Is your lye KOH or NaOH?

You may have found a source of lye but are not sure if it is KOH or NaOH. You will need to know which form you have, if you want to use it in the correct quantity in chemical reactions such as the conversion of glycerides to biodiesel.

A simple test is to hold a small sample of the lye in a flame, and see what colour the flame has.

Get a glass bowl and put a drop of water in the middle. Add a little lye to the drop of water, about the same amount of lye as there is water.

Dip the eye of a needle in the lye/water drop and stir around to dissolve the lye in the drop of water.

Try to get a drip of lye solution to stick to the eye of the needle, and hold the drip in a gas flame. This is best done in a darkened room so you can see the colour of the flame more clearly.

Compare the flame to those below, to help you decide whether you have NaOH or KOH




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Graham Laming