Originally, exactly as much as a volume of water equal to the cube of the hundredth part of the metre, at the temperature of melting ice. I don't find that terribly helpful. Not many did. That's why, in 1889, the mass of the kilogram was redefined as being equal to the IPK.
Boiling water is also an effective poison ivy killer. If the area where you will be killing poison ivy has no other plants you wish to keep, pour boiling water over the poison ivy plant. Boiling water will kill any part of a plant that it comes in contact with, so be careful using this around desirable plants.
Wash off with dish soap. The toxins from the poison ivy plant are an oil, and therefore wonât be able to be removed completely with just water. Use a dish soap that advertises breaking up oil to wash the affected area. The dish soap should help to minimize the spread of the poison and limit the rash.