Hand Hygiene

Ethanol content in disinfectants

Volume and mass percentages differ
5/17/2022

How is the ethanol content specified?

Ethanol is a frequently used active ingredient in alcohol-based hand disinfectants and other products. When indicating the active ingredient content in percent, the additional indication of whether it is mass percent % (w/w) or volume percent % (v/v) is crucial. This is because 80 g ethanol per 100 g product does not correspond to the same content as 80 ml ethanol in 100 ml product. The ethanol content of all HARTMANN products is given in mass percent % (w/w).

Why do volume percentages and mass percentages differ?

The reason for this difference is a special feature when mixing ethanol with water: the so-called volume contraction. This means that mixing 50 ml of ethanol with 50 ml of water does not produce a volume of 100 ml as expected, but less. One can imagine this phenomenon as the molecules of ethanol and water mixing together more closely than with pure ethanol or water. Cavities between bigger molecules are being filled with smaller molecules.

Can you convert volume percent to mass percent?

The following table compares different ethanol concentrations in volume and mass percent:

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