b.all wrote:with the readings you've got it's certainly possible to work out the strength. hope this helps:
firstly work out the strength you've got in the initial fermentation before you topped up with water simply using the gravities. then you have 17.5 litres of a certain percentage alcohol to which you add 5 litres so you can get both the strength you've diluted it to as 17.5/22.5 times what it was before and the gravity is also reduced by diluting. pure water is 1.000 so you have 5*1.000 plus 17.5 times your gravity at the point which is all divided by 22.5 to give you the gravity after dilution. if their has been a gravity drop from that to your final gravity then you need to work out what extra alcohol content has been added b using the usual formula.i wouldn't be surprised if no more fermentation occurred after you topped up.
an alternative and simpler method which should yield the same result is to work out what your starting gravity would have been if you had made it to 22.5 litres using a similar calculation to the gravity calculation i mentioned earlier. after that you can just use a normal alcohol calculation from your calculated original gravity and you measured final gravity.
