On 09/09/2012 21:32, Rick Hughes wrote:
I bought a pH meter which is aimed at gardeners ...
http://www.amazon.co.uk/Gardman-Soil...7222580&sr=8-3


I thought I could also use it on liquids ... but I have serious doubt it
is reading acidity correctly.
Is there a simple way of testing ?

In water it read 7 ..

You are very lucky to get that result it was pure chance. Rainwater
usually has enough CO2 dissolved to be slightly acidic pH 5 and tapwater
is buffered towards alkaline to avoid dissolving the pipes.

(so OK there) ... I tried in in a bottle of white
vinegar with is rated at 5% acidity it reads pH 6

Vinegar is a fairly dilute solution of a weak acid but it should be
about pH 3 or so. You can buy indicator solution or strips of paper for
next to nothing that cover the 0-14 range (or selected ranges). eg

http://www.ebay.co.uk/sch/i.html?_nkw=ph+test+paper

Is there a simple home way of testing calibration ?

Of the things you can likely find on the kitchen/garage shelf. Sodium
bicarbonate, carbonate, ammonia and sodium hydroxide (careful) as bases
in rough order and acetic acid, citric acid (lemon juice), sulphuric,
hydrochloric acid as a strong acids.

Take care with any strong alkali or acid they can be unforgiving.

--
Regards,
Martin Brown