solar mixing ratio" as shown in Table I in The Galileo Mission.

The mixing ratio is the ratio of the number of moles of species $$x$$ to the total number of moles in the gas considered. i.e. it is a ratio of number densities.