the convenience store at the corner gas station is likely open.Coincidentally, the methanol that I have is also sold as fuel line antifreeze. I'd forgotten that they've migrated to IPA, because methanol causes problems with fuel injectors. I'll have to check out the auto supply store as soon as they're open for business again.
It's not that easy to do when there's not a big difference between between the SG of the two components. However, I decided to give it a shot, using a digital kitchen scale with a resolution of 1 gram, and a 150 ml graduated cylinder. The SG came out to 0.967, which is just barely within the range of my hydrometer after all. So, measuring it with the hydrometer, I get SG of 0.972 which should be more accurate than the scale method.You can work out the S.G. and hence the percent alcahol the old way, weigh a known volume. If you're not certain of a volume then weigh empty and filled with water. Should be a doddle for a man of your caliber.
I'm not sure I'd call 50£/5 liter bottle "available". It is IPA! not extra virgin olive oil from a remote Greek Island.IPA still seems to be readily available on ebay.
Isopropanol 99.9%, used widely as a solvent and as a cleaning fluid. Isopropyl alcohol removes smudges, dirt, and fingerprints from phones and tablets. Isopropyl alcohol, commonly referred to as IPA or rubbing alcohol , is a flammable, clear, colourless liquid with a slight alcoholic odour.www.ebay.co.uk(IPA ISOPROPANOL). Use as a hand sanitiser is discouraged as it can be painful and causes chapping. to make 70% solution the proportions 4 to 1 . for example for 1 l 99.9% IPA you need add 250 ml distillate water.www.ebay.co.uk