Hydrogen Peroxide 10 %: the 3 % Solution Evaporated in Air at 75 °C, Checked with Permanganate (Thorpe 1912)

Water evaporates faster than hydrogen peroxide, so warming a weak solution in open air makes it stronger. Thorpe gives 75 °C for this first stage; we stop at 10 %, checking the strength with permanganate. Result: hydrogen peroxide of about 10 %. Source: Thorpe, Dictionary of Applied Chemistry, vol. 3 (1912), Hydrogen peroxide. Thorpe takes it on to 20 %; stopping at 10 % is ours. Danger: 10 % peroxide burns skin and eyes. Picture drawn by Youblob.