[gwrightson]

can some body tell me the correct way to test for the ph,
 have my ph paper , now i know i need distilled water, nobody seems to stock this now !!!!!!!!!!!!
but have got deionised water will this suffice
derick i did see ur demo at the last course , but sorry seems to have been lost in my head some where .
have searched for answers (, to no avail )of correct procedures.
a nice simple explanation , will be welcomed,
geoff

[Mike Halliday]

geoff what do want to test the ph of?, if its a stain then get some paper and test the ph of it then then you have a baseline to work too then add some to the stain and work it in with a spatula then test its ph.

i'm sure this is correct, but some one might say that you need distilled water

Mike

[Dynafoam]

Distilled water is recommended because it will have a pH of 7. Hense when used to dissolve soluble matter from a stain, you will get a true reading.

De-ionised water has been electrically treated to remove mineral contaminants, but some I have tested with a digital meter in not neutral pH (though probably close enough for this purpose)

Another sorce of 'distilled' water is the melted frost from a fridge or freezer.

[Mike Halliday]

I got mixed up : I said 'paper' i meant to say 'water'


why does freezing water alter its Ph?

Mike

[gwrightson]

55 Veiws and replys from 2 people tks mike , tks john,
is it that all rest dont know or is it a stupid question, well mike ill let you show me next time i seee you .
ice now that will be handy, this time of year
geoff

[Doug Holloway]

Geoff,

Deionised water and distilled water will both be O.K for your purposes.
Remember there is an error of 0.5 when using pH papers so any slight difference between deionised and distilled will be irrelevant.

Freezing water purifies it by excluding molecules(impurities) which don't fit in as the crystals form, so the pH will become more neutral.(The impurities may be alkaline forcing up the pH.)

Hope this helps,

Doug

[Shaun_Ashmore]

John where did you get your digimeter from and how much was it?

Thanks Shaun

[Dynafoam]

Hi Shaun,

The portable instrument I use is the Hanna "Checker".

This can be bought from Prochem for about £50, or direct from Hanna Instruments for a little over half that price.

http://www.hannainst.co.uk/acatalog/HI_98103_Checker_.html

You will also require so calibration solutions to set up the instrument - two types Ph 7.01 and pH 4.01. On the page above you will see boxes of 25  which cost £15 each (total 2 x 15 +VAT = £35.25). Do not buy these. They do a mixed box containing 5 of each, stock number HI77400P at a more reasonable price.

One the instrument has been calibrated, use it to check a neutral solution suck as distilled water and an acid such as acid rinse, write down the recorded values and these can then be used for routine maintenance check. the remaining * sachets can be reserved for occasional checks to confirm the pH of your chosen substitutes.

It should be noted that this instrument is designed for testing liquids with a depth of at least 0.25 inches - You cannot press it against a damp carpet and take a reliable reading.