Cannot take a subsample of a solution

[GeertD]

Hi,

First of all, two thumbs up for this great library!
It greatly enhances working with PhreeQC.

I'm mixing solutions:
sol3 = sol1*0.8 + sol2*0.2

This works fine, but one has to keep the sum of the fractions = 1, otherwise the new solution has a mass > 1.0, which makes it harder to interpret the species amounts (all in mol):

sol3 = sol1*8.0 + sol2*2.0
sol3.mass
>> 10.0

I thought easy as, we'll just take a subsample to get to water mass = 1.0 again:
sol3 = sol3 / sol3.mass

No errors, but:

sol3.mass
>> 10.0 (no change)

I had a look at the code (solution.py), and the magic div() method only changes sol.factor, it does not mix to create a new solution (subsample).

An rather ugly workaround:

sol_empty = pp.add_solution({'-water': 0.0})
sol4 = sol3*0.1 + sol_empty
sol4.mass
>> 1.0

This triggers the mixing of the solutions, and adds an dummy empty solution.

It would be much more intuitive if multiplying a single solution with a factor would actually change the solution amount (instead of the internal solution.factor).

Best regards,
Geert