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Posted by John Cochran on June 20, 2008, 2:50 pm
>> Don Young wrote:
>>
>> >>Ok, anybody want to attempt to splain to me why there is both a "pH"
>> >>(6.2-8.4) and a "Total Alkalinity" (0-240 ppm) scale on a pool water
>> >>chemical test strip kit . I have been using the strips that have the 4
>> >>square foam pads on the ~1/4" x 4" plastic strip that you dip in the
>> >>water, wait and then compare the colours change on the pads to the
>> >>reference colours on the label of the strips' bottle. The strips have a
>> >>colour range for Total Bromine (0-20 ppm), Free Chlorine (0-10 ppm), pH,=
>
>> >>and Alkalinity. Granted, it is likely that the strips I currently have a=
>re
>> >>technically past the expiration date, and I will get some new ones soon,=
>
>> >>but firstly just to compare the results of the test between the old stri=
>ps
>> >>and new strips, so I cna finish them off. Any comments on how off they c=
>an
>> >>get with age?
>>
>> >>This is my problem - ngQ(uestion):
>>
>> >>I was taut in skool that pH and alkalinity was the same scale. The numbe=
>r
>> >>is determined from the definition regarding the hydronium ion
>> >>concentration, and math or something like that. The pH of neutral water =
>is
>> >>about 7. That it, it is neither acidic nor base in its chemical characte=
>r.
>> >>If the number is low, like 3, it is "acidic" and if its high, like 9, it=
>
>> >>is alkaline (base). But if it is acidic (low number on the pH scale), by=
>
>> >>definiton it CANNOT be alkaline at the same time, or vice versa: it cann=
>ot
>> >>be alkaline and be acidic too.
>>
>> >>So why are there two scales on these (pool) water test strips, which rea=
>d
>> >>from low to high for both pH and Alkaline? There is a pH and a Alkaline
>> >>scale!? So according to the pool companies you can have a low pH and a l=
>ow
>> >>alkaline pool at the same time, or high & high, or low & high, or high &=
>
>> >>low.
>>
>> >>Because I go to the chemical cupboard for the right chemical to fix the
>> >>problem (assuming all other parameters are being considerately moderated=
>
>> >>too) and I find chemicals labelled "pH Up", "pH Down", "Alkalinity Up",
>> >>and "Alkalinity Down"! And I don't want to do anything, (a) because the
>> >>strips may be wrong (via expiration) or (b) the pool chemical companies
>> >>may be full of crud.
>>
>> >>----=3D=3D Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usen=
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>>
>> > It's been a long time but I seem to remember that Total Alkalinity was
>> > something that built up over time as you kept adding chemicals to adjust=
> the
>> > PH one way or another. At that time I think Total Alkalinity was somethi=
>ng
>> > you wanted to stay as low as possible and when it got too high you had t=
>o
>> > drain some water and replace it with fresh water.
>>
>> > Of course, I could be all wet. ;>)
>>
>> > Don Young
>>
>> You more or less got it right:
>> pH is a measure of the hydrogen ion concentration (lower number is
>> =A0 more acid and more hydrogen ions).
>> Total Akalinity is a measure of the amount of acid you have to add
>> to lower the pH.
>>
>> In very pure water, only a little bit of acid (or a little bit of some alk=
>ali,
>> such as sodium carbonate) will cause dramatic changes in pH.
>>
>> In water with years of pool chemical residues, it can take much more
>> pH adjustment chemicals to make much of a difference.
>> Such solutions might be described as highly buffered.- Hide quoted text -
>>
>> - Show quoted text -
>
>yes...
>
>I look at it this way... if you have say 1 gallon of water and say 10
>grams of acid and 10 grams of base, the pH is neutral and the total
>alkaliinty is low...
>
>but instead if you have 10 pounds of acid and 10 ponds of base, ( I
>exagerate here) the pH is still balanced but the total alkalinity will
>be high.
Interesting chemistry you're using there.
If you mix a base and an acid together until you get a neutral pH, you don't
have a high alkalinity or a high acidity. What you have is a salt solution.
A glass of hydrochloric would rather nasty to drink.
A glass of sodium hydroxide solution would also be rather nasty to drink.
Mix them together until you get a pH of 7 and what you'll have is simply
a glass of water with salt disolved in it. Not the tastiest thing in the world
to drink, but not nearly as bad as either of the original 2 ingredients.
And yes, mixing a base and an acid will always get you a salt. The type of
base or acid you use will determine what salt is produced. And not all salts
are as benign as good old sodium cloride, but they're still just a salt.
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