[billnotgatez]

If you are trying to learn chemistry you have to do some of the tedious with the provocative.
You would learn an important chemistry technique if you did some titration.

[Ballistic]

Yes, what you say is right, but at my age I don't have time or energy and I work round the clock and I have done titrations on a small scale.

What I did was label the Sodium Carbonate solution and abandon it for later and then I made 500ml of B's solution assuming the Sodium Carbonate is Anhydrous, and it all dissolved and the product tested fine. (There were a couple of globules of white powder in the bottom which I already knew must be Sodium Bicarbonate from all the reading I had been doing about this - it's where the old Sodium Carbonate had picked up some CO2)

Incidently, the 2 litre bottle I have of the Sodium Carbonate which hadn't fully dissolved, as I previously said had formed crystals in the bottom (which from the description I believe are mono-hydrate crystals) but when this was shaken up at a different temperature and time of day and left over night then formed a much larger depth of what I believe / guess are un-dissolved decahydrate crystals. And I hypothesise that the solution can stop in different "phases" where the temperature was insufficient to dissolve different hydration states of the Sodium Carbonate which have different temperatures required to fully dissolve them. Some of this is just guess work I must add.