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Re: T.D.S.

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Posted by Andy on August 02, 2002 at 17:22:45:

In Reply to: Re: T.D.S. posted by BoilingMan on July 30, 2002 at 12:00:54:

: : While preparing a sample of boiler water from a 60 bar boiler to take a tds,the water is cooled and then neutralised. Now my question is that i am neutralising with a powder (Galic Acid),now i understand that this neutralising is to drop the pH of the water from pH 10.2 to around pH 8.3 ,the point where phenolphaelin colour dissapears,so having reduced the OH ions to reduce the conductivity ,Ok so how is it i am disolving a solid powder into my water and it doesn't affect the dissolved solids reading.????? it is a solid and it has just been disolved.
: : Double checking the tds reading using N/10 sulphuric acid to neutralise the solution gives same tds reading.
: : Using the finished sample from the total alkalinity test (pH 7) gives the same result.
: : Some people say its because its a buffer solution,but how can that be when as an acid it will reduce the pH of the solution below 7 and add H ions making it acidic.
: : If anybody can explain this little puzzle to me i would be grateful as it has been puzzling me for a few years.
: : Thanks in advance
: : Andy

: NOW!

: Don't be confusing with ions and other things.
: Every things are more simple.
: By neutralising the water sample we just simple substracting that part of chemicals, which we contributed as a treatment.

: Because real water in the boiler consists of Ca,K, Na, other "nutritions" dissolved in the water and chemicals which we introdused to it.
: Therefore w/out neitralising your reading will be much higher.BTW I did check it in my boiler w/out and with neutralising it was 2500 ppm and 1400 ppm accordingly.
: Therefor don't be confusing with powdered
: gallic acid,because it is "solid"!!!

: Hope, i helped you and myself as well!

Thanks BoilingMan,

I am using Drew Ameroid's UltraMarine boiler water system.

I did a little research and found out the name for gallic acid 3,4,5 trihydroxybenzoic acid.

I understand that we are looking for
sodium chloride, magnesium chloride, magnesium sulptate,calcium sulphate, calcium bicarbonate etc etc....and that we look at the resistence to tell us how much disolved solids are present (micro ohms)or infact the inverse of that reading (micro mhos).

I still don't see how disolving this solid does not increase the TDS, unless the constituants of this acid do not conduct electricity. Which is hard to believe. C6H2(OH)3COOH.H20 is its formula after it disolves.

I think i'll post this question in a chemists forum, as i think its more of a question for them, than for a low'ly engineer.

Anyway Thanks for your help


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