kenneal - lagger wrote:I've just had an email through from
a home shopping website that I get emails from on a regular basis offering alcohol based hand sanitiser at 60% alcohol "as recommended by Health experts" for £4.99 for an 80ml bottle or 4 for £14.97 or 250ml for £9.99 or 4 for £29.97.
The DIY stuff referred to earlier in the thread to WHO spec was 80% ethanol or 75% isopropyl alcohol.
??
Also I have no idea whether this is a good price or not although I'm not bothered about buying any myself.
60% is the lowest alcohol concentration considered acceptable. Commercial products usually contain the minimum as water is cheaper than alcohol.
Very cheap products may contain 60 Chinese percent or about 50% actual.
For home made I would favour about 75% to 80% of alcohol by volume, for several reasons.
Firstly the "pure" alcohol is probably about 94% alcohol and 6% water. So a home made mixture that looks like 750ml alcohol and 250ml water, will in fact contain about 700ml of actual alcohol and 300ml of water (50ml already in the alcohol, and 250ml added by the maker)
So what sounds like a 75% concentration is only in fact 70%.
Measuring the ingredients with the crude equipment most of us have in the kitchen could easily result in the presumed 750ml of alcohol being only 700ml, and the presumed 250ml of water being in fact 300ml,.
Careful use of good quality measuring cylinders or graduated flasks in a lab can give 1% accuracy, but such results can not be expected with a kitchen measuring jug.
Alternatively one might decide not to measure the alcohol, but use one whole bottle, adjusting the other ingredients accordingly. This carries the risk that the 1000ml bottle might only contain 950ml, due to evaporation in storage or transit, or being measured in Chinese ml in the first place.
I DO have laboratory type measuring cylinders, purchased years ago for "just in case" but most of us don't.
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