Ole says above"Think you could change the recipe to give 1000ml final solution? It would be a lot easier for those of us who put the finished solutions in 1000ml (or 100ml, in my case) bottles. "

That's what I was driving at when I suggested 769g with water to make 1000mL, based on Sandy's figure of 1kg pot carbonate plus 1Litre water to make "approximately" 1.3Liter. If it's hard to get all of the pot carbonate to dissolve (sounds like a possibility) i'd be tempted to make up half strength part B and use 2x as much (as I do with PMK, since I found it impossible to get the full amount of metaborate to dissolve in the required amount of water)