Fractionally

[Sarah]

By fractions or separate portions; as, to distill a liquidfractionally, that is, so as to separate different portions.

[Tariq Zaki]

1: of, relating to, or being a [fraction]
2: of, relating to, or being [fractional] currency
3: relatively small : INCONSIDERABLE
4: of, relating to, or involving a process for separating [components] of a mixture through differences in physical or chemical properties