I've been looking at this a bit. If as the krib states 30mg NaHCO3 in 1 litre gives 1dKH then we'd need 6g of it to raise 5 litres of water to 40 dKH. If though as wikimedia states it requires 50mg then we'd use 5g to raise the 5 litres to 40dKH. This wikimedia figure then is what we have been using. But the strange thing is I've done the calculations and the Krib figure seems to me to be correct. My chemistry has been rusting away for over 20 years so I may have got something wrong here. I'd be glad if someone could shed some light on this.

James